How to grow chrysanthemums in the south? Cultivation key points and pest and disease control techniques
There are many varieties of chrysanthemums in China, and they are cultivated in many regions. Chrysanthemums can also treat dizziness and eye pain, externally contracted wind-heat, and so on. At present, the market price of chrysanthemums continues to be around 20 yuan per kg. Below, let us learn together about the propagation methods and pest and disease control cultivation techniques for chrysanthemums in southern regions.
1 Site selection and land preparation
Chrysanthemums have low requirements for the planting soil, and sandy soil with good drainage, looseness and high humus content is better. Clay soil and low-lying saline-alkali land are not suitable for planting, and chrysanthemums cannot be continuously cropped. Apply 50-80 kg of ternary compound fertilizer per mu, and if conditions permit, apply 5,000 kg of organic fertilizer, deep rotary till 2 times, and then press and rake level.
2 Propagation and transplanting
Division propagation is mainly used. In April to May, when chrysanthemum seedlings grow to 15 cm, dig out the whole plant, divide it into several plants, and plant them in the field at a plant spacing and row spacing of 30 cm x 55 cm. After planting, water thoroughly, and water once again half a month later. At the same time, strengthen field management to reduce the occurrence of pests and diseases. Before planting, spray or soak for 2 min with 300-fold carbendazim solution and 200-fold imidacloprid solution. Combine watering with weeding, and irrigate for weed control with 150-300 g trifluralin per mu.
3 Field management
After the chrysanthemums turn green and survive, cultivate the soil in time to prevent wind from escaping through soil cracks. After that, loosen the soil and weed according to general management methods until budding. Generally in July, to prevent excessive growth of chrysanthemums, apply a chemical control treatment with paclobutrazol once. After budding, water thoroughly once, and at the same time supplement trace element fertilizer to lay a foundation for flowering. Chrysanthemums are averse to waterlogging, so drain promptly when there is a lot of rain.
4 Pest and disease control
Common chrysanthemum diseases include root rot, downy mildew and brown spot, among others. Especially in the rainy season, the disease occurrence becomes more severe. They can be controlled with 430 g/L tebuconazole 2,500-fold solution and 80% carbendazim 800-fold solution. Pests are generally aphids, and spider mites occur in some plots. They can be controlled with 10% imidacloprid wettable powder 300-fold solution, 20% acetamiprid 500-fold solution, 1.8% abamectin or spirodiclofen 500-fold solution.
5 Harvesting and drying
Chrysanthemums are generally harvested around Frost's Descent, and the best time is when the flower center has opened 2/3. For medicinal use, cut down the whole plant and bundle it into bundles, stack one stack per half mu, keep it ventilated and dry, and seize the sunny weather to pick the flowers and dry them. It is best when the flowers are white and loose. Chrysanthemums for tea should be promptly covered with a shed to prevent cold damage, and picked and dried in time, following the principle of drying as much as is picked, so as not to affect quality.
Overall, chrysanthemums require little investment, are easy to manage and have relatively high returns, and the planting area is also increasing year by year. However, if you want to obtain high yields, mastering high-yield management techniques for chrysanthemums is key.
Key technical points for field cultivation of chrysanthemums
Chrysanthemum is a perennial herbaceous plant with persistent roots. It likes a climate with abundant sunlight, coolness and no severe cold, and a dry, well-ventilated environment. It requires neutral soil rich in humus, fertile and loose. It is drought-tolerant and tolerant of mild alkalinity, and the suitable growth temperature is 15°C to 25°C. Several key technical points should be mastered when growing cut chrysanthemums in the field.
For variety selection, late-autumn chrysanthemums and winter chrysanthemums that are not easily damaged by freezing can be chosen. They have strong cold resistance, thick and hard petals, thick, upright and straight stems, uniform internodes, and thick, flat leaves. They are suitable for long-distance transport and storage, and after absorbing water they can become upright and rejuvenated again, and after soaking they can fully open and last a long time. For producing cut chrysanthemums in northern China, if they are to be supplied to the market in May, cuttings should be taken for seedling raising in October of the previous year and grown in a greenhouse in winter; if they are to bloom in August to September, seedlings can be raised in March of the same year, and short-day treatment should be carried out 60 days earlier. In the south, supplying cut chrysanthemums in winter and early spring is relatively easy, without the need for a greenhouse, and they can be produced by large-scale field planting, but high beds need to be made to prevent waterlogging. Proper shading at noon in the dry season can increase stem length and facilitate vase insertion.
Preparation before planting. Chrysanthemums are averse to water and moisture. For field cultivation of cut chrysanthemums, deep furrows and high beds must be used, preferably with a bed height of 25 to 30 cm and a bed width of 1 to 1.2 m, and the bed length should not exceed 30 m. Waist ditches should be opened around the field, and the waist ditches should have the function of storing and draining water, so that rainwater does not leave the ditch and no water remains after the rain stops. Cut chrysanthemums grow vigorously and have a high fertilizer requirement. Applying more long-acting organic fertilizer can make the soil loose and promote root growth of the plants. Cut chrysanthemums are averse to continuous cropping, and are also not suitable for continuous cropping with the same crop.
Planting. Cut chrysanthemums are divided into multi-stem and single-stem types. For export-type cut chrysanthemums grown in the field, single-stem cultivation is generally used. In general single-stem cultivation, about 60 plants are planted per sq m, with 4 rows per bed, a row spacing of 25 cm and a plant spacing of 6 cm. When the chrysanthemums grow to 30 cm tall, use 12 x 12 sq cm plastic shallow netting to support the main plants so that the chrysanthemum branches are evenly distributed.
Fertilizer and water management. Watering cut chrysanthemums is very critical. In addition to appropriately increasing watering during the flower bud development period, it should be dry more and wet less, alternating dry and wet, with less furrow irrigation and flood irrigation. Because cut chrysanthemums are planted densely and consume more fertilizer, in addition to applying base fertilizer, they must be topdressed frequently in combination with watering. Generally, before budding, nitrogen and potassium fertilizers are mainly used, and after that phosphorus fertilizer is appropriately applied. Topdressing should be light and frequent to prevent excessive fertilization. When the chrysanthemum plants shift to reproductive growth, fertilization can be paused to facilitate flower bud differentiation. After budding, topdressing should be carried out again.
Pruning and branch training. Keep the strong and remove the weak, remove branches, and remove axillary buds in time to reduce nutrient consumption and ensure that the plants reach a certain height. After budding, promptly remove all side buds below the main bud. During cultivation, if the "willow leaf" phenomenon appears, pinch early and change the growing point so that it sends out new shoots again.
Pest and disease control. The main pests and diseases of cut chrysanthemums are leaf spot and aphids. In the early growth stage, fungicides should be used regularly to prevent the occurrence of various leaf spots. When entering the reproductive stage, prevent powdery mildew and aphids and other damage to flower buds, so as not to affect cut flower quality. Chrysanthemum leaf spot has a very long onset period, continuing from April to October, and is most severe when there is more rain around the Beginning of Autumn. After onset, reduce the number of waterings as much as possible, and spray Bordeaux mixture or zineb 500-fold solution once every week, stopping before the flower buds show color. Aphids should be prevented before occurrence by spraying rotenone, and after occurrence the pesticide should be sprayed two or three times in succession to eliminate them completely.
Supplemental lighting. Late-autumn chrysanthemums and winter chrysanthemums are typical short-day plants, and the length and intensity of light both affect flowering and flower color. Supplemental lighting for chrysanthemums can inhibit flower bud differentiation. Generally, a standard 6 m wide greenhouse can plant 4 beds, and a row of 60-watt incandescent lamps is hung above each bed at intervals of about 1.5 to 2 m, preferably at a height of 90 to 100 cm from the plants. Supplemental lighting is carried out from 23:00 to 2:00 the next day, generally starting at the end of August, and the number of supplemental lighting days should be determined according to the planting time.
Harvesting and cold storage. When the flower buds show 3 to 5 tenths of color, it is the suitable harvest time. Generally harvest in the early morning or evening, which is beneficial for freshness preservation. The harvested chrysanthemums are immediately transported to a freshness-preservation factory for precooling, with the temperature controlled at about 10°C. After precooling, trim the chrysanthemums, generally retaining a stem length of about 90 cm, in units of 10 stems, and send them to the cold storage room. Cold storage is divided into wet storage and dry storage. Wet storage is generally used for short-term storage. The method is to insert the flower stems into a preservation solution. The formula of the preservation solution is 20 g sucrose, 25 mg silver nitrate, and 200 mL 8-hydroxyquinoline citrate per liter of water; dry storage is to place the cut chrysanthemums in plastic bags or paper boxes and store them in a cold storage. Note that they cannot be stored in the same cold storage as fruits and vegetables, so as to avoid ethylene produced by fruits and vegetables affecting flower freshness preservation. The cold storage needs to maintain a relative humidity of 90% to 95%, with the temperature controlled at 0°C to 17°C, and can store them for 3 to 4 weeks.
Introduction to dahlia planting and cultivation
Name: Dahlia
Dahlia aliases: dahlia chrysanthemum, Tianzhu peony, shao peony, sweet potato flower, Dali flower, passionflower, foreign chrysanthemum
Scientific name: Dahlia pinnata Cav.
English name: Dahlia, Garden Dahlia
Family name: Asteraceae Compositae, Dahlia genus
Flower language: Dahlia - great fortune and great profit. French flower language: Dahlia——gratitude, freshness, novelty, new meaning
Dahlia is a perennial herb in the Asteraceae family. Chrysanthemums bloom proudly in frost, but dahlias are different. They bloom successively between spring and summer, bloom again after summer, and wither at Frost's Descent. Their flower shape is similar to that of the peony, which is renowned for its national beauty, and their colors are magnificent and colorful, making them lovable.
Dahlia is the national flower of Mexico, the city flower of Seattle, the provincial flower of Jilin Province, and the city flower of Zhangjiakou City, Hebei Province. The gorgeous and varied dahlia symbolizes elegance, magnificence, and great fortune and great profit. Today, its footprint has spread to countries around the world, becoming a frequent guest in gardens and a world-famous ornamental flower.
Dahlias are easy to propagate. They can be grown from seed, cuttings and root division. They like sunlight and loose, fertile, well-drained soil. Grafting when they just sprout can produce colorful Dali flowers and dahlia chrysanthemums.
Dahlias are suitable for flower beds, flower borders or clustered planting in front of courtyards, and dwarf varieties can be potted. The flowers are used to make cut flowers, flower baskets, garlands, and so on. The tuberous roots contain inulin, which is similar to glucose in medicine. The whole plant can be used as medicine and has the effect of clearing heat and detoxifying.
Dahlia regions
The hometown of dahlia is the Mexican plateau region at an altitude of 1,500 m. It is neither cold-tolerant nor tolerant of severe heat. The climate there is cool and mild, and there is a low-temperature period for dormancy. In places such as Liaoning and Jilin in China, the climate is suitable and dahlias grow well.
Dahlia has thick, hammer-shaped fleshy tuberous roots. Plant height varies among varieties. Leaves are opposite, 1-3 times pinnately parted, with ovate lobes and coarse blunt serrations. Flowers grow at the top of the stalk. Dahlia is welcomed for its long flowering period, blooming continuously from autumn to spring. Each flower can last 1 month, and the flowering period lasts half a year. In southern China, it blooms from February to June in spring.
Dahlia characteristics
Dahlia is also known as passionflower and dahlia chrysanthemum. To cultivate dahlias well, you need to master its four major characteristics:
(1) It likes moisture and fears waterlogging. Dahlia is afraid of drought and averse to water accumulation. This is because dahlia has fleshy tuberous roots, and excessive watering easily causes root rot. However, its leaves are large and its growth is luxuriant, so it also needs more water. If it wilts due to lack of water and water cannot be replenished in time, after exposure to sunlight, in mild cases the leaf edges scorch, and in severe cases the basal leaves fall off. Therefore, watering should follow the principle of “water thoroughly after the soil dries out.”
(2) It likes fertility but fears excess. For planting dahlias, fertile and loose soil should be chosen. In addition to base fertilizer, topdressing is also needed. Usually from mid-to-late July until flowering, apply a dilute liquid fertilizer once every 7-10 days, and the concentration of the fertilizer should gradually increase so that the stems become thicker and stronger and the leaves are dark green and spread out.
(3) It likes sunlight and fears shade. Dahlia likes sufficient sunlight. If placed in a shaded place for a long time, it will grow poorly, with weak roots, thin leaves and slender stems, small and pale flowers, and it may even fail to bloom. Only by planting it in a place with sufficient sunlight can the plants grow robustly and produce bright flowers.
(4) It likes coolness and fears heat. During the flowering period, dahlia likes a cool climate, and grows best at a temperature of about 20°C. In North China and other places, it can grow well from late spring to late autumn. However, it fears direct exposure to the hot summer sun, especially the blazing sun after rain clears. At this time, slight shading should be provided, and then it will grow better.
Dahlia propagation methods
Root division and cuttings propagation are mainly used, and seed propagation is used for breeding.
1. Root division propagation
This method is the most commonly used. Because dahlia can sprout only at the root crown, when dividing, part of the root crown must be included, otherwise new plants cannot sprout. In order to facilitate identification, the pre-buried root method is often used for sprouting promotion, and after the adventitious buds on the root crown sprout, they are divided and planted. The root division method is simple and easy, with a high survival rate and strong seedlings, but the number of propagated plants is limited. 2. Cuttings propagation is the main propagation method for dahlia, with a large propagation coefficient. It is generally carried out in early spring, and also in summer and autumn. The survival rate of cuttings in a greenhouse or hotbed in March to April is the highest. Cuttings are taken from tuberous roots that have been sprouted. When a pair of leaves at the base of the new shoot unfolds, they can be peeled from the base for cutting. They can also be taken by leaving more than one node at the base of the new shoot, and later as they grow, tender shoots from axillary buds can be taken, so that more cuttings can be obtained. Spring cuttings, after full growth through summer and autumn, can bloom in the same year. From early June to August, shoots can be taken from growing plants for summer cuttings, but the survival rate is lower than that of spring cuttings. The survival rate of cuttings from September to October is lower than that of spring cuttings, but higher than that of summer cuttings. The cutting medium should preferably be sandy loam plus a small amount of leaf mold or peat.
3. Seed propagation is limited to flower bed varieties and breeding applications. In summer, seed set is often poor due to heat and humidity, so seeds are mostly collected from those that mature after the weather turns cool in autumn. Drooping-petal varieties are not easy to obtain seeds from and require artificial supplementary pollination. Sowing is generally carried out in a sowing box. At about 20 C, they sprout and emerge in 4-5 days. After true leaves grow, divide and transplant them, and they bloom after 1-2 years.
Cultivation methods
The stems of dahlia are crisp and tender, cannot withstand strong winds, and are also afraid of waterlogging. When planting in the ground, choose a place with high and dry terrain, good drainage, sufficient sunlight and shelter from the wind, and make high beds. The plant and row spacing is generally about 1 m for standard varieties, and 40 cm-50 cm for dwarf varieties. Dahlia stems are tall, juicy and tender, so supports should be set up to prevent wind breakage. Watering should follow the principle of watering only after the soil is dry. If after continuous cloudy days in summer it suddenly clears, promptly spray clean water on the ground and leaves to cool down, otherwise the leaves will develop scorched edges and yellowing. When there is no rain during the dog days, in addition to watering every day, water should also be sprayed to cool down. After buds appear, apply liquid fertilizer once every 10 days until the flower buds show color. Before frost, leave a root crown of 10 cm-15 cm, cut off the branches and leaves, dig up the tuberous roots, dry them in place for 1-2 days, and then pile them indoors and store them in dry sand. The storage room temperature is about 5 C.
For potted dahlias, it is better to repot multiple times. Choose a shallow pot with a large opening, and at the same time make the drainage hole at the bottom of the pot as large as possible, and place a layer of broken tiles underneath as a drainage layer. The culture soil must contain half sandy soil. The last repotting needs sufficient base fertilizer to supply adequate nutrition. Other management is the same as field planting. For cut-flower dahlias, the cultivation key points are the same as field planting, with a plant and row spacing of 50 cm-100 cm. In the peak growth season, topdress with liquid fertilizer once every half month, pinch appropriately, and retain more side branches.
Cultivation management
Cuttings and sowing are mostly used for propagation, with cuttings as the main method, generally carried out in September to October.
① Potting time is generally in mid-October, with 1-2 plants per pot;
② When the seedlings grow to 10-12 cm tall, leave 2 nodes and pinch the top, cultivate 6-8 branches per pot, and carry out the last pinching 40-50 days before Spring Festival, so as to control flowering during Spring Festival;
③ Watering: water 2-3 times a day, and appropriately control water before flowering to promote flowering;
④ Fertilization: mainly apply nitrogen fertilizer in the early stage, and mainly phosphorus and potassium fertilizer in the later stage. Generally apply inorganic fertilizer once every 10 days and organic fertilizer once a month.
⑤ Pest and disease control: spray pesticides regularly to protect the basal leaves;
⑥ Staking with bamboo: after the last pinching and branch setting, begin staking with bamboo, one bamboo strip per branch, and at the same time remove excess side branches for ventilation;
⑦ Bud thinning: when the flower buds grow to the size of a peanut, keep 2 flower buds per branch and remove the others;
⑧ Bud setting: when the flower buds show red, keep only 1 flower bud per branch.
The key to potted cultivation. The key to whether potted dahlias grow well lies in strengthening the management of the plant's potting soil, giving sufficient light, frequently applying water and fertilizer, and timely shaping and pruning management.
(1) Management of potting soil
Dahlia is suitable for loose sandy loam rich in humus and with good drainage. For potting soil for planting potted dahlias, it is generally appropriate to use culture soil prepared from vegetable garden soil (50%), leaf mold (20%), sandy soil (20%) and dried manure (10%). Compacted soil easily causes waterlogging and root rot and cannot be used. In daily management, loosen the soil in time and remove accumulated water in the pot, because the fleshy tuberous roots of dahlia rot when the soil water content is too high and air permeability is poor.
(2) Light
Dahlia likes light and is not shade-tolerant. If placed in a shaded place for a long time, it will grow poorly, with weak roots, thin leaves and slender stems, small and pale flowers, and some may even fail to bloom. Therefore, potted dahlias should be placed in a place with sufficient sunlight. Leaves should be spread out evenly to benefit mutually from sufficient light. Daily light should be more than 6 hours so that the plants are robust and the flowers are large and full. If daily sunshine is less than 4 hours, stem and leaf branching and flower bud formation will be affected to a certain extent. Especially under cloudy and rainy conditions with insufficient light, flowering will be poor, stem and leaf growth will be poor, and they will be prone to disease.
(3) Water frequently
Dahlia likes water but is averse to water accumulation. It is afraid of both waterlogging and drought. This is because dahlia has fleshy tuberous roots, and excessive watering easily causes root rot. However, dahlia has luxuriant branches and leaves and a large evaporation rate, so it needs more water. If it wilts due to lack of water and water cannot be replenished in time, and then it is exposed to sunlight, in mild cases the leaf edges scorch, and in severe cases the basal leaves fall off. Therefore, watering should follow the principle of “water thoroughly after the soil dries out.” Generally, in the early growth stage, the small seedling stage, the water requirement is limited, and on sunny days it can be watered once a day, keeping the soil slightly moist as the standard. Too dry or too wet is unsuitable. In the later growth stage, with luxuriant branches and leaves, more water is consumed. On sunny days or days with north wind, note that water shortage is likely at noon or in the evening, and the amount of watering should be appropriately increased.
(4) Appropriate fertilization
Dahlia is a fertilizer-loving flower. From the seedling stage, generally topdress with dilute liquid fertilizer once every 10-15 days. After budding, apply once every 7-10 days. When the flower buds show color, fertilization and watering should be stopped. Fertilization is also unsuitable when the temperature is high. The amount of fertilizer applied should be determined according to the plant growth condition. If the leaves are light in color and thin, it is a sign of fertilizer deficiency; conversely, if fertilizer is excessive, the leaf edges scorch or the leaf tips turn yellow. Thick leaves with a deep dark green color are a sign of suitable fertilization. The concentration of fertilization should be increased each time so that the stems become thick and strong.
(5) Shaping and pruning in pots
The branch training of potted dahlias should be flexibly controlled according to the variety. Generally, large varieties use single-stem shaping, and medium varieties use 4-stem shaping. Single-stem shaping means retaining the terminal bud and removing all axillary buds so that nutrients are concentrated, forming a short single-stem dahlia with large flowers. For 4-stem dahlia, pinch the seedlings, retain two nodes at the base, and let them form 4 side branches. Each side branch retains its terminal bud, forming a potted dahlia with 4 stems and 4 flowers.
(6) Inserting stakes to support the plants
The stems of dahlia are both hollow and brittle, and are easily blown down and broken by wind, so bamboo should be inserted in time for support. Inserting bamboo can also prevent the branches from growing curved and improve the ornamental value of the potted plant. When the plants grow to more than 30 cm tall, insert a small bamboo beside each branch and tie and fix it with hemp thread (or thin string). As the plants grow taller, replace them with longer inserted bamboo in time. The last inserted small bamboo should support the lower part of the flower bud. (7) Protecting the plants for safe overwintering. Dahlia is not cold-tolerant (mainly because the tuberous roots cannot freeze). In November, when the branches and leaves wither, cut off the aboveground part, move it indoors, and store it in the original pot. The tuberous roots can also be taken out, dried for 1-2 days, and buried indoors in slightly moist sandy soil, with the temperature not exceeding 5 degrees, and then potted and planted again in the following spring.
Dahlia pest and disease prevention
The pests and diseases that are likely to occur during dahlia cultivation include: powdery mildew, flower rot, stem borer moth, and red spider mite.
(1) Dahlia powdery mildew
The disease is severe from September to November, and high temperature and high humidity will promote the occurrence of the disease. After being affected, the plants are short, the leaf surface is uneven or curled, and the young shoots develop abnormally. After the flower buds are affected, they cannot bloom or can only produce deformed flowers. When the disease is severe, it can cause the leaves to dry up and even the whole plant to die.
Control methods:
① Strengthen maintenance so that the plants grow robustly and improve disease resistance. Control watering and increase phosphorus fertilizer.
② When the disease occurs, promptly remove diseased leaves, and spray with 50% amobam aqueous solution 800-fold or 70% thiophanate 000-fold for control.
(2) Dahlia flower rot.
It mostly occurs from full bloom to the flower-falling period. When soil moisture is relatively high and ground temperature is relatively high, it is favorable for the occurrence of the disease. When petals are affected, the lesions are initially faded green spots, then turn yellow-brown. After the lesions expand, they become irregular, yellow-brown to gray-brown.
Control methods
① Strengthen ventilation and light transmission between plants; in the later stage, water and nitrogen fertilizer should not be used excessively, and phosphorus and potassium fertilizers should be increased.
② After the bud stage, spray with 0.5% Bordeaux mixture or 70% thiophanate 1,500-fold, once every 7-10 days, with good control effects.
(3) Dahlia stem borer moth
This insect mainly harms dahlias and chrysanthemums, with larvae boring into the stems to cause damage. When the damage is severe, the plants cannot bloom and may even be ruined.
Control method: generally from June to September, spray 90% trichlorfon original powder 800-fold about once every 20 days, which can kill newly hatched larvae.
(4) Red spider mite
Red spider mite, namely carmine spider mite, can be referred to in the control section on carmine spider mite in “jasmine.”
Dahlia is a perennial herbaceous flower with persistent roots in the Asteraceae family. Leaves are opposite, 1-3 parted, with serrated leaf margins. Capitulum terminal, with flower colors such as purple-red, peach-red, pink, and bicolor. (5) Dahlia cotton leafhopper pest
Damage: adults and nymphs suck sap on the back of plant leaves, causing yellow-brown spots on the leaf surface, and the leaves shrink toward the back. In severe cases, the whole leaf changes color and scorches.
Control methods: A. Combined with pruning, cut off damaged branches and leaves and dispose of them to reduce insect sources. B. During the adult damage period, use light traps to kill adults. C. During the occurrence period of nymphs and adults, spray 90% crystal trichlorfon 1,000-1,500-fold, or 40% omethoate emulsifiable concentrate 1,000-1,500-fold, or 2.5% deltamethrin emulsifiable concentrate 1,500-2,000-fold for control. The number of sprays depends on the insect situation, generally once every 10 days or so.