What are the cultivation techniques for ginkgo trees? A detailed explanation of key cultivation and management points
The ginkgo tree is an excellent tree species valued both for its fruit and its timber. It has a tall, beautiful form and is also a fine ornamental tree. Ginkgo has strong adaptability to soil, tolerating acid, alkaline and drought conditions, and lives for several hundred years, even over a thousand years; people call it the “grandparent-grandchild tree.” Its fruit is rich in ginkgolic acid and ginkgol, is highly nutritious and can be eaten or used as medicine; the leaves can be used to make drugs such as “guanxintong” (ginkgo flavone), and can also be used as paddy field fertilizer and insecticide. Its wood is light, resilient and fine-grained, not prone to warping or cracking, making it a fine material for construction, crafts and furniture.
Cultivation value
Ginkgo is commonly known as the white fruit tree, the grandparent-grandchild tree or the duck-foot tree. After the late Quaternary glaciation it survived only in China, and it is one of China's important specialty fruit trees. The ginkgo tree has great comprehensive utilization value. Its usable part is the seed kernel, which is highly nutritious, fragrant and glutinous, a premium tonic and an excellent ingredient for fine dishes, and it also has certain medicinal value, with effects such as resolving phlegm, relieving cough, nourishing the lungs, relieving menstrual pain, stopping abnormal discharge, promoting urination and killing bacteria.
The ginkgo tree has a tall and majestic posture, with clean, elegant leaves. It has a certain resistance to smoke and dust pollution and can purify the air, and it suffers from very few pests and diseases, so it is also an important landscape tree and an excellent species for greening around homes and roadsides. It is also used to make stump bonsai.
Ginkgo wood is fine and soft, rich in elasticity and not easily deformed, making it a material for fine crafts and precious household uses; however, it takes far too long to mature and production is relatively low. The leaves can be used to extract the new drug guanxintong for treating diseases of the vascular system; even fallen leaves can be used to stuff medicinal pillows. The fleshy outer seed coat can be used to extract tannin extract, and when mashed and mixed with water it can be made into a homemade pesticide with insecticidal effects.
Main types
Only one genus and one species of ginkgo remains today. In addition, there are varieties such as the leaf-seed ginkgo, in which some seeds grow on the leaves and the seed stalks merge into one. In plant classification, ginkgo belongs to the gymnosperms. The ovules are produced on the seed cupule and are not enclosed by an ovary, so when mature the seeds have no fruit skin on the outside. The drupe-like “fruit” commonly seen is actually the seed of the ginkgo.
Cultivated varieties are usually divided into three categories according to the traits of the seed and seed kernel: Foshou (Buddha's hand), Meihe (plum kernel) and Malin (horse bell).
The seed kernels of Foshou-type varieties are mostly long obovate to elliptical, with ridge lines on both sides but no obvious winged edges. The seed kernel is plump and sweet-tasting.
The seed kernels of Meihe-type varieties are relatively small, often nearly round and slightly flattened, with the dorsal and ventral surfaces often uneven in thickness; the ridge lines on both sides form an ellipse or spindle shape not far from the base, with ridges on the sides but inconspicuous wings.
The seed kernels of Malin-type varieties are elliptical or spindle-shaped, with ridges on the sides but inconspicuous wings. Their form is intermediate between the Foshou and Meihe types.
Growth habits
Ginkgo is a deciduous fruit tree that grows slowly, bears late and lives long. It is dioecious, and often forms a tall crown with a strong trunk and obvious layered structure. Seedling trees mostly have tower-shaped, conical or oval crowns, while grafted trees, when the central leader is absent or its growth is impeded, can begin to develop a semicircular or open-center crown in the later growth stage. The branches within the crown are clearly divided into two types: long shoots and short shoots. Long shoots are formed by several buds at the tips of branches extending upward and outward, and they form the framework of the crown.
Short shoots are formed when buds in the middle and lower parts of branches first produce leaf cluster shoots, which then extend slightly and accumulate year after year, with extremely short internodes; they are also called “scale shoots” or “milk shoots.” Under certain conditions, short shoots can also send out long shoots. In young trees under 10 years old, the proportion of long shoots sent out is relatively high, accounting for about 70% of the total shoots produced. In large trees over 50 years old, the number of long shoots sent out drops sharply and the proportion of short shoots increases markedly, accounting for more than 80% of the total shoots produced, so the crowns of mature large trees are often relatively sparse. Sometimes latent buds on old trees or large branches can also sprout directly to form short shoots.
After reaching fruiting age, the female flowers and male inflorescences of the ginkgo tree cluster respectively on the short shoots of female and male plants. A short shoot bears 5 to 14 leaves, and generally a stout short shoot with more than 6 leaves can form flower buds. The flower buds are mixed buds, terminal, and in spring after sending out an extremely short shoot they bloom in the leaf axils. Each short shoot on a female plant can bear 2-14 seeds (generally 5-6). Whether flower buds can form on a short shoot is related to the nutritional status of the tree and the branch age and growth condition of the base branch on which the short shoot is borne. Generally, short shoots bear the most fruit on base branches 3-12 years old, after which fruiting ability gradually declines.
The bud germination rate of ginkgo long shoots is extremely high. Apart from the several buds at the tip that send out long shoots, the axillary buds on all the other nodes can send out short shoots and form flower buds that bloom and bear fruit, thus very easily producing alternate bearing. However, short shoots on the same base branch sometimes show alternating fruiting. Male inflorescences are borne in the leaf axils of short shoots on male plants, with 4-6 per short shoot.
Propagation methods
Propagation methods for ginkgo trees include seedling propagation, division and grafting, among others; the most widely used in production are division and grafting. Seedling propagation bears late and produces small seed kernels, and is mostly used to grow trees for both timber and fruit, or to grow rootstock seedlings. Seeds can be sown in winter or after sand stratification in spring; about 600 kg to 750 kg of seed kernels are needed per 1,000 sq m of seedbed. When ginkgo seedlings emerge, the cotyledons do not come above the soil, so the soil covering can be appropriately thicker. Seedlings grow quite slowly, and shading is suitable during high summer temperatures. One-year-old seedlings have poorly developed lateral roots and reach only 20 to 30 cm in height. They are not suitable for leaving the nursery or for grafting. Generally they need to be transplanted and grown on for 2 to 3 years, until the seedlings reach 60 to 100 cm in height, before they can leave the nursery.
Division makes use of the sprouts that emerge from the base of the ginkgo plant, carried out in spring during February to March before the sprouts emerge. Taking along some old roots and fibrous roots helps survival. Division-propagated plants reach fruiting age earlier than seedling plants, but still need about 10 years. After being grown on, divided plants can be planted directly in the field, or used as rootstock for later grafting. When dividing, it is best to choose roots from female plants.
The survival rate of ginkgo cuttings is lower than that of tree species that root easily, but propagating by cuttings can save seeds and expand the source of seedlings. Cutting methods are divided into hardwood cuttings and greenwood cuttings. For hardwood cuttings, use one-year-old branches as cuttings, cut them to about 20 cm, trim the lower end into a horse-ear shape, treat with a 30 ppm to 50 ppm naphthalene acetic acid solution (the active ingredient of rooting agents) for 12 to 24 hours, or soak in 50 ppm ABT-1 rooting powder for 1 hour, then insert the cuttings, with a planting depth of about 10 cm.
Ginkgo trees propagated by grafting bear fruit earliest and have a shorter trunk, making them easier to manage. In the past, producing areas mostly used large rootstocks with high-trunk grafting, which was not conducive to mass rapid seedling production and orchard establishment. At present, production mostly promotes grafting on small seedlings, that is, using 2- to 3-year-old rootstock seedlings and grafting at a lower position 30 cm to 50 cm above the ground, with one-year-old branches as scions. The specific grafting methods are mainly cleft grafting and bark grafting. The grafting period is from mid-to-late March to early April.
Planting and management
For ginkgo orchards planted in solid blocks, it is best to choose open land with deep soil and good drainage; low-lying damp sites, sites with heavy salinity and alkalinity, and heavy clay soils are all unsuitable for establishing an orchard. Planting spacing can generally be 4 m to 5 m between plants and rows; if planned dense planting is implemented, the spacing can be further reduced. Ginkgo leaf-harvesting orchards are planted at high density, with a spacing of only 0.7 to 1 m. Ginkgo trees planted sparsely around homes and roadsides mostly develop large crowns, and the spacing can be widened to 6 to 8 m. Ginkgo roots recover slowly after being injured; the larger the sapling, the longer the recovery time. When planting and transplanting seedlings, the root system should be damaged as little as possible, so as not to prolong the recovery period and affect growth and fruiting.
Ginkgo trees grow slowly, and strengthening soil and fertilizer management can accelerate growth. According to the growth condition of the tree, in addition to appropriately increasing the amount of base fertilizer, topdress 1-2 times before sprouting to promote new shoot growth, applying 0.8 kg to 1 kg of compound fertilizer per tree or watering with decomposed human manure and urine. Ginkgo dislikes waterlogging, so attention should be paid to ground drainage during the rainy season.
Pests, diseases and their control
There are not many pests and diseases harming ginkgo; the main ones are leaf blight and trunk rot, both fungal diseases. For leaf blight, spray 2-3 times during the growing season with a 500-fold dilution of 25% carbendazim or a 600-fold dilution of 70% thiophanate-methyl, and promptly sweep up and burn fallen leaves. For trunk rot, alternately use a 500-fold dilution of 25% carbendazim, a 600-fold dilution of 70% thiophanate-methyl, or a 240-fold Bordeaux mixture 2-3 times during the growing season.
The main pests are longhorn beetles, bagworms, thrips and the ginkgo leaf-roller moth. Thrips harm young ginkgo leaves; in the early growth stage spray a 2000-fold dilution of 2.5% deltamethrin EC or a 3000-fold dilution of 20% fenvalerate EC, or use a 1000-1500-fold dilution of 40% dimethoate or omethoate EC for control. The larvae of the leaf-roller moth tie leaves together and bore into short shoots in early summer; the insect bags and rolled leaves can be removed by hand, sugar-vinegar traps can be hung during the adult emergence period to trap and kill them, or a 1000-fold dilution of 50% phoxim EC can be sprayed for control.
Ginkgo bonsai production methods and key cultivation and care points
Ginkgo is a famous long-lived tree species with strong vitality and peculiar leaf shape, easy to propagate by grafting and to shape and prune, making it a high-quality material for making bonsai. Ginkgo bonsai made from ginkgo milk shoots are especially superb, with high ornamental and economic value. Ginkgo is a commonly used tree species in Chinese bonsai; ginkgo bonsai have thick trunks, curved branches, exposed roots, unique shapes, and are vigorous, elegant and full of interest, making them a masterpiece of Chinese bonsai.
Potting soil preparation:
Because the container is limited, the root growth of potted ginkgo is inhibited, and the limited potting soil must contain sufficient fertility to maintain the needs of ginkgo growth and fruiting. Choose loose, fertile garden soil, sift it, add one third fully decomposed organic fertilizer (such as compost, barnyard manure, green manure, etc.), mix in one fifth crushed plant straw, and moisten the above materials with 5% human manure and urine or a 1% urea water solution. The moisture level is reached when the material forms a ball in the hand and crumbles when the hand is opened. Place it in a sunny spot in a pile, cover tightly with plastic film, and ferment at high temperature for 15 to 25 days.
Container selection:
Choose different containers according to different placement locations. For viewing on a desk or windowsill, choose a ceramic or terracotta flower pot about 30 cm in diameter and 30 cm in height with a drainage hole at the bottom; for viewing in a courtyard or on a balcony, containers such as wooden barrels, small boxes, small vats and flower pots can be used. Change the pot once every 1 to 2 years, filling in some new humus potting soil at the same time.
Careful planting:
In spring after the soil thaws and before the seedlings sprout, choose 2-year-old robust seedlings with well-developed lateral roots, no pests or diseases and a base stem of 1 cm to 2 cm, prune the root system, and trim the wounds smooth to help them heal. Before planting, soak the seedling and the new pot in water for a full day and night. First place a small piece of tile over the drainage hole of the flower pot so that it both drains water and does not let soil leak out. Then fill half the pot with soil, higher in the middle and lower around the edges, spread out the seedling's root system, keep the root trunk upright, fill with soil, gently lift the seedling by hand and then shake the pot to let the soil settle, then fill more soil and press firm. The potting soil should be 3 cm to 5 cm below the rim of the pot so that enough water can be poured. Be careful to avoid pouring only half a pot of water, leaving the top wet and the bottom dry, which affects survival and growth. Water thoroughly and place in a cool place to recover.
Grafting and seedling propagation:
Choose excellent early-fruiting and high-yielding varieties for grafting; they can bear fruit three years after surviving. Relatively good varieties include Tancheng No. 3, Dafozhi and Dongting Huang. Before spring sprouting, use cleft grafting, or from July to August use chip budding with wood, spring grafting sprouts the same year, and autumn grafting survives the same year and sprouts the next year after the rootstock is cut.
Pruning and shaping:
Cultivate a suitable tree shape according to one's own appreciation level and aesthetic views. Such as bow shape, two-tier flat-spreading shape, cross shape, spindle shape, etc. For the bow shape, bend wire 2 cm to 4 cm in diameter into a bow shape, fix it on the pot in the second spring, and tie the new branches along the tree shape; shaping is completed in 3 to 4 years. The latter three tree shapes can be achieved by propping, pulling, bending and other measures to fix the branches in the desired positions, shaping and pruning year by year; in the third year, on the sunny side of the upper crown, choose a strong branch and graft a male branch to prepare for pollination.
Fertilizer and water management:
Bonsai cultivation is affected by container size and soil fertility. Water in the pot evaporates relatively quickly, so observe frequently and water in time. Watering frequency should be decided by looking at the potting soil and the leaves, generally once every 1 to 2 days. In hot, dry weather, water the roots once before 8 a.m. and once after 5 p.m. each day, and also spray the leaves to wash off dust, which helps photosynthesis, increases local humidity and meets the physiological needs of ginkgo. After leaf fall in autumn, take out the surface soil in the pot and replace it with loose, fertile nutrient soil, then water to settle it. When sprouting in early spring, apply a bud-promoting fertilizer mainly of nitrogen; at full bloom, spray a 0.1% borax solution; after flowering, during the fruit-swelling period, apply fertilizer mainly of phosphorus and potassium. Fertilizing potted ginkgo should be done in small amounts and frequently, which both prevents root burn and allows full absorption.
Pest and disease control:
The main insect pests of ginkgo are nettle caterpillars and the leaf-roller moth, among others, and the main diseases are root rot and leaf blight. Root disease is generally caused by water accumulating at the roots, while leaf blight is mainly caused by lack of fertilizer and weakened tree vigor, and is also related to high temperatures. Correct control measures should be taken according to the different pests and diseases. Strengthening fertilizer and water management, enhancing tree vigor and improving tree resistance are also effective ways to prevent and control pests and diseases.
Prospects for sapling planting and key planting management techniques
What saplings have good development prospects to plant today? What are the key planting management techniques for small saplings? The planting prospects for saplings are related to the production situation and development trends of flowers and nursery stock.
Based on the current production situation and development trends of flowers and nursery stock, the following types of flowers and nursery stock can serve as leading varieties for nursery owners and seedling growers to choose from for reference:
1. Export-oriented flowers and nursery stock. Because export seedlings are restricted by factors such as market information, export channels and technical requirements, they are still relatively unfamiliar to most nursery operators, but they have great market potential and development prospects. For example: Adinandra and Eurya have good market demand in Japan, and because Japan has no domestic resources it must rely on imports; boxwood has a long history of cultivation and planting in Germany and other European countries and is widely used in European-style gardens, so there is no problem with biological adaptability. Small bonsai such as firethorn, small-leaf podocarpus, Japanese red maple, elm and cypress species, for which domestic resources are abundant, can take the export route. However, in matters such as planting substrate, seedling packaging and transportation, and quarantine standardization, the production norms and requirements of the EU and the destination countries must be followed. Nursery owners are asked to pay attention to this point.
2. Nursery stock for the northern market. Urban greening and ecological construction are national, long-term key tasks. The northern regions north of the Yangtze River and even north of the Yellow River cover a vast area, have relatively poor ecological environments and relatively few original suitable tree species. Therefore, cultivating seedling varieties adapted to grow in northern regions is a very good approach. For example, the hybrid Chinese tulip tree, after years of trial planting in Beijing, has grown well and can serve as a tree species to promote to the north and open up the northern market. Other varieties such as red-leaf plum, cherry blossom, crape myrtle, magnolia, red maple and ginkgo are all suitable for planting in northern regions such as Shandong, Beijing, Hebei and Tianjin. Evergreen seedling varieties such as dragon juniper and large-leaf boxwood, after several years of planting in Beijing, can basically adapt to the climatic conditions of the north. However, attention must be paid to seedling quality; during the seedling cultivation process, excessive vegetative growth should be controlled and phosphorus and potassium fertilizer appropriately increased to improve cold resistance.
3. Traditional characteristic fine nursery stock. The nursery stock of a place cannot lack local traditional characteristic varieties, because the local tree species that have grown naturally for thousands of years are the most representative, and the traditional characteristic varieties are also the most used in actual market applications. Unless there are special landscape needs, the framework tree species of ordinary green spaces are generally local traditional varieties. For example, osmanthus is a native tree species of Hangzhou with cultural connotations, and specialized units have begun to cultivate improved varieties with a long flowering period, large flowers and abundant blooms; the market prospects for these newly segmented varieties are certainly promising. Camphor is in great demand in urban construction and is very suitable as a street tree. Soapberry, plane tree and goldenrain tree are also indispensable greening seedlings in urban landscape construction. The traditional characteristic varieties of Xiaoshan District, such as dragon juniper, large-leaf boxwood, golden-edged boxwood and Chinese juniper, are both very suitable for planting in reclaimed sandy land and have good market potential.
4. New and superior variety nursery stock. New and superior variety nursery stock refers to seedling varieties introduced from elsewhere or domesticated and cultivated from wild resources. Apart from market hype factors, not many of these seedlings can truly become new and superior varieties. A simple way to investigate and determine this is to conduct field observations of the various seedlings introduced and planted in previous years, analyze them according to greening uses, and compare their growth performance. For example, red-leaf photinia, Hong Kong kousa dogwood, small hill firethorn, golden privet, Mediterranean honeysuckle, large-flowered abelia and variegated star jasmine have been accepted by the market in recent years, and the amount of seedlings used has increased year by year. However, these seedlings root and propagate very quickly from cuttings, and are prone to homogenization and structural surplus. Nursery owners should keep abreast of market information during production and adjust their planting structure.
5. Horticultural cultivation and container cultivation. Horticulturally cultivated nursery stock is a new trend, reflecting society's demand for nursery stock after the economy develops to a certain level. Large seedlings cultivated through horticultural methods, shaped by pruning, or directly grown in containers and applied to various green space constructions and garden landscapes can both form a kind of landscape and embody garden art. For horticulturally cultivated seedling varieties, it is advisable to choose evergreen, fine-leaved, compact and pruning-tolerant varieties, such as podocarpus, upright dragon juniper, five-needle pine, Chinese juniper, Japanese red maple, elm, sweetgum, ginkgo, holly and boxwood species. Container-grown large seedlings, however, must be closely integrated with the market, and some street tree species can be chosen, such as camphor, ginkgo, red and white magnolia, red maple, osmanthus, southern magnolia and deodar cedar.
6. Integration of garden-style fruit tree application with leisure and sightseeing. The garden-style application of fruit trees can on the one hand meet the needs of landscaping, and on the other hand bring economic returns to farmland and mountain forest contractors. Some varieties with excellent quality, such as pomelo, bayberry, persimmon, pomegranate, loquat, jujube and Chinese torreya, are all characteristic economic forest tree species with development prospects.
Sapling planting techniques
I. Soil, fertilizer and water management
(1) Orchard soil improvement
Cherry tree roots prefer sandy soil with good aeration and relatively high fertility. When establishing an orchard on hilly land, if the soil was not deeply plowed and improved, combine it with autumn fertilization, increase the application of organic fertilizer to strengthen soil improvement; for clay land, build a good drainage system, pay attention to drainage and waterlogging prevention, and avoid directly pressing in sand; the sand, soil and organic fertilizer must be mixed evenly to improve the soil.
(2) Autumn base fertilizer
Large cherries need fertilizer early and in concentrated amounts in spring. To increase the tree's stored nutrients, applying base fertilizer in autumn is key. According to experiments by relevant experts, concentrated autumn fertilization has the best effect. The base fertilizer should generally be applied in early to mid-September. The amount applied should be determined according to the size of the fruit tree; fruit trees that have entered the fruiting stage generally need 50-100 kg of organic fertilizer per tree, mixed with 2-3 kg of superphosphate, 0.5-0.8 kg of urea, 0.2-0.3 kg of borax and 0.2-0.3 kg of ferrous sulfate. Fertilization method: dig pits or ring-shaped trenches according to the projection of the tree canopy and at a distance from it. In densely planted orchards where roots have filled the garden, dig strip trenches along the outer edge of the canopy projection between plant and row spacing (pits or trenches about 30 cm deep). After the fertilizer is applied, watering must follow, to promote fertilizer uptake with water and facilitate root absorption. After the water stops and seeps down, seal the pits and trenches firmly with soil (commonly called sealing the planting hole), and avoid broadcasting fertilizer over the whole orchard, which causes tree roots to rise to the surface.
(3) Foliar topdressing
Foliar topdressing can extend the functional period of leaves, enabling them to manufacture more nutrients to store in the fruit tree for root growth and for sprouting and flowering the next year. In autumn, from mid-August to mid-September, apply once every 10-20 days, 2-3 times in total. For foliar spraying, use 0.5-0.8% urea or 0.2-0.4% monopotassium phosphate; for young trees growing vigorously in autumn, a 4% wood ash extract can be sprayed alone to promote branch maturity. Spraying must be done after 5 p.m. until evening, when the fertilizer solution evaporates less, adheres to the leaf surface longer and is better absorbed by the leaves, preventing phytotoxicity. When spraying, be careful to spray the underside of the leaves to aid absorption.
(4) Watering before freezing
In November, before the soil freezes, water thoroughly once.
II. Training and pruning
Large cherry pruning includes pulling branches to open the crotch angle, summer pruning and notching buds to promote branching, and clearing the head and removing large branches. For large cherries, the natural open-center form or natural clump form is suitable; these two tree forms take shape quickly, bear fruit early, have shorter trunks, are convenient to manage and harvest, and are also conducive to wind resistance and lodging resistance.
(1) Pulling branches to open the angle. Practice has proved that pulling branches to open the angle in autumn has a better effect than in spring for large cherries. The base angle of the first tier of main branches of large cherry is about 80 degrees, and the tip angle is 65-70 degrees; the angle of auxiliary branches is opened to 80-90 degrees. When pulling branches to open the angle, be careful to move the pull ropes or weights in time to prevent the tip angle from growing inward. When the tree height is 4/5 to 3/4 of the row spacing (row spacing 4 m, tree height 3 m), pull all the upper branches open and no longer head them back; on the upper ends of each main and lateral branch, keep only 1 branch as an extension and another branch as a lateral branch, and the excess long branches can be removed.
(2) Autumn pinching. In late July and early August, when a small number of new shoots appear in the inner part of the tree, pinch them promptly at about 20 cm to control excessive growth, promote maturity and form fruiting branch groups.
(3) Removing large branches, etc. In mid-to-late August, promptly remove upright branches on the upper side, overly dense branches and overly vigorous branches to improve light in the inner part and plump the flower buds. For trees with a hollow inner part, moderately head back 1- to 2-year-old strong branches in the inner part to promote branching and cultivate fruiting branch groups. For the peripheral branches of Dazi, Hongdeng and Binku, keep 1-2 branches growing outward, and remove the rest. Removing large branches should be carried out in mid-September; removing branches during the dormant period easily causes gummosis, so large branches must not be removed then. In one year, remove at most 2 large branches from a tree, but do not create opposing wounds.
III. Improving varieties
Because large cherries have a relatively long juvenile period, and the interval from first fruiting to entering full production is long, improper variety planting or poor combination will affect orchard benefits. This requires improving varieties; grafting is best done by budding in August or by spring branch grafting the next year.
In August, during the gap after the second new shoots of the cherry tree stop growing and before the third new shoots appear, use the chip budding method with wood for grafting. Graft on one- or two-year-old branches for variety improvement. Cherry varieties that can be grafted for conversion include Hongdeng, Italian Early Red, Ukraine No. 2 and Dahong.