Propagation, Planting Methods and Cultivation Management of the Plant Wedelia trilobata
Chuandilong is Wedelia trilobata. Wedelia trilobata, also known as three-lobed Wedelia, Dijinhua, and Chuandilong. Asteraceae, Latin name: Wedelia trilobata. Perennial herbaceous plant, native to tropical America. Commonly propagated by cuttings and division.
It is robust by nature and greens up quickly. It not only stabilizes soil and water but also suppresses weed growth with excellent results; however, it does not tolerate trampling and easily harbors snakes and rodents.
Propagation is easy; simply take stem and leaf cuttings and they will root. It is mainly propagated by cuttings; the method is to use branches and stems as cuttings; apart from the cold season, it can be propagated at any other time. Autumn sowing is often carried out after mid-to-late September: substrate disinfection. To disinfect the substrate used for sowing, the best method is to heat it in a wok. The cutting substrate is the nutrient soil, river sand, peat soil, or similar material used for cuttings. For home cuttings, ideal cutting substrate is hard to obtain due to limited conditions, so it is recommended to use the ready-mixed and disinfected cutting substrate provided by this site; medium-coarse river sand can also be used, but it must be rinsed several times with clean water before use. Do not use sea sand or river sand from saline-alkali areas, as they are unsuitable for the growth of flowering plants.
Lingnan Bonsai Cultivation and Management Techniques
(1) Tools
① Scissors. Scissors used for potted trees include spring scissors, long-handled scissors, and small scissors. Spring scissors are mainly used for pruning branches and roots, long-handled scissors for trimming fine branches and leaves, and small scissors for clipping and tying. All scissors must be sharp and sturdy.
② Hammer. There are wooden hammers, small iron hammers, etc., mainly used for processing tree stumps.
③ Crescent chisel. Mainly used for processing saw cuts and scars on trunks and for gouging and digging into tree bodies to give them a rugged, weathered appearance.
④ Saw. There are ordinary woodworking hand saws and hacksaws; the most convenient to use is the dovetail saw. Mainly used for sawing off thick trunks and thick roots.
⑤ Pliers. Ordinary electrician's pliers. Mainly used for binding wire.
⑥ Knife. Includes grafting knives and ordinary small knives. Mainly used for trimming and cutting branches and trunks during grafting.
⑦ Small garden trowel. Mainly used for shoveling soil, mixing soil, and blending mud when potting, as well as for lifting seedlings, transplanting, and digging holes.
⑧ Bamboo stick. Used when repotting to loosen the soil around the pot and remove excess soil from tree roots; used when planting potted trees to firm the root soil; used when cutting branches and stems to dig planting holes to prevent damage to the base of the cuttings.
⑨ Watering can. There are large, medium, and small swivel-nozzle watering cans; sturdy and lightweight ones are preferable. Mainly used for watering; with the nozzle removed, it can also be used for applying liquid fertilizer.
⑩ Sprayer. Used for moistening the stumps of newly planted trees, spraying the leaves of potted trees, and spraying liquid pesticides.
Fertilizing vessels. Includes buckets, small ladles, watering cans, etc.
Sieves. There are bamboo and metal types, divided into large, medium, and small according to mesh size. Metal ones are the most durable.
Boxes. Various empty wooden boxes are used to cultivate seedlings, hold potting soil, and store various small tools and sundries.
Miscellaneous items. Cloths for cleaning vessels, brushes for scrubbing branches and trunks, iron wire, steel wire, hemp twine, and plastic tape for tying branches of various thicknesses, etc.
Chemicals. Trichlorfon, dichlorvos, dimethoate (Rogor), phosmet, and other chemicals for pest control.
(2) Temperature
Temperature is one of the main conditions for plant survival. The growth, development, and all life activities of plants require a certain amount of heat; without suitable temperature conditions, various plants cannot survive. Plants generally can grow within the range of 4 to 36 degrees Celsius, but their temperature requirements are not all the same. Some plants prefer low temperatures, some prefer moderate temperatures, and some prefer high temperatures. Within a certain range, the higher the temperature, the more vigorous the photosynthesis; between 10 and 35 degrees Celsius, for every 10 degrees Celsius increase, respiration increases threefold, and appropriately lowering the temperature can delay plant growth. However, above or below a certain temperature, plants cannot survive. During high-temperature seasons, plant transpiration is high; if water supply is insufficient, plant cells will lose a large amount of water and wilt. As air temperature rises, soil surface temperature rises accordingly, directly hindering root growth, which is also one of the causes of plant wilting. If the temperature exceeds 50 degrees Celsius, plants will lose their vitality because the proteins in their bodies coagulate. When the temperature drops to freezing point or below, the tissues within the plant body will also freeze; at this time plant cells lose water, proteins precipitate, and the plant dies because metabolism stops. This phenomenon can sometimes be seen from the exterior of frozen plants, such as leaves becoming hard, bark frost-cracking, and separation of bark from the woody part. In the Guangzhou area, the average annual temperature is about 22 degrees Celsius; therefore, potted trees in the Lingnan region are suited to growing between 20 and 35 degrees Celsius.
(3) Light
Light is a necessary condition for photosynthesis in all green plants and is also the source of energy for green plants. Within a certain range, the more hours of light, the greater the photosynthetic amount of the plant, and the more organic matter and energy accumulated in the plant body. This has a direct impact on plant germination, growth, and the transition from the vegetative stage to the flowering and fruiting stage.
The intensity of light can also cause a series of complex changes in other ecological factors, causing changes in atmospheric and soil temperature, humidity, etc., thereby indirectly affecting many physiological processes of plants. For example, light increases the permeability of plant protoplasm and has a direct or indirect effect on plant transpiration.
However, different regions and different tree species have different light requirements. Some tree species do not need strong sunlight, while others must grow in an environment with ample sunlight.
According to the adaptability of plants to the length of light duration, plants can be divided into short-day plants and long-day plants. Plants native to temperate or cold zones are mostly long-day plants, while plants native to tropical and subtropical zones are mostly short-day plants. Long-day plants need more than 12 to 18 hours of light per day to flower; if the light is short and the night is long, they will only grow lush branches and leaves but will not flower. Guangdong is located in the high-temperature, rainy tropical and subtropical zone; the difference between the four seasons is not very obvious, winter is shorter and warmer, and plants can grow almost all year round. Therefore, for Lingnan tree stumps cultivated for foliage, flowers, and fruit, as long as there are about 8 to 10 hours of light per day, the plants can have luxuriant branches and leaves and flower and bear fruit. Thus, we should, according to the type of potted tree, adopt different lighting methods and light exposure times, and regularly move the potted trees to promote their growth.
(4) Air and Wind
Oxygen and carbon dioxide in the air are of great significance in plant life; they are indispensable components for plant photosynthesis and respiration and are necessary conditions for plant life. However, in large cities and industrial areas, toxic gases such as chlorine, hydrogen chloride, sulfur dioxide, and nitrogen dioxide emitted from the chimneys of various factories have a certain impact on the growth of potted trees. In addition, dust falling on leaves can clog stomata and hinder gas exchange in the leaves, which is unfavorable for plant respiration; moreover, when dust covers the leaf surface, it also reduces the intensity of plant photosynthesis. The main protective measure is to spray and wash the leaf surface in combination with morning and evening watering.
The influence of wind on plants has both favorable and unfavorable aspects. Wind can often accelerate the transpiration of potted trees. If the wind speed is too high, not only does water evaporate too quickly, but it can also break branches or blow over potted trees, causing losses. Therefore, when the wind is too strong, potted trees should be moved. If they can be placed in a well-ventilated spot, it will benefit the plants; this can not only regulate the air, lower the temperature, and help plants transpire naturally, but also prevent pests and diseases.
(5) Soil
The relationship between soil and plants is both close and complex. Except for a few parasitic plants and floating aquatic plants, the vast majority of plants grow in soil. Soil is not only the place that anchors plants but also the supplier of water and inorganic salts necessary for plant life. Soil air is also an indispensable factor for plant growth and development; it has direct or indirect effects on the respiration of plant roots, the physiological functions of the whole plant, the types and quantities of soil microorganisms, and the nutritional status of plants. The water content and temperature in the soil also have a great influence on plant life.
Soil is a complex whole; it contains mineral soil particles, organic matter, inorganic nutrients, and various different substances, as well as soil microorganisms and the products of their activity - humus - and water and air, etc. All these components in the soil and their interrelationships affect the properties and fertility of the soil, thereby affecting plant life and its geographical distribution.
The soil for planting potted trees must have good air permeability and drainage. As we know, plant roots, in addition to absorbing water and nutrients from the soil, also need oxygen in the soil, so potted soil is suitable for use in combination with several granular soils that have good air permeability and drainage. In addition, the soil should also have water retention. So-called water retention means that the gaps between soil particles can fully retain water. Soil that has air permeability, drainage, and water retention is ideal granular soil.
In addition to having air permeability, drainage, and water retention, potting soil should also be selected and mixed appropriately according to different tree species. Because different tree species have different soil requirements, some like fertile soil, some like loose mountain soil, some like acidic soil, and some like alkaline soil, so the soil quality for potted trees must be carefully selected and mixed.
There are many types of soil used for potted trees, and the vast majority of soils are suitable for use. However, some soils that are too sticky are not suitable for use alone because their gaps are small and drainage and air permeability are poor. Several commonly used potted soil properties are listed below for reference.
① Pond soil. Pond soil is mostly dug out from ponds that have been drained after growing watercress, water spinach, or fish. The dug-out mud is placed on the bank, spread flat, and dried in the sun, made into mud bricks about 15×20 cm, and crushed for use after completely drying. Pond soil is relatively fertile and suitable for the vast majority of potted trees. These mud bricks are available for sale in flower and plant shops.
② Mountain soil. Mountain soil is the natural leaf mold soil of mountain forest areas. After long-term weathering, mountain soil is dark brown, with fine and loose particles, contains organic matter, and has good drainage and air permeability; it is most suitable for cultivating pine and cypress tree species.
③ Leaf mold soil. Generally, leaves and grasses are buried in soil, and after rotting they become leaf mold soil, which contains nitrogen fertilizer; the soil is loose and fertile, and it should be mixed with sand and field soil when used.
④ Red mud. Red mud is red or dark red; the amount of sandy material in the original soil depends on the stickiness of the red mud. But regardless of the degree of stickiness, it can be used to cultivate potted trees, but it must be mixed with sand, mountain soil, or leaf mold soil before use.
⑤ Sand. There are three types of sand: sea sand, river sand, and mountain sand. Sea sand is not suitable for cultivating plants because it contains salt. River sand and mountain sand can be used in combination with sticky soil, or spread under other soils as a bottom layer to facilitate drainage; they can also be placed in sand boxes for use as cuttings medium, but sand cannot be used alone to cultivate potted trees.
⑥ Potting mix. In cities, it is generally rather difficult to obtain soil, and buying flower soil from flower shops costs relatively more; to save expenses, you can make your own potting mix. The manufacturing method is simple: you can use the old potting soil removed during repotting, mix it with chicken manure, crushed bones, garbage, plant ash, and thoroughly burned coal cinder, dry it in the sun, then add human excrement and urine, and after repeated turning, mixing, and drying, store it in jars or boxes for use at any time. This kind of potting mix is not only loose with good drainage and air permeability, but also has notable fertilizer efficiency.
⑦ Clay. Clay has a large water-holding capacity; the size of its water-holding capacity depends on the number of extremely small soil particles per unit of soil. Small soil particles can retain soil moisture better than large soil particles. However, clay has poor water permeability and air permeability and is not suitable for use alone; it is suitable for use after mixing with sand and applying organic fertilizer.
⑧ Sandy soil. Sandy soil has relatively large soil particles and better aeration and water permeability, so water and fertilizer are easily lost from sandy soil, and the upper soil layer also dries out easily; therefore, sandy soil must be improved by changing its structure and fertility to benefit plant growth.
(6) Water
Water is an indispensable factor for plant growth. The bodies of all plants contain water; all metabolic processes of plants can proceed normally only when water is present; at the same time, water is also a necessary raw material for photosynthesis in green plants. Therefore, water determines the life activities of plants. The water needed for the life of most plants is mainly absorbed by the roots. Potted plants grow in pots of limited capacity and mainly rely on watering to maintain the water in the pot soil. Therefore, watering has become a very important management task.
For watering, first understand the water quality. There are many sources of water; rainwater, river water, well water, pond water, and tap water can all be used, but water containing salt and turbid water should not be used. Second, pay attention to water temperature. In order to reduce the stimulation of water on potted trees, attention must be paid to controlling the water temperature. In summer, the air temperature is relatively high; if potted trees are watered with water whose temperature is too low, the absorptive capacity of the roots of the potted trees will be weakened, and the upper branches and leaves will shrink due to insufficient water supply. Therefore, at the maintenance site it is best to first store water in a water tank or reservoir and let the sun shine on it, in order to raise the water temperature accordingly. In cold regions, in winter water should be stored indoors for one or two days, and used only after the water temperature rises to a level not too different from the air temperature; this will not damage the roots of potted trees. Third, grasp the amount of water. In long-term practice, the author has made observations and comparisons: the same kind of plant grown in soil with sufficient water and in dry soil shows changes in its morphology and the size of its branches and leaves. The leaves of plants growing in moist soil are usually relatively large, while the leaves of plants growing in dry soil are generally relatively small. As far as stump bonsai are concerned, if the pot soil is too dry, it will cause fine roots to dry up, and afterward even watering will not allow absorption; the root system will begin to rot, the leaves will also become yellow and withered, and gradually the whole plant will die. If the pot soil is too wet and the soil contains too much water, there will be little air, the respiration of the root system will be hindered, causing suffocation, and the root system will rot and die. Based on the above circumstances, for different plant species, according to the age of the tree, the strength of growth, and different seasons, temperatures, soil qualities, and the texture and size of the pot, the frequency and amount of watering should vary.
No matter what the season, watering potted trees should achieve “water thoroughly when dry”; never give “half water.” Half water means that only the upper layer of the pot soil absorbs it and it does not seep into the lower layer of the soil, so the top is moist while the interior of the soil is dry; the root system cannot absorb water and will die. Therefore, when watering, special attention must be paid to watering thoroughly.
(1) Principles of Watering
① Water according to the season. After the Beginning of Spring, the temperature gradually warms, potted trees enter the season of vigorous growth, and the amount of watering should increase accordingly. In summer, the weather is hot, potted trees grow rapidly, water evaporation is relatively large, and the pot soil dries easily, so the amount of watering should also increase accordingly. After the Beginning of Autumn, the weather turns cooler, potted trees gradually slow down or basically stop growing, and their consumption of water is not much, so water less or water every other day. In winter, if watering is needed, it must be done during the warm daytime hours, and the amount of watering should be such that by dusk the pot soil is slightly dry.
② Water according to the weather. When the temperature is high or the climate is dry, because water evaporates quickly, water in time. When the temperature is low or the weather is cloudy and rainy, water evaporates more slowly, and the plants do not need much water, so water less or do not water.
③ Water according to the growth status and habits of the plants. When tree stumps are sprouting, water should not be excessive; this can control the growth of young shoots, because too much water may cause young shoots to grow excessively or rot. When potted trees enter the stage of vigorous growth, more watering is appropriate. During flowering, however, attention should be paid to reducing water to prevent flower drop. Plants have different habits and therefore different water requirements. A simple way to distinguish them is to judge by the size of the plant's leaves: plants with small leaves do not like water, because small leaves evaporate less water and therefore need less water. Plants with large leaves mostly like water, so they need more water. Grasping these characteristics when watering will ensure plant growth.
④ Water according to soil quality. Sandy soil has good drainage; when plants are planted in this kind of soil, they need more water, so watering should be frequent. Clay and leaf mold soil can store relatively more water, so appropriate watering is enough.
⑤ Water according to the texture, size, and depth of the pot. When watering, the decision must be based on the texture, size, and depth of the pot. Earthen pots are breathable and have good water permeability, and the pot soil dries easily; glazed pots, stone pots, and ceramic pots are not very breathable, and the pot soil dries less easily; porcelain pots are not breathable and do not permeate water, and the pot soil does not dry easily. Because pots differ in size and depth, the degree of dryness and wetness of the soil in the pot also differs; generally, the pot soil in small pots dries faster than in large pots, and the pot soil in shallow pots dries faster than in deep pots. Watering should be differentiated according to the above circumstances.
⑥ Do not cut off water. There is little soil in the pot, and the water stored is limited; after wind and sun, the pot soil dries very easily. In high-temperature seasons, of course, water frequently; on crisp autumn days, watering must not be neglected either. Even for potted trees that shed leaves and are dormant in winter, the pot soil must not be allowed to become too dry, and relative humidity should be maintained. Especially for potted trees that like water, water must never be cut off at any time.
⑦ Control water. In order to maintain the beautiful posture of potted trees that have already been trained and properly pruned, when displaying them for viewing (especially indoors), avoid watering too frequently; it is better to err on the dry side than the wet side, so as to avoid excessive growth of branches and leaves and difficulty in root respiration, which would affect the growth and beauty of the potted trees.
(2) Methods of Watering
① Spraying water. For newly planted tree stumps or potted trees after soil replacement, the roots are more or less damaged and water absorption is relatively difficult; a fine-hole watering can may be used to spray water, so that the water flow is small and even and will not disturb the pot soil and affect water absorption by the roots.
The first spraying should apply enough water to soak through to the bottom of the pot; afterward, the trunk, branches, and leaves should also be sprayed frequently, and the pot soil should be kept moist. As for large areas, a hose may be used for spraying according to actual conditions.
② Sprinkling water. Trees such as azaleas and pines and cypresses that naturally grow in high mountain clouds and mist are accustomed to absorbing moisture in the forest. Once transplanted into pots and their environment changed, their growth will be affected to a certain extent. In order to adapt to their growth habits, water must often be applied to the leaves. This can not only wash away dust accumulated on branches and leaves and keep the potted trees beautiful in color, but also clear the stomata on the leaf surface and promote plant metabolism.
However, for some potted trees, if the leaves are watered too much, their branches and leaves will instead grow excessively; for example, orange jasmine, pomegranate, and elm are all unsuitable for sprinkling water on the leaves.
③ Soaking water. For potted trees planted in shallow pots and miniature bonsai, the pot soil is shallow and little; when exposed to the scorching sun, the pot soil hardens, turns white, and shrinks, developing cracks, and some becomes blocky and separates from the pot. At this time, when watering, the water often quickly flows from around the pot to the bottom and drains out through the drainage hole. In this situation, the potted tree should be placed in a larger basin filled with water so that the potted tree can absorb water thoroughly, until no more bubbles emerge from the water surface, and then it can be lifted out.
(7) Fertilization
The pots of stump bonsai are small in volume, and the nutrients in the pot soil are limited; sufficient nutrients must be provided in time for them to grow well and develop normally. Potted trees continuously absorb various nutrients during growth, so fertilization must be frequent, but too much fertilizer at one time is not appropriate; applying too much fertilizer causes excessive growth of branches and leaves, affecting the beauty of the potted tree's posture and hindering appreciation; while lack of fertilizer means insufficient nutrients, causing tree branches to become thin and weak, leaf color to turn yellow, development to be inhibited, and susceptibility to pests and diseases, resulting in the death of the potted tree. Therefore, basic knowledge such as fertilizer types, functions, preparation methods, fertilization principles, and methods must be mastered. In short, it must be used flexibly according to time, place, fertilizer, and tree species in order to achieve the purpose of fertilization.
(1) Types and Functions of Fertilizers
There are many types of fertilizers, but those used for stump bonsai are nothing more than two major categories: inorganic fertilizers and organic fertilizers.
Inorganic fertilizers refer to chemical fertilizers, also called mineral fertilizers; they are manufactured by the chemical industry, such as ammonium sulfate, ammonium nitrate, ammonium chloride, and urea as nitrogen fertilizers; superphosphate, phosphate rock powder, etc. as phosphate fertilizers; and potassium sulfate, potassium chloride, etc. as potassium fertilizers. After the nutrients of chemical fertilizers are absorbed by plants, acid radicals or base salts will remain. After excessive use of chemical fertilizers, the limited pot soil will become acidic or alkaline, hindering plant growth. Therefore, stump bonsai should avoid the application of chemical fertilizers as much as possible.
Organic fertilizers are also called farmyard fertilizers. Commonly used ones include human excrement and urine, poultry manure, bone meal, as well as soybean cake, rapeseed cake, various green manures, and plant ash; these fertilizers contain large amounts of organic matter and respectively contain nitrogen, phosphorus, and potassium elements in different compositions. Organic fertilizers play a major role in improving soil properties and increasing soil fertility; organic fertilizers have a mild fertilizer effect and no side effects after application, and are indispensable nutrients for plant growth.
The functions of various fertilizers are different. Nitrogen fertilizer promotes luxuriant branches and leaves; phosphorus fertilizer promotes seed germination, growth, and the formation of flowers and fruits; potassium fertilizer promotes strong, tough stems and branches that are not easy to lodge, as well as developed roots and absorption, thereby enhancing the potted tree's ability to resist cold, drought, pests, and diseases.
After mastering the types and functions of fertilizers, they can be applied according to different needs such as foliage appreciation, flower appreciation, and fruit appreciation.
(2) Common Fertilizer Preparation Methods
① Composting human and livestock excrement and urine. Human and livestock excrement and urine have wide sources and relatively notable fertilizer efficiency, and are commonly used by people. However, fresh, thick human and livestock excrement and urine that has not been stored and not fully decomposed should not be used, because it is not easily absorbed by plants and can damage plant roots. Therefore, human and livestock excrement and urine must be stored in jars, covered and sealed at the mouth, and kept in a cool place; only after ten days to one month of decomposition can it be applied. When applying, it should be diluted with several times or several dozen times clean water; if the manure water is applied to the leaves, it must be immediately rinsed with clean water to avoid burning the leaves.
② Soaking crushed soybean cake, peanut cake, rapeseed cake, and animal bone fragments. Place the above crushed fertilizers into a jar, add about ten times water to soak, cover and seal the jar mouth to prevent rainwater from entering, and store for about twenty to thirty days. When applying, dilute with clean water twenty to thirty times.
③ Bone meal treatment. After animal bones are steamed, the fat is removed, and then after drying and grinding they become bone meal. The phosphorus in bone meal exists in the form of sparingly soluble tricalcium phosphate; it is suitable as a base fertilizer and is suitable for acidic soil.
(3) Fertilization Methods
① Base fertilizer. Fertilizer applied to the soil before sowing, transplanting, planting, or changing soil is called base fertilizer. The main function of base fertilizer is to supply the nutrients needed for the entire growth and development of the crop and to comprehensively improve soil properties. Base fertilizer is mostly organic fertilizer; the application method is to place powdered or granular peanut cake, soybean cake, rapeseed cake, cottonseed cake fertilizer, or bone meal, etc., at the bottom layer or around the sides of the pot, allowing them to slowly decompose and be absorbed. But be careful not to apply excessively, otherwise it will burn the root system and seedlings. Base fertilizer alone is far from enough to meet the long-term growth needs of potted trees; this will cause incomplete development of the potted tree and gradual weakening. Therefore, base fertilizer and topdressing must be organically combined.
② Topdressing. Fertilizer applied during the plant's growth period is called topdressing. Topdressing mostly uses dilute liquid fertilizer. The principle of frequent and light application should be grasped when applying topdressing. Under normal circumstances, potted trees are fertilized once every seven days; after autumn, this can be extended to about once every twenty days. When applying, distinguish tree species and their different growth stages: after sprouting and rooting, mainly apply nitrogen fertilizer to promote the development and luxuriance of branches and leaves; before flowering or during the fruiting stage, mainly apply phosphorus and potassium fertilizer, while also applying an appropriate amount of nitrogen fertilizer; after flowering and fruiting, quickly restore the vigor of the potted tree, and be sure to topdress once every fifteen days or so until it can stop only after autumn.
(4) Fertilization Principles
① Fertilize according to the needs of the potted tree's growth period. Fertilization must be based on the growth and development needs of the potted tree at each different stage. Newly planted, newly potted, or just repotted potted trees have roots damaged to a certain extent; for safety, do not fertilize them for the time being, and later topdress as appropriate according to the growth of the potted tree. During the vegetative growth period of the potted tree, nitrogen fertilizer should be applied to make branches and leaves luxuriant; to promote seed germination, growth of young roots and buds, and fresh flower and leaf color and plump fruit, phosphorus fertilizer can be applied; to strengthen the root system, trunk, and branches, potassium fertilizer is suitable. Fertilizer can also be applied when the leaf color of the potted tree becomes pale or yellow or the plant is thin and weak.
② Fertilize according to season and weather. Fertilization should be based on the season. Spring and summer are the peak growing seasons for potted trees, so more fertilizer must be applied. After autumn, potted trees grow slowly, so fertilize less. In winter, potted trees enter dormancy, so fertilization can be paused or a little potassium fertilizer applied.
Fertilization should also take weather into account. It is not suitable to fertilize on rainy days or around noon during high summer temperatures. Because fertilizing on rainy days makes nutrients easily lost; fertilizing in high-temperature weather easily affects the root system of potted trees. Therefore, it is best to fertilize on cloudy days or in the evening after the pot soil has dried, for better results.
(5) Points to Note
① Weed and loosen the soil before fertilizing. During the growth of potted trees, many weeds also grow and compete with the potted trees for nutrients. The surface of the pot soil may also become compacted. Therefore, before fertilizing, first remove the weeds, then loosen the soil with a bamboo stick; this not only helps fertilizer water penetrate into the soil and benefits the reproduction of microorganisms, but also promotes the accelerated decomposition of organic fertilizers in the soil, providing plants with various elements and enabling good plant growth.
② Water after fertilizing. Potted trees should be watered more after fertilizing; otherwise, with much fertilizer and little water, the fertilizer will generate high temperatures after fermentation and burn the root system. In severe cases, it can lead to death. Therefore, after fertilizing potted trees, clean water must be applied the next morning, commonly called “return water”; this not only helps the absorption of nutrients but also avoids fertilizer damage.
③ Grasp the fertilization site. No matter which liquid fertilizer is applied, never apply it to the young buds and new leaves of potted trees to prevent burning.
(8) Pruning
During the cultivation process and after being trained and potted, stump bonsai should undergo necessary pruning and shaping. If not pruned for a long time and allowed to grow freely, even potted trees that were originally shaped will develop a tangle of miscellaneous branches, chaotic and disorderly, so that the stump bonsai can no longer develop in a balanced way, affecting the beautiful tree shape; moreover, poor ventilation and light can cause some branches and leaves to wither, fall off, and produce pests and diseases. Therefore, regular pruning of stump bonsai is, on the one hand, to maintain the basic form of the potted tree and even growth of all parts, and on the other hand, to cut off excessively dense branches and leaves that hinder ventilation and light, regulate tree vigor, make the stump grow vigorously, and allow old branches to be renewed. Only in this way can the goals be achieved of being beneficial for viewing and also preventing pest and disease damage, enabling healthy growth of the potted tree.
In pruning methods, leaves should first be thinned. Look clearly at the whole tree before starting; once cut incorrectly, the tree shape will be ruined. At the same time, different methods such as branch pruning, pinching, bud removal, and leaf removal should be used according to differences in tree species, growth vigor, and season.
① Branch pruning. After potted trees have taken shape, they still continue to grow; especially in spring and summer, branch tips grow rapidly and densely, and the tree shape is not easy to maintain. In order to control the original form of the potted tree and highlight the trunk and main branches, branch pruning must be carried out. Branch pruning can be done during dormancy and growth periods. But the number of prunings should vary according to the different habits of tree species and different seasons. For foliage-viewing stump bonsai, such as pines and cypresses, pruning can be carried out three times each year in March, June, and August respectively; for elm, Japanese bush cherry, Fujian tea, orange jasmine, and Mantianxing, which have strong sprouting ability, generally prune three to five times each year, and it can be done in spring, summer, and autumn.
Generally speaking, branch pruning should follow the following principles: First, potted trees with strong and vigorous growth can be pruned in all four seasons. In order to ensure the vegetative growth of the potted tree, for weak-growing potted trees, do not prune much or do not prune, and prune only after they become vigorous. Second, in high summer temperatures, prune appropriately less or temporarily do not prune. Of course, dead branches and pest- and disease-infected branches of potted trees must be cut off and burned at any time to avoid affecting tree growth. Third, first cut off water sprouts, radiating branches, crossing branches, overlapping branches, and straight branches. Fourth, the thinning and retention of branches should be determined according to the characteristics, layout, and requirements of the potted tree; branches, spurs, and leaves that hinder viewing should be thinned and pruned so that they interweave and set each other off, with proper density.
② Pinching. In order to keep the crown form unchanged or increase the number of flowers of flowering potted trees, pinching can be carried out. Pinching means removing the terminal buds of certain branch tips to inhibit branch elongation and promote branching growth. The specific method is to promptly remove unnecessary terminal buds and retain terminal buds in good positions. For areas where branches are too sparse, top and pinch to promote more lateral branches and make the plant form fuller. Pinching should differ according to tree species; for example, Buddhist pine grows several times a year, so pinching must also be carried out several times.
③ Bud removal. After pruning or repotting, potted trees will grow many axillary buds on the trunk and branch spurs. If not attended to and allowed to grow, they will not only destroy the original form of the potted tree but also disperse nutrients, which is unfavorable for growth; at the same time, too many branches also hinder air circulation and sunlight exposure, making pests and diseases likely. Therefore, according to shaping needs, all young buds not to be retained must be removed or cut off. For pines and cypresses, the main buds at the branch tips should be removed in spring to promote the second flush of pine needles to be shorter and more aged, making them natural and beautiful. For example, branches grown last year, if too long, can also be slightly shortened; afterward they will also sprout and grow branches from the needle bundles. However, cutting the young branches of pines and cypresses with scissors will make the wounds turn rusty in color, so it is best to remove them by hand. For tree species such as elm, Japanese bush cherry, Fujian tea, and orange jasmine, which have strong sprouting ability and sprout very easily, attention must be paid to bud removal at all times.
④ Leaf removal. The best viewing period for potted trees is when new leaves have just grown, because at this time the leaves are small, the color is beautiful, fresh and lush, full of vitality. Leaf removal is an effective measure for shaping deciduous trees. Because leaf removal can change a potted tree from sprouting new buds once a year to sprouting twice a year, forming extremely beautiful, fine, and dense branches and prolonging the viewing period. For many tree species such as elm, pomegranate, ginkgo, Chinese hackberry, and small-leaved banyan, all leaves can be removed, and in about twenty days new buds will grow again on the branches. For potted trees to be defoliated, fertilizer should be applied before leaf removal, and they should be placed in a place with ample sunlight to promote vigorous growth of the potted tree and improve the regenerative capacity of the leaves.
(9) Repotting
Repotting of stump bonsai usually refers to changing the potted tree into new soil; some also call it “repotting and replanting” or “repotting,” “changing pots.” Why must stump bonsai be repotted? There are two reasons: one is that the condition of the soil changes. The other is that the root system of the potted tree changes.
Potted trees grow in limited pot soil; after two or three years, the root system gradually grows, the nutrients in the pot soil are absorbed completely by the plants; with year after year of watering, the soil decreases, and the soil in the pot becomes compacted, resulting in poor drainage and aeration.
For relatively thick and large stump bonsai cultivated for many years, after a relatively long period of growth, old roots are densely packed and squeeze each other, making it difficult for new roots to grow and hindering the growth of the potted tree; a larger pot must be used with new soil to increase soil nutrients.
In short, the purpose of repotting is to ensure the normal growth and development of the potted tree.
(1) Repotting Season
Repotting is usually carried out during the period when trees are dormant or developing slowly. Most trees are repotted in spring and autumn. In spring, it is usually from late February to early May; in autumn, it is best from late October to mid-November. But different tree species have different requirements. For example, elm is cold-tolerant, and the best time for repotting is near the Beginning of Spring; while Fujian tea, orange jasmine, and Japanese bush cherry share the characteristic of liking warmth and fearing cold, so repotting should be carried out near the Summer Solstice; although pines like sunlight and are not afraid of cold, they dislike dampness, so repotting is safest around mid-April, because by then the plum rain season is basically over and the weather is not too hot; azaleas have strong growth ability, and apart from the hot summer and winter, they can be repotted at any time, but they should be repotted only after flowering.
As for the service life of pot soil, it should be determined according to tree growth vigor and the condition of the pot soil. For vigorous-growing ones whose pot soil still has good drainage and aeration, repotting can be temporarily omitted; for flower-viewing and fruit-viewing bonsai, which consume more nutrients, generally repot once every one to two years; for small-leaved evergreen plants and trees in large pots, because they consume fewer nutrients, repot once every two to three years; for miniature bonsai, because the pot is small and the soil is little, repot once a year.
(2) Repotting Methods
As said above, repotting of stump bonsai usually means changing the soil rather than the pot. Before repotting, first prepare the potting mix. Because different potted trees have different soil requirements, before repotting be sure to select and mix an appropriate potting mix according to the growth characteristics of the potted tree, and then begin.
① Wash the pot. When an old or originally used pot is reused, it must be washed clean with clean water and then dried in the sun; this can have a disinfecting and sterilizing effect. If it is a newly bought pot, it must be soaked in water for a period of time before use, which both cleans it and removes “fire heat.”
② Cover the drainage hole. The drainage hole at the bottom of the pot should be covered with a curved tile piece; this not only prevents a large amount of pot soil from being lost but also facilitates water permeability. If it is a tall or deep pot, in addition to covering with a curved tile piece and leaving more gaps, the lower layer can also be spread with a layer of coal cinder; the coal cinder particles should be coarser to facilitate drainage.
③ Handle old soil. Turn the tree out of the pot together with the soil, and use a bamboo stick to remove old soil mixed in among the root system of the potted tree. How much old soil to remove should vary according to tree species. For example, for pines, about half of the old soil can be removed, and then new potting mix added for planting; for elm, pomegranate, azalea, and other tree species with many fine roots and easy growth, all old soil can be removed and new potting mix added for planting.
④ Handle the root system. For potted trees cultivated for one or two years and turned out of the pot, fine roots cover the pot soil; use a bamboo stick to slowly remove part of the old soil, cut off all decayed old roots, and at the same time cut off part of the straight roots and newly grown fine roots; there is no need to keep too many or too long, so as to avoid reducing the amount of soil the pot can hold. For example, for the elongated fine roots of pines, two-thirds should be cut off. However, for those with poor root development, the old roots may not be removed, in order to stabilize the base.
⑤ Plant according to the composition. Generally, tree stumps can rarely be viewed from two sides; most have one better side and one inferior side, so the viewing side must be determined before planting. Whether the planting position of a stump bonsai is appropriate or not directly affects the layout and artistic effect of the stump bonsai. Whether tall cylindrical, square, round pots, or various tree forms, from an artistic point of view, it is always inappropriate to plant the stump in the center of the pot. Therefore, when planting, the whole tree and the pot must be laid out as a unified whole, with relative echo and coordination, striving to achieve the artistic conception of gathering like a crouching tiger and spreading like a roaming dragon. The ratio of tree to pot edge should generally be 3:7 or 4:6, that is, it is appropriate for the potted tree to lean slightly toward any side of the pot, left, right, front, or back. For some large tree-form potted trees with gnarled roots and ancient, vigorous character, where the artistic conception requires steadiness and dignity, planting slightly more toward the center is also acceptable.
However, for cascade-style potted trees, when planted in tall cylindrical or square pots, attention must be paid to their position and the tendency of the tree head, tree roots, and tree momentum to surge and the center of gravity of the pot shape; there should be a momentum of being dangerous but not falling, slanting but not toppling, and the trunk must not press tightly against the pot edge. As far as possible, use the corner-pressing method and the staggered-corner method. The corner-pressing method is to make the head and roots close to the pot edge; the staggered-corner method is to make the pot corner slightly face the viewing side, avoiding stiffness in the potted tree.
(10) Prevention and Control of Common Pests and Diseases
Because bonsai are often placed indoors, where light or ventilation conditions are relatively poor, various pests and diseases often occur; in mild cases the plant becomes thin and weak with few flowers and yellow leaves, and in severe cases the whole plant dies. The active control method is based on the principle of “prevent pests and diseases early when there are none, treat them early when present, give priority to prevention, and give priority to treating the root cause,” eliminating pests and diseases at the budding stage so that pests and diseases do not spread and expand.
(1) Preventive Measures
① Strengthen the maintenance and various management tasks of bonsai. Master scientific methods of fertilization, watering, and pruning; the site should be kept clean, and suitable temperature and humidity maintained, so that potted trees have ventilation and light on all sides.
② Use decomposed fertilizer and disinfect the soil. The simplest soil disinfection method is to heat the pot soil in a wok or expose it thoroughly in the hot sun to kill pathogens and insect eggs in the soil.
③ Spray preventive chemicals. In spring, various potted trees enter the season of vigorous growth; spraying potted trees with Bordeaux mixture at a concentration of one percent one to three times can prevent pests and diseases. The preparation method of Bordeaux mixture is: dissolve one jin of copper sulfate and one to two jin of quicklime separately in one hundred jin of water, then pour them at the same time into a third container and stir evenly.
④ Eliminate sources of infection. For all tree stumps dug up or bought from elsewhere, carefully check whether there are pests or diseases. If pests or diseases are found, quickly take effective control measures. If some potted trees show pests or diseases, immediately isolate them to prevent spread. For individual cases that are especially severely damaged and difficult to manage, burn or bury them deeply as early as possible, avoiding a small loss causing a great loss.
(2) Common Diseases and Their Control Methods
Stump diseases are generally divided into two major categories: physiological diseases and parasitic diseases.
Physiological diseases are caused by abiotic factors. For example, unsuitable temperature, humidity, soil, or fertilizer, or a deficiency of trace elements and other environmental factors, can cause physiological disorders and lead to disease.
Parasitic diseases are caused by biological factors. For example, fungi, bacteria, viruses, nematodes, and other organisms parasitize within ornamental plants and cause various kinds of disease, among which fungal diseases are the most numerous.
Several common diseases and their control methods are described below.
(1) Powdery mildew. On the leaves, branches, flower stalks, and flower buds of affected plants, a layer of white powdery material grows on the surface. Affected plants are short and not luxuriant, the leaves are uneven or curled, the branches develop abnormally, and the flower buds are destroyed, so the plant cannot bloom or produces deformed flowers. In severe cases, the flowers are few and small, and the leaves shrivel and dry up, seriously affecting plant growth and even causing the whole plant to die. The disease is mostly caused by overly wet potting soil, excessive nitrogen fertilizer, and too long a period in shade.
Control method: Attention should be paid to ventilation and sunlight, humidity should be controlled, and diseased leaves should be cut off and burned together; also, when the morning dew has not yet dried, spray a small amount of sulfur powder or 0.2 to 0.3 degree lime sulfur mixture, which can achieve a controlling effect.
(2) Root rot. This disease often occurs after stump heads dug from the wild are planted in pots. Most cases are caused by poor transplanting, together with wounds being invaded by pathogens, plus excessive watering, waterlogged soil, and poor aeration, which suffocates the root system and causes rot. Excessive fertilization can also cause root rot. After the roots rot, their absorption function is hindered, leading to withered branches and fallen leaves on the aboveground part.
Control method: Carefully dig up the original plant, prune the rotted parts of the root system, then replant it with new soil, and change the growing conditions of the bonsai by increasing light, loosening the soil, and properly controlling fertilizer and water to promote its recovery.
(3) Leaf mold. In the early stage of the disease, round purplish-brown spots appear on the leaves and enlarge day by day, with the center becoming pale yellowish-brown and the edges purplish-brown, and the spots have obvious concentric rings. By autumn, the spots turn dark brown, become scorched and brittle, and break easily, with dark green mold-like growth on them. In severe cases, the spots often spread from the lower leaves of the plant to the leaves of the whole plant, causing a large number of scorched leaves and affecting growth and flowering the following year. The disease is mostly caused by poor management; for example, it occurs frequently when humidity is high or after the plants have been frozen.
Control method: Mainly strengthen management, pay attention to pruning, keep the plants ventilated and exposed to light, and keep the soil dry and refreshing. Timely clean up diseased leaves and diseased dead branches and burn them. You can also prevent it in early spring and early autumn by spraying once a week with 120 to 160 times diluted equal-amount Bordeaux mixture or 500 to 600 times diluted 65% zineb wettable powder.
(3) Common insect pests and their control methods
(1) Slug moths. From June to October each year, slug moths feed heavily on the leaves of potted trees, and in severe cases can eat the leaves completely, causing the trees to wither and die. The vast majority of slug moths have two generations a year and overwinter as mature larvae in cocoons.
Control method: First, remove the overwintering cocoons, cut off young larvae and egg masses, or set up lights at night to trap and kill them. Second, when the larvae are abundant, spray with 90% trichlorfon 1,000 times diluted solution, or spray a mixture with 6% wettable benzene hexachloride 200 times diluted solution added.
(2) Bagworms. Bagworms are commonly called "bag worms" or "raincoat worms." From June to October each year, they gnaw the leaves and branch tips of potted trees. They can live in harsh environments such as hunger and drought. Especially the nearly mature larvae often hide for several days without eating and will not die.
Control method: The same as for slug moths, but because they are wrapped in a shell, spraying chemicals is hard to make effective. If there are few, it is best to catch them by hand.
(3) Longhorn beetles. Longhorn beetles have one generation every one to two years and overwinter as larvae in the tree trunk. Newly hatched larvae gnaw in a winding manner under the bark, then bore into the trunk and roots, and then pupate inside. Adults begin to emerge in late May and feed on branch tips and tender leaves. Affected potted trees often end up dying.
Control method: Catch and kill adults and crush eggs. For those that have bored into the wood, you can use a steel wire to hook them to death; or soak a cotton ball in dichlorvos and plug it into the bore hole, then seal the opening with yellow mud; or use dimethoate diluted with water 5 to 10 times and drop it into the bore hole to poison the larvae. You can also cut off the damaged branches and immediately burn or deeply bury them.
(4) Scale insects. Common ones include the cottony cushion scale and armored scales. The cottony cushion scale has white waxy filamentous hairs; armored scales are shield-shaped and brown. Scale insects mainly suck the sap of the branches and leaves of potted trees, causing poor growth and even death of the whole plant. The secretions excreted by scale insects clog the stomata on the leaf surface and often cause sooty mold.
Control method: In the early stage of larval hatching, spray with dichlorvos 800 to 1,500 times diluted solution, or use a brush dipped in water to brush the insects off the potted trees and kill them. In addition, properly prune the branches so that the branches and leaves are ventilated and exposed to light.
(5) Aphids. Aphids are small and may be green, brown, red, black, gray, and so on. Their reproductive capacity is very strong, reaching 10 to 30 generations a year, and the period from about March to October each year is their breeding season. These insects gather on the young tender branches and leaves of trees, suck nutrients, cause the tender shoots to shrivel, the tender leaves to curl, and tumor-like protrusions to form, and attract ants, spreading other diseases.
Control method: Spray with dimethoate emulsifiable concentrate 1,000 to 2,000 times diluted solution or dichlorvos 1,500 to 2,000 times diluted solution. However, elm, hackberry, pomegranate, and others are sensitive to dimethoate and will drop their leaves after spraying, so instead use rotenone 1,000 times diluted solution or another pesticide for spraying.
(6) Red spider mites. Red spider mites are small and often red. In high-temperature and dry environments, they reproduce especially quickly, with 7 to 14 generations per year, and almost all potted trees suffer from them. They like to spin webs on plants and suck sap under the webs; affected leaves turn yellow and fall, affecting the tree's vigor, and some even cause the whole plant to die.
Control method: Spray with dimethoate or dichlorvos 1,500 to 2,000 times diluted solution, and at the same time pay attention to increasing air humidity.
(7) Snails. Snails mainly bite off tender branches, affecting plant growth.
Control method: Snails like moisture, so catch and kill them in the early morning or on rainy days. On sunny days, scatter some lime powder around the pot, which can also achieve a certain control effect.
(8) Ants. Ants damage young buds and sometimes build nests in the potting soil, harming fine roots.
Control method: Usually scatter some lime powder at the base of the pot, or spray diluted insecticide. If there are nests in the potting soil, you can repeatedly lure the ants out with sugar and kill them with fire or scalding water; you can also place the potted tree in water for a period of time to drown or drive away the ants. You can also pour a small amount of diluted dichlorvos solution into the soil to kill them. If none of the above methods can completely eradicate them, then you have no choice but to pull up the potted tree, remove the original old soil and roots, disinfect the pot, and replant it with new soil, with strengthened management afterward.
(9) Underground pests. The main one is the cutworm, which has four generations a year, overwinters as pupae or mature larvae in the soil, and adults emerge in mid-March. Both adult moths and larvae eat the tender stems and leaves of flower and tree seedlings, causing potted trees to die.
Control method: When changing the soil and repotting, eliminate eggs and larvae, and spray with tea seed cake water 6 to 10 times diluted solution or 15% malathion 800 times diluted solution.
(4) Commonly used pesticides and their application rates
(1) Trichlorfon. Trichlorfon is a highly effective and low-toxicity insecticide, with relatively low toxicity to humans and livestock, and it is not easily absorbed through the skin. Trichlorfon has strong stomach poison and contact-killing effects, and is most effective against pests of Diptera, Hymenoptera, Coleoptera, and others. It can be used to control caterpillars, leaf rollers, slug moths, and many other pests with very good results, but it is less effective against pests such as aphids and red spider mites.
Trichlorfon formulations include 2.2% powder and 50% and 80% soluble powders. The concentration generally used for trichlorfon is about 0.1%, and the diluted solution should be prepared and used immediately.
(2) Dichlorvos. Dichlorvos is a highly effective and highly toxic insecticide, with medium toxicity to humans and livestock. It has fumigant, stomach poison, and contact-killing effects on pests, and has good control effects on both chewing-mouthpart pests and piercing-sucking mouthpart pests. Dichlorvos is highly volatile, with relatively high vapor pressure, and has a strong knockdown effect on pests. After application, dichlorvos decomposes easily and has a short residual period.
Dichlorvos formulations include 50% emulsifiable concentrate, 80% emulsifiable concentrate, and 60% dichlorvos plus 20% dimethoate mixed emulsifiable concentrate.
The application rate is to mix 50% emulsifiable concentrate with clean water to make a 1,000 to 1,500 times diluted solution, or 80% emulsifiable concentrate to make a 2,000 to 3,000 times diluted solution, or 60% dichlorvos plus 20% dimethoate mixed emulsifiable concentrate to make a 2,000 to 3,000 times diluted solution for spraying, which can effectively control aphids, red spider mites, leafhoppers, leaf rollers, and other pests. You can also mix 80% emulsifiable concentrate with water to make a 1,000 times diluted solution for spraying, which can control various slug moths, scale insects, and others.
Dichlorvos emulsifiable concentrate volatilizes easily, so the solution should be prepared and used immediately, but the dosage must be strictly controlled and the concentration should not be too high, so as to avoid phytotoxicity.
(3) Dimethoate. Dimethoate is a highly effective and low-toxicity insecticide with relatively high contact-killing efficacy and also systemic activity. In particular, its toxicity to pests increases markedly as the temperature rises, so the spraying concentration should be determined according to the temperature. When used, it can generally be mixed with ordinary insecticides and fungicides, but must not be mixed with alkaline pesticides. Dimethoate is suitable for controlling many pests, and has very good control effects on common pests of potted trees, such as slug moths, aphids, red spider mites, and many piercing-sucking mouthpart and chewing mouthpart pests.
Dimethoate formulations include 20% emulsifiable concentrate, 40% emulsifiable concentrate, 60% soluble powder, 1.5% crystalline technical powder, and 2% crystalline technical powder.
Mix 40% dimethoate emulsifiable concentrate with clean water to make a 1,000 to 1,500 times diluted solution, or 60% soluble powder with water to make a 1,500 to 2,000 times diluted solution for spraying. The effect can last about ten days, and it is notably effective in controlling common pests.
Dimethoate is stable to sunlight, but moisture easily causes decomposition, so it decomposes slowly during storage. Among potted trees, plants such as elm, hackberry, and pomegranate are sensitive to dimethoate and are not suitable for use in pest control, otherwise early leaf drop will be caused.
(4) Fenitrothion (sumithion). Fenitrothion has a broad insecticidal range and strong contact-killing and stomach-poison effects on piercing-sucking mouthpart, chewing mouthpart, and boring pests. It has no systemic action, but has good permeability in plant tissues, and has relatively low toxicity to humans and livestock.
Fenitrothion formulations include 2% powder and 50% emulsifiable concentrate.
Mix 50% emulsifiable concentrate with clean water to prepare a 1,000 to 1,500 times diluted solution for spraying, which can effectively control slug moths, red spider mites, caterpillars, and many kinds of scale insects.
But note that it must not be mixed with strongly alkaline pesticides. If it needs to be mixed with Bordeaux mixture, it should be mixed temporarily just before application.
(5) Phosmet. Phosmet is an insecticide with low toxicity to humans and livestock, has a broad insecticidal range, acts mainly by contact-killing, and has a short residual period.
Phosmet formulations include 2.5% powder, 25% wettable powder, and 25% emulsifiable concentrate.
Mix 25% emulsifiable concentrate or 25% wettable powder with clean water to prepare a 1,000 times diluted solution for spraying, which can control red spider mites, aphids, and others; use an 800 to 1,000 times diluted solution to control pests such as slug moths; use a 400 to 600 times diluted solution to control scale insects and many other pests.
Phosmet can be mixed with DDT, but cannot be mixed with Bordeaux mixture. After use, hands, feet, and face must be washed to prevent effects on the human body.
The concept of aquatic plants and their applications
Aquatic plants refer to plants that grow in water or in moist soil, including herbaceous plants and woody plants. China has many water systems, and aquatic plant resources are very rich; there are more than 300 species of higher aquatic plants alone. In gardens, according to different forms and ecological habits, they can be divided into five major categories:
1. Submerged plants: Their roots are anchored in the underwater soil, and the whole plant is submerged below the water surface. Common ones include tape grass, large water celery, Potamogeton crispus, Hydrilla verticillata, water hyssop, Potamogeton malaianus, Myriophyllum, Ottelia alismoides, Limnophila sessiliflora, Blyxa, and Cabomba.
2. Floating plants: Their stems and leaves or thalli float on the water surface, and their root systems hang suspended in the water and drift freely. Common ones include water hyacinth, duckweed, Nuphar, and water hyacinth.
3. Floating-leaved plants: Their roots grow in the underwater soil, their leaf stalks are slender, and their leaves float naturally on the water surface. Common ones include Nymphoides, water lilies, Azolla, and water chestnut.
4. Emergent plants: Their stems and leaves extend above the water surface, and their roots and underground stems are buried in the mud. Common ones include yellow flag iris, Scirpus, cattail, Acorus calamus, bulrush, reed, lotus, Alisma, Monochoria, 1 species of Hygrophila, and Scutellaria barbata.
5. Waterside plants: Their root systems are often anchored in moist soil, are tolerant of water and moisture, and can endure being submerged for a short time. Common ones include weeping willow, dawn redwood, pond cypress, bald cypress, bamboos, Chinese swamp cypress, purple loosestrife, water pepper, and cotton rose.
II. Functions of aquatic plants
1. Biodiversity function
Aquatic plant resources are very rich and varied in species, gradually transitioning from terrestrial to submerged forms, with rich layering. In addition, the plant form, leaf shape, and flower shape of aquatic plants each have their own characteristics. The formation of aquatic plant communities provides habitat for wildlife, water birds, and insects. It is precisely because of the continuous reproduction and interaction of these aquatic animals and plants that water bodies become aquatic ecological environments full of life and vitality.
2. Environmental beautification function
Aquatic plants have a landscaping function. In China's classical gardens, aquatic plants were one of the important materials for creating garden water scenery. All kinds of water bodies rely on plants to create rich and colorful water landscapes. Aquatic plants play the role of adding the finishing touch to water scenery, adorning the water surface and banks with their free and easy posture, graceful lines, and brilliant colors, and forming reflections in the water, making the water surface and water body lively and strengthening the beauty of the water body. Aquatic plants of different forms and colors evoke various psychological responses and dramatic effects in people. Broad-leaved cattails and reeds standing in the water, their reflections in sunlight or their hazy posture under thin mist, make people imagine endlessly; reeds under the moon and the moonlight over a lotus pond, poetic in their tranquility, give people a sense of mystery; while Acorus calamus, water lilies, arrowhead, water chestnut, purple loosestrife, and others bloom beautifully in competition, and their enchanting colors give people a strong visual impact. Among the famous 72 scenes of the Chengde Mountain Resort and the 40 scenes of the Old Summer Palace, most are mainly based on aquatic plant landscaping, such as the scenic spots "Qu Shui He Xiang," "Ping Xiang Ban," and "Ling He Shen Chu"; the West Lake in Hangzhou's "Su Causeway in Spring Dawn," "Orioles Singing in the Willows," "Winding Courtyard with Windblown Lotuses," and so on are all famous because of aquatic plant landscaping.
In addition, on open water surfaces, floating beds and floating islands can also be arranged, and aquatic flowers can be cultivated on the islands to form a "water garden," adding scenery to the water surface. For example, the floating islands on the water surface of Beidou River in Ningbo broke the original monotonous and dull water surface and brought vitality and energy to the water body.
3. Water purification function
Aquatic plants not only beautify the environment, but also have the function of purifying water quality. Aquatic plants can carry out photosynthesis, absorb CO2 from the environment, release O2, improve water quality, and eliminate many polluting elements in water bodies, so aquatic plants have an important ecological restoration function. According to research: Scirpus can purify phenols in water; wild arrowhead removes 75% of nitrogen and 65% of phosphorus from water bodies; reeds have the ability to purify suspended solids, chlorides, organic nitrogen, and sulfates in water, can absorb mercury and lead, and remove 65% of phosphorus from water bodies; water hyacinth, also known as water hyacinth, reproduces quickly and has strong pollution resistance, and can absorb nitrogen, phosphorus, potassium, and heavy metal ions; submerged plants can also promote the deposition of suspended solids and pollutants in water, and can reduce nutrients in water through absorption, transformation, and accumulation, thereby inhibiting the production of planktonic algae in water bodies, while also preventing sediment from resuspending and improving water transparency. In short, when aquatic plants flourish, water quality is clear, aquatic products are abundant, and the water body ecology is stable; when aquatic plants are lacking, water quality is turbid, aquatic animals are scarce, and the water body ecological environment is fragile. Aquatic plants have significant effects in beautifying water landscapes, purifying water quality, and maintaining the ecological balance of rivers.
4. Riverbank protection and water source conservation function
By using the strong soil-penetrating and soil-stabilizing ability of plant roots, trees, shrubs, and ground cover plants tolerant of water and moisture are planted on slopes and in the fluctuation zone (the water level change zone between the highest and lowest water levels). On the one hand, this reduces surface runoff, and on the other hand, it prevents or reduces erosion and scouring of riverbanks by water flow and waves, playing a role in stabilizing soil and protecting slopes. At the same time, the growth of plant roots, stems, and leaves improves the soil, increases the content of soil organic matter, improves soil structure and properties, raises soil water-holding capacity, and increases soil erosion resistance. Therefore, planting aquatic plants along the banks can both conserve soil and water and play a role in stabilizing soil and protecting banks, and can also increase the fertility of riverbank soil and improve the ecological environment. So using plants to stabilize soil and protect banks is indeed an effective and feasible form of ecological slope protection.
5. Economic benefits
Aquatic plants are good green manure and also good forage grass. They are rich in nutrients and grow very quickly. The nitrogen and phosphorus in water are absorbed by them and converted into nutrients such as protein. According to research, every 100 grams of fresh grass contains 0.2-0.24 grams of nitrogen and 0.03-0.09 grams of phosphorus. From this it can be calculated that every ton of grass grown in a lake can absorb 2-2.4 kilograms of nitrogen. If the lake water is of Class III water quality, with 5 grams of nitrogen per ton of water, one ton of fresh grass can absorb all the nitrogen in 800-1,000 tons of lake water, and can turn thousands of tons of lake water into Class I or Class II water, while one mu of water surface can produce dozens of tons of fresh grass and purify tens of thousands of tons of lake water. If these grasses are used to raise fish, ducks, and geese, they can also generate certain economic benefits. Therefore, when planting aquatic plants, you can purposefully select some aquatic plants with relatively high utilization value, such as Azolla, water lettuce, alligator weed, and water hyacinth. Then stock an appropriate amount of fish, shrimp, and waterfowl in the water, harvest aquatic products in a timely manner, and keep the water body in a relatively stable ecological environment, thereby achieving both environmental and economic benefits.
III. Application prospects of aquatic plants
Thinking back to childhood, by the ponds in the countryside one could see vibrant reeds and Acorus calamus on the banks and floating aquatic plants on the water surface, with the pond water so clear that the bottom was visible, fish swimming back and forth in the water, and in the crevices of the stones along the bank, one could reach in and catch snails and shrimp. Why was the river water naturally clear and transparent then? It was because aquatic plants and small aquatic organisms played a role in purifying water quality during their respective growth and reproduction processes. With the changes of the times, aquatic plants with water purification and landscaping functions have gradually been forgotten, and newly built water conservancy projects show no trace of them. Closed rubble revetments and concrete revetments built with the goal of controlling water flow have sealed off the dream of restoring ecological rivers.
In recent years, Japan, Switzerland, and other countries have proposed the application of "ecological engineering methods" to carry out "multi-natural" renovation and management of overly artificial river channels and water systems. Their basic idea is to follow natural laws and return what belongs to nature back to nature. Through ecological revetments and water landscape greening technology, they improve the comprehensive ecological and landscape benefits of water scenery and provide living environments for animals and plants.
China's water resources are very rich, especially in the middle and lower reaches of the Yangtze River. This region is the main concentration area of freshwater lakes in China (accounting for about 60% of the country's total freshwater lake area), and most of them are shallow lakes. At present, these lakes generally suffer from eutrophication. In addition, with the widespread application of pesticides and chemical fertilizers, the water quality of rural inland rivers is also very seriously polluted, and a large amount of water quality purification urgently needs to be solved; the water quality pollution of urban inland rivers is even more serious, and artificial revetments are common. Recently, large cities such as Beijing, Shanghai, Suzhou, Hangzhou, and Kunming have launched projects to rebuild and restore water body ecological environments and have achieved certain results. Experiments have proved that aquatic plants play an important role in treating lake water, purifying water quality, and restoring water body ecological environments.