Rhododendron cutting propagation method, high survival rate and blooms the following year

As one of China's top ten famous flowers, the rhododendron's reputation is known to everyone; its beauty has won people's hearts and become a symbol of beauty. And to have rhododendrons blooming in more places, we need to master its propagation methods. So how do rhododendrons propagate? It is understood that the propagation methods of rhododendrons mainly include cuttings, grafting, layering and sowing, among which cuttings are the most commonly used. Let's take a look together!

I. How rhododendrons propagate: cuttings / grafting / layering / sowing

If you are a flower lover who loves rhododendrons, after mastering the cultivation methods of rhododendrons, you should also understand the propagation methods of rhododendrons, because only in this way can your home be surrounded by rhododendrons of various colors, and that beautiful scene is truly worth looking forward to. How do rhododendrons propagate? There are four methods: cuttings, grafting, layering and sowing.

Among these 4 rhododendron propagation methods, the most commonly used is cuttings, with a very large propagation quantity; grafting propagation is the most complex, and grafting is only used for varieties that are difficult to root from cuttings; layering propagation produces the fastest mature plants; sowing is mainly used for breeding varieties. Because for ordinary flower lovers, cuttings are the simplest, so next we will introduce the rhododendron cutting propagation method in detail.

II. The cutting propagation method of rhododendrons

① Rhododendron cutting time: May and October

To achieve a high survival rate in rhododendron propagation, choosing the right time is key. Generally speaking, the best time for rhododendron cuttings is in spring (May) and autumn (October), when the temperature is between 20-25°C, which is most suitable for cuttings.

② Cutting substrate

In the rhododendron cultivation methods and precautions, its soil requirements have already been introduced, and the substrate used for propagation at this time is the same. The specific mix: 3 parts leaf mold, 1 part garden soil, and 6 parts river sand mixed together, or 5 parts leaf mold and 5 parts river sand (or pure sand) will also do. Everyone can decide according to the situation, and choose whichever is convenient.

③ Selection of cuttings

Besides timing, the selection of cuttings is extremely critical. Once chosen well, the rhododendron cutting propagation is basically 90% complete. Flower lovers should choose the current year's growth, semi-lignified, robustly developed rhododendron branch tips as cuttings. Use a sharp knife to cut 6-10 cm with nodes, and the cut should be smooth. If there are leaves, the lower leaves should also be trimmed off, leaving only a few leaves at the top.

Treatment of cuttings: After selecting the cuttings, flower lovers should also carry out disinfection treatment: dip the cut end of the cutting into medical vitamin B12 solution, then take it out and let it dry for 2-3 minutes. Doing this can advance rooting by about 10 days, and there will be more roots and faster growth. When using rhododendron cutting propagation, everyone must give this a try~

④ Rhododendron cutting method

After completing the above preparatory work, you can begin the actual cutting propagation. At this time, flower lovers can use chopsticks or a small wooden stick to make a hole in the prepared substrate, then insert the cutting into the hole. Afterward, gently press it firm with your hand and spray thoroughly with water so that the base of the cutting closely combines with the soil.

⑤ Watering rhododendron cuttings: once each in the morning and evening

The above is the cutting propagation method for rhododendrons, but it is not over once done, because post-cutting care is very important. After the cuttings are completed, flower lovers should cover the flowerpot with a plastic bag, seal it all around, then place it in a shaded place, and water once each morning and evening. Stop after one week; just keep the pot soil moist regularly.

⑥ How long do rhododendron cuttings take to root? 40 days

After completing the above steps, maintain shade within one month, and sprouts will appear before long. After that, move them to a bright place to receive scattered light. Besides light, the temperature should also be maintained at 18-25°C. Generally speaking, after doing this, they can root in 40-60 days. So how long do rhododendron cuttings take to root? At the earliest, about 40 days.

Introduction to rhododendrons

  Rhododendron - the beauty of flowers, scientific name Rhododendron simsii & R.spp. Aliases: Yingshanhong, mountain pomegranate, mountain azalea, red azalea, mountain rhododendron, etc. Family and genus: Ericaceae, Rhododendron genus. Rhododendron is one of China's top ten famous flowers.

  Among all ornamental flowers and trees, the one that can be called beautiful in both flower and leaf, suitable for both ground planting and pot cultivation, and with the widest uses, must be the rhododendron. In the natural distribution of rhododendrons in the world, none can match China in the number of species and the huge quantity. China is a treasure house of the world's rhododendron resources! Rhododendron is a large genus, with about 900 species worldwide, distributed in Europe, Asia and North America, with the most in Asia, 850 species, among which China has more than 530 species, accounting for 59% of the world's species, especially concentrated in the Hengduan Mountains area of Yunnan, Tibet and Sichuan, which is the origin and distribution center of the world's rhododendrons.

  In different natural environments, rhododendrons form different morphological characteristics, with extremely wide differences. There are evergreen large trees, small trees, evergreen shrubs, and deciduous shrubs. Some have thick and large trunks, reaching more than 20 m in height, while some are creeping, cushion-like or epiphytic types, only 10-20 cm tall.

  The basic form is: trunk upright, single or clustered; branches alternate or falsely whorled. Branches and leaves hairy or not; branches, leaves and pedicels scaly or not; leaves varied in shape, but not linear, entire, very rarely finely serrate, leathery or papery, evergreen, semi-evergreen or deciduous, fragrant or not; flowers terminal, lateral or axillary, single-flowered, few-flowered or more than 20 gathered into racemose umbels, flowering before leaves or after leaves, corolla conspicuous, funnel-shaped, bell-shaped, radiate salverform bell-shaped, dish-shaped to bowl-shaped or tubular, 4-5 lobed, also 6-10 lobed; flower colors rich and varied; throat with dark spots or light-colored halo; base with honey gland or not; fragrant or odorless; calyx cup-shaped, 4-5 lobed, persistent; stamens 5-10, rarely 10-25, unequal in length, filaments hairy or not, dorsifixed anthers, opening by apical pores, ovary superior, 5-10 locular, style and ovary hairy or not, glandular or not; capsule dehiscing into 5-10 valves, seeds numerous, mostly powdery or chaff-like.

  Classification of original species. The entire genus is divided into 5 subgenera and 8 sections, among which 3 sections are further divided into 58 subsections, and under the sections are species. Namely:

  I. Subgenus Hymenanthes (evergreen scaleless rhododendrons): 1. Section Hymenanthes, divided below into 24 subsections.

  II. Subgenus Rhododendron (evergreen scaly rhododendrons): 1. Section Rhododendron, divided below into 27 subsections. 2. Section Pogonanthum 3. Section Vireya, divided below into 7 subsections.

  III. Subgenus Pentanthera, China has only 1 species.

  IV. Subgenus Tsutsusi, 1. Section Brachycalyx 2. Section Tsutsusi

  V. Subgenus Azaleastrum, 1. Section Azaleastrum 2. Section Choniastrum

  The above 3 subgenera I, II and V are customarily called evergreen rhododendrons, and the 2 subgenera III and IV are called deciduous rhododendrons.

  Several evergreen rhododendrons are introduced below:

  Rhododendron delavayi: aliases Maying flower, horse-nose tassel, cow-blood flower, dog-blood flower, red camellia, dense-barrel flower. Evergreen shrub to tree, tree height 2-15 m, DBH up to 40 cm, bark grayish brown, thick, peeling off in irregular flakes. Leaves leathery, oblong-lanceolate, back densely covered with grayish white to light brown spongy thin tomentum. Flowering period February-May, terminal spherical umbels, with 10-20 flowers, corolla bell-shaped, 3.5-5 cm long, fleshy, deep rose red, stamens 10, ovary 10-locular. Fruit ripens October-November. Produced in Yunnan, Guizhou, Guangxi and other provinces and regions; also distributed in Myanmar.

  Rhododendron fortunei: aliases Tianmu rhododendron, Yunjin flower. Evergreen shrub, 2-4 m tall, branchlets stout, light green. Leaves thick leathery, oblong to oblong-elliptic or obovate, leaf surface dark green, back light green, hairless. Flowering period May, terminal racemose umbels, with 6-12 flowers, fragrant, corolla funnel-shaped bell-shaped, 4-5 cm long, 7-9 cm in diameter, light pink, lobes 7, rounded, stamens 14, ovary 10-locular; pedicels, calyx, corolla base, ovary and style all have glands. Fruit ripens October-November. Seeds numerous, chaff-like. Produced in mountain forests at altitudes of 600-2000 m in Zhejiang, Anhui, Jiangxi, Fujian, Guangdong, Guangxi, Hunan, Sichuan and other places. In recent years, it has been successfully introduced into gardens in Hangzhou, Wuxi, Shanghai and other places.

  Rhododendron giganteum: also known as big mountain dog whole flower. Evergreen large tree, up to 25 m tall, DBH 60-100 cm, maximum basal diameter up to 3 m. Bark light dark brown, peeling off in flakes; branchlets stout, covered with light gray felt-like hairs. Leaves leathery, oblong to oblanceolate, 24-34 cm long, apex obtuse, base broadly cuneate, surface dark green, back light green. In February-March, terminal racemose umbels are produced, with 24 flowers, corolla bell-shaped, 5.5-8 cm long, 6-8 cm in diameter, pinkish red, lobes 8, rounded, base with 8 nectary sacs, stamens 16, ovary 16-locular, densely tomentose. Fruiting period October-November. Produced in the mountain evergreen broad-leaved monsoon forest at an altitude of 2400-**** m in Gaoligong Mountain, Tengchong County, Yunnan. It was first collected in Hetou, Tengchong in 1915 by the Englishman G. Forrest, who sawed off a wood disc with a circumference of 2.6 m and 280 annual rings, now kept in the British Museum in London. It was published as a new species in 1926, and for a long time it could not be found in China, until 1983 when Professor Feng Guomei and others rediscovered it in Tengchong, and the following year found a large tree with a basal diameter of 3.07 m. This is the tallest rhododendron tree in the world, known as the "king of rhododendrons."

  Rhododendron ovatum: aliases ovate-leaved rhododendron, Qingming flower. Evergreen shrub, 2-4 m tall. Leaves leathery, broadly ovate, 3-3.5 cm long, apex acute to obtuse, with a protruding tip, base rounded. Flowering period March-May, flowers solitary in leaf axils, pink, rose red, light purple or purple-white, 5-lobed, 3 cm in diameter, throat pubescent, stamens 5, ovary 5-locular. Fruiting period August-October. Produced in hillside shady sparse forests or valley thickets at altitudes of 500-1200 m in Jiangsu, Zhejiang, Anhui, Jiangxi, Hubei, Hunan, Fujian, Guangdong, Guangxi, Sichuan, Guizhou and other provinces and regions. Horticultural varieties: about two to three hundred horticultural varieties are currently widely cultivated in China. Because their main bloodline is Yingshanhong, although they do not shed leaves in winter, they are still classified as deciduous rhododendrons. According to morphology, traits, parents and origin, they are divided into 4 types: East azalea, hairy azalea, West azalea, and summer azalea.

  East azalea: namely Oriental azalea, because it comes from Japan. Also called Shiyan, cinnabar rhododendron, spring azalea small-flowered type, etc. This category includes Rhododendron obtusum and its varieties, with very many cultivars. Its main characteristics are: small stature, 1-2 m tall, scattered branching, thin and light-colored leaves, few hairs and glossy, flowering in April, densely flowered, the smallest flowers, generally 2-4 cm in diameter, up to 6 cm at most, single or hose-in-hose formed by petaloid calyx, rarely double, flower colors various. Traditional varieties include 'Xintiandi', 'Xueyue', 'Bizhi', 'Rizhichu', and 'Sijizhiyu' which can bloom twice in spring and autumn, etc.

  Hairy azalea: commonly known as hairy-leaved rhododendron, large-leaved rhododendron, spring azalea large-leaved type, etc. This category includes Rhododendron pulchrum, Rhododendron mucronatum and their varieties and hybrids. The plants are tall, reaching 2-3 m, grow robustly, and have strong adaptability. They can be planted in the open ground and are excellent rootstocks for grafting West azaleas. Young branches are densely covered with brown bristles. Leaves up to 10 cm long, rough and hairy. Flowers large, single, broadly funnel-shaped, rarely double, colors include red, purple, pink, white and mixed colors, etc. There are more than 10 varieties, and the most cultivated include 'Yuhudie', 'Zihudie', 'Liuqiuhong', 'Yuling', etc.

  West azalea: first bred in the Netherlands and Belgium in Western Europe, hence called Western azalea, abbreviated as West azalea. It is derived from complex hybridization of Rhododendron indicum, Yingshanhong and Rhododendron mucronatum, etc., and is the type with the most and most beautiful flower colors and flower forms. Its main characteristics are short and sturdy stature, compact crown, delicate habits, afraid of sun and freezing. Leaves thick, dark green, few hairs; leaf shapes include glossy leaf, pointed leaf, twisted leaf, long leaf and broad leaf. Flowering period April-May, flower colors diverse, including solid color, flying white, edged, dotted red, bright spots, sand-sprayed, brocade-sprinkled, etc. Most are double or semi-double, rarely single. Petals include narrow-long, round-broad, flat, recurved, wavy, flying, crinkled-edge, rolled-edge, etc., 6-8 cm in diameter, the largest can exceed 10 cm. Traditional varieties include 'Huangguan', 'Jinpao', 'Tiannvwu', 'SihaiBo', etc. In recent years, a large number of new hybrid varieties have appeared.

  Summer azalea: native to India and Japan, called Rhododendron indicum in Japan. It sends out branches first and blooms latest, generally from late May to June, hence the name. Its main characteristics are slender branches and leaves, dense branching, full and neat crown, about 1 m tall. Leaves narrow and small, closely arranged. Flowers broadly funnel-shaped, 6-8 cm in diameter. Flower colors and petals are as rich and variable as those of West azalea. Flowers are single, semi-double and double, and it is a good material for making bonsai. Traditional varieties include 'Changhua', 'Dahongpao', 'Chenjiayinhong', 'Wubaolüzhu', 'Zichendian', etc. Among them, 'Wubaolüzhu' has a small flower within the flower, appearing in a terrace-like form, and is the rhododendron with the highest degree of doubleness.

  The main producing area of rhododendrons in China is the Hengduan Mountains in Yunnan, Tibet and Sichuan. Its intricate topography and landforms create a special climate, with extremely uneven rainfall distribution, dry winters and springs, rainy summers and autumns, and obvious vertical distribution.

  In low flat valleys at 1000-2000 m, there are Rhododendron moupinense, Rhododendron giganteum, etc.; at 2000-2800 m, the climate is cool, with Rhododendron microphyton, Rhododendron crassistylum, Rhododendron yunnanense, Rhododendron racemosum, etc. At 2800-**** m in sunny slopes of ravines, there are mixed forests of evergreen broad-leaved and deciduous broad-leaved trees. At their forest edges or grassy slopes, Rhododendron wardii, Rhododendron niphophilum, Rhododendron anthosphaerum, Rhododendron trichostomum, Rhododendron pratense, etc. form impenetrable rhododendron forests or thickets. Here rhododendrons have the most species, with flowering from April to July, in all colors, brilliant like brocade, sometimes covering an entire mountain top for one to twenty sq km. In the 4000-**** m zone, there are very few trees and shrubs; multi-branched rhododendrons 10-20 cm tall, such as Rhododendron fastigiatum, Rhododendron prostratum, Rhododendron aureum, etc., become cushion plants, multiplying on gravelly grave ground or scree slopes. Above 4500 m there is no rhododendron distribution. Alpine evergreen rhododendrons have long grown in humid, cool, high-altitude mountainous areas, so introduction must create similar environmental conditions, such as no water accumulation on the ground, soil pH 5-6, good permeability, rich in organic matter, and equipment for shading, misting and cooling.

  Yingshanhong is the representative of deciduous rhododendrons and has the widest distribution, from Henan and Shandong in the north, to the Pearl River basin in the south, to Fujian and Taiwan in the east, and to Sichuan, Yunnan and Guizhou in the west. It can be found in high mountains, low hills, shady and sunny slopes, stream valleys and mountain rocks, forests and forest edges, and grassy thickets. In Jiangnan it blooms in March-April, a bright red expanse. Mountain villagers use it as firewood, and it repeatedly sprouts after repeated cutting, which fully shows its strong adaptability and vitality. In the past, transplanting was difficult to keep alive, which was related to not pruning heavily. Although horticultural varieties have been improved artificially, they still reflect the basic habit of the original species: cold-resistant and afraid of heat, and they require fertile acidic, loose and permeable soil. Some rhododendrons live very long, such as the large tree rhododendron in Yunnan over 500 years old, and the Rhododendron pulchrum planted outdoors in Wuxi for more than 50 years.

  Rhododendrons set seed in high quantities, have many seeds, and a high germination rate. Seed collection can obtain a large number of offspring, and seedlings have strong plasticity and vitality, making this an important means of introduction and breeding.

  (1) Seed collection: When the capsules turn green-brown or yellow-brown in autumn, they can be harvested, placed indoors to dry, and after they split, the seeds are shaken out and stored in a dry place indoors. Sow the following spring.

  (2) Sowing: Use a shallow pot, wooden box or ground bed, with well-drained coarse-grained soil spread at the bottom, and the surface layer 2 cm using orchid soil or leaf mold (both need disinfection). After the seeds are evenly scattered, cover thinly with a layer of fine soil. Or spread 0.5-1 cm of crushed sphagnum on top of the orchid soil, sow the seeds directly into the sphagnum, and do not add cover. Then water to moisten the pot soil, cover with plastic film or a glass plate, and place in a shady place.

  (3) Management: Before emergence, keep the pot soil moist. Generally at 15-20°C, emergence occurs in about 20 days, with a germination rate of 75-85%. After that, the cover can be removed, attention should be paid to ventilation, and the resistance of the seedlings should be improved. When dry, spray moist with a fine nozzle, and do not wash down the seedlings.

  (4) Seedling separation: Deciduous rhododendrons grow relatively fast. When 2-3 true leaves have grown, they can be transplanted for the first time, with a plant spacing of 2-3 cm. After autumn, when they grow to 2-3 cm tall, dig them up again and transplant into 3-inch small pots, 3 plants per pot. The following year, divide and plant again according to growth conditions. Generally, flowers can be seen in 3-4 years. Evergreen rhododendrons are first transplanted after autumn, and transplanted again the next autumn. During the seedling stage, strong light, heavy rain and strong wind should be avoided; the soil should not be too wet, and watering should still be done by misting.

  Cuttings: This is the most widely used method. Its advantages are simple operation, high survival rate, fast growth and stable traits.

  (1) Cuttings: Take current-year tender branches that have just become woody, pull them off with a heel, trim the frayed end smooth, cut off the lower leaves, and keep 4-5 leaves at the top. If the branch is too long, the tip can be cut off. If they cannot be inserted immediately after collection, wrap the base with a wet cloth or moss, cover with plastic film, and place in a shady place, where they can be stored for several days.

  (2) Time: In Jiangnan, cuttings are taken before the plum rain season, giving the highest survival rate. West azalea in late May to early June, hairy azalea in early to mid-June, East azalea and summer azalea in mid to late June. At this time the cuttings are moderately tender, the weather is warm and humid, and the survival rate reaches more than 90%.

  (3) Method: For a small quantity, pot cuttings can be used; for a large quantity, bed cuttings can be used. The medium can be orchid soil, Huangshan soil, river sand or pumice, perlite, etc. It is required to have few pathogens, no weeds, and no fertilizer mixed in. Insert the cuttings 1/3 to 1/2 deep. After inserting, spray with a fine-hole pot and place under a shade frame. The bottom of the pot needs to be raised by a brick; the cutting bed is 20 cm deep, and the bottom of the bed is filled with a 7-8 cm thick drainage layer to facilitate drainage.

  (4) Management: Within one month after cutting, the focus is on shading and spraying water so that the cuttings remain fresh throughout. Avoid rainwater impact during heavy rain, pay attention to drainage during consecutive rainy days, spray 1/1000 thiophanate to prevent black spot disease, and in high-temperature seasons increase water spraying on the ground and leaves, and pay attention to ventilation and cooling. Hairy azalea, East azalea and summer azalea root quickly, about 1 month or so; West azalea needs 60-70 days. After rooting, the top shoots sprout; if flower buds form, they should be removed. After September, reduce shading so that the seedlings gradually become sturdy, and in October thin fertilizer can be applied. In late October they can be potted. If an electronic leaf automatic misting device is installed on the cutting bed, and the medium uses vermiculite or perlite, then shading is not needed. Under full sun, roots form in more than 20 days, the survival rate is more than 95%, and they can be transplanted in 2 months.

  Grafting: This is used more when cultivating West azaleas. Its advantages are: the scion only needs a section of young shoot; young shoots can be grafted at any time, without restriction; several varieties can be grafted onto the same plant; and it grows faster and has a higher survival rate than cuttings. There are many grafting methods, and the most commonly used is terminal cleft grafting of young shoots, best in May-June, with a survival rate of 90%.

  (1) Rootstock: Choose 2-year-old single-stem hairy azalea, requiring the new shoot to be similar in thickness to the scion. Among hairy azalea varieties, 'Yuhudie' and 'Zihudie' are best; generally the original species Rhododendron mucronatum is not used.

  (2) Scion: From the mother plant of West azalea, cut 3-4 cm long young shoots, remove the lower leaves, keep 3-4 small leaves at the top, and cut the base into a wedge shape, with the cut surface 0.5-1 cm long.

  (3) Method: Cut off the current-year new shoot of the hairy azalea at 2-3 cm, remove the leaves from that section, make a longitudinal cut of 1 cm, insert the scion, align the cortical layers, bind with plastic film tape, and put the joint together with the scion into a plastic film bag, then tie the bag tightly.

  (4) Management: Place under a shade frame, avoiding direct sunlight. Pay attention to whether there are water droplets in the bag; if not, open it and spray the scion moist, then tie it tightly again. If the scion does not wilt for 7 days, there is a good chance of success. Remove the bag after 2 months, and untie the binding the following spring.

  Site: Cultivating West azaleas requires two environments, indoor and outdoor: indoor is for winter cold protection, with the lowest temperature not below -2-3°C. Outdoor is for getting through the hot summer. In the Jiangnan region, from mid-April to early November they are all kept outdoors, requiring natural shade from deciduous trees, or artificially built shade frames, to create a semi-shady and cool growing environment. The ground should have a drainage slope, and flower pots should be placed on shelves.

  Pot selection: In production, earthenware pots with good permeability and low price are all used. Rhododendrons have shallow roots and slow expansion, so cultivation should use small pots as much as possible to avoid uncontrolled watering and unfavorable growth. Regarding plant age and pot mouth size, refer to the following table: 1-2 years old: use 3-inch pots; 3-4 years old: use 4-inch pots; 5-7 years old: use 5-inch pots; 8-10 years old: use 6-inch pots; 11-15 years old: use 7-8 inch pots; 16-20 years old: use 9-inch pots; over 20 years: use 10-inch pots.

  Soil: Commonly used is black mountain soil (orchid soil), black in color and light in texture is best. When using, spread it out and sun-dry for several days, pick out debris, sieve out coarse and fine grades, and pot in layers to ensure smooth drainage. In addition, peat soil, Huangshan soil, leaf mold, pine needle soil, and even mixed soil prepared with coal cinders, sawdust, etc., can all be used as long as the pH is between 5.5-7, with good permeability and drainage, and rich in humus.

  Potting: Generally carried out in spring when moving out of the house or in autumn when moving into the house. Fill the bottom of the pot with a drainage layer of coarse-grained soil. After potting, place in a bright place for several days to settle, then move to an appropriate position. During the seedling stage, repotting is more frequent, once every 2-3 years. After 10 years, it can be changed once every 3-5 years. Old plants can go many years without repotting as long as no problems arise.

  Watering: This should be flexibly controlled according to weather conditions, plant size, pot soil dryness and wetness, and growth and development needs. The water quality should not contain alkalinity and should be clean and hygienic. If using tap water to water flowers, it is best to store it in a vat for 1-2 days, and the water temperature should be close to the pot soil temperature. After November, the temperature drops and growth slows, so the water requirement is low; when the room is not heated, it is no problem not to water for 3-5 days. In late February, growth gradually rises, and the water amount should be appropriately increased. From March to June, flowering and shoot growth require a large amount of water; on sunny days, water once daily, and if insufficient, replenish water in the evening. In the plum rain season, during consecutive rainy days, promptly tilt the pot to drain water. In the high-temperature season of July-August, water as soon as it dries, and spray water on the ground and leaves at noon and in the evening to cool and increase humidity. In September-October the weather is still hot, so watering cannot be neglected.

  Fertilizing: West azaleas require light fertilizer applied frequently. Commonly used fertilizers are grass juice water, fishy water, and rapeseed cake. Grass juice water is made by composting tender grass and leaves, is the lightest nitrogen fertilizer, and can be used as water for watering. Fishy water is made from fish offal, heads and tails, and spoiled fish and shrimp, etc., adding 10 times water, storing in a vat, and sealing to ferment for more than half a year. When using, take the original liquid and add water, applying at a concentration of 3-5%. This fertilizer is rich in phosphorus and can make leaves glossy and flowers bright, but the next day it should be rinsed once with clear water. Rapeseed cake is a comprehensive fertilizer, also needing to be crushed and composted for several months, then mixed with water before application.

  Shading: West azaleas need shading from May to November. The frame height is about 2 m, and the reed curtain has a light transmittance of 20-30%. The west side should also have a curtain hung for shading. The daily shading time can refer to the following table: May 9:00-15:00; June 8:30-16:30; July-August 8:30-17:00, with curtains hung at the southeast corner in the morning and the southwest corner in the afternoon; September 8:00-16:00; October 9:00-15:30; November cover appropriately at noon, and do not cover after mid to late month; December-April, if the flowering period needs to be delayed, then cover with a curtain. In this way, West azaleas can bloom as late as late April and reach full bloom on "May Day."

  Pruning: Within 2-4 years, seedlings, in order to accelerate the formation of the framework, often have flower buds removed, or are pinched when new shoots grow to 4-5 cm to promote the sprouting of side branches. Some varieties have short and numerous new shoots, so pinching is not suitable, and instead branches should be thinned appropriately. Plants 5-10 years old should not bloom too much, and some flower buds should also be removed. After growing into large plants, the main task is to cut off diseased branches, weak branches and branches that disrupt the tree shape, all mainly by thinning cuts.

  Flowering period management: When West azaleas bloom, place them indoors, free from sun and rain, and they can last 1 month. If indoor ventilation is poor, they should not be kept for long, and should be changed after one or two weeks. West azaleas form buds in July-August, enter the house after autumn, maintain 20°C, and can bloom after half a month. Accordingly, they can be made to bloom on New Year's Day and Spring Festival. If kept continuously in a low-temperature cold room at 3-4°C and taken out in mid-September, they will bloom on National Day. After flowering, remove the spent flowers promptly, and add pruning, and take good care.

  Pest and disease control: The most common pests are red spider mites and lace bugs. Red spider mites are seriously harmful in high temperature and dry conditions from June to August, often causing leaves to turn yellow and fall off; they can be sprayed and killed with 1/1000 dicofol, once a week, for 3 consecutive times. From May to October there is damage by lace bugs, which spreads faster in dry climates, and can be sprayed and killed with 1/1500 dimethoate or dichlorvos. Brown spot disease is the most common disease, mainly occurring in the plum rain season. Brown patches appear on the leaves, infecting repeatedly, causing great harm, and it is the main cause of leaf fall. The control method is: spray 1/800 thiophanate or Bordeaux mixture of equal amounts before and after flowering, pay attention to improving light conditions, strengthen ventilation, and burn diseased leaves at any time.

  Artificial pollination hybridization is a conventional breeding method. Varieties with well-developed pistils and high fruit-setting rates should be selected as the female parent, and pollen should be collected from varieties with special ornamental value in flower color and flower type. Pollen can be refrigerated in an ice bottle for long-distance transport. Pollination is best carried out when the stigma secretes mucus. To increase the success rate, pollination should be repeated 2-3 times. Because the self-pollination rate is very low, it is not necessary to emasculate in advance, and in cold climates without insect interference, bagging may also be unnecessary.

  After seeds are sown, deciduous rhododendrons bloom after 3 years. They must be screened, then after another 2-3 years of cultivation, when traits are stable, screened again; those that meet ideals are only a few percent. Hybridization, screening, and cultivation are long-term work. Domestically, in terms of horticultural varieties, the new varieties obtained by hybridization already number in the hundreds, and flower colors and flower types are very rich. But the growth and development process of evergreen rhododendrons is longer, and hybridization and breeding work has just begun. Horticultural varieties themselves are complexes of multiple genes and often show various variations in flower color and flower type. New varieties can also be obtained by utilizing the bud sport phenomenon of branches. Among West azaleas, 'Qingnv', 'Xinhong', 'Fengbei', 'Qiushuibo', etc. were all obtained by bud sport selection. Rhododendrons are excellent bonsai material. They have the advantages of slender branches and leaves, evergreen in all seasons, tolerance to pruning, strong sprouting ability, peculiar roots, few pests and diseases, abundant and colorful flowers, and long life. If techniques such as bending branches, braiding and tying, pruning, and root raising are used, artistic shapes such as straight trunk, curved trunk, double trunk, multiple trunk, forest, connected root, cliff, raised root, and rock attachment can be made into stump bonsai beautiful in form, branches and leaves, and flowers.

  Besides potted ornamental use, hairy azalea, East azalea and summer azalea can all be used for courtyard decoration. From as small as a patio or wall corner with one or several plants dotted in, to as large as around forested hillsides, streamsides and roadsides, and beside lawns and rocks, planted in clumps or patches, they can all form beautiful landscapes. Rhododendrons can also be used to form flower tubes, green barriers and ground cover plants. In late spring they are full of flowers like brocade, in summer dense and verdant, and in autumn and winter they again have colored leaves, so they can be enjoyed in all four seasons.

  In addition, rhododendrons also have edible and medicinal value. The flowers of Yingshanhong are sour and non-toxic and can be eaten raw; the flowers of Rhododendron decorum and Rhododendron crassistylum are still excellent vegetables for the people of central Yunnan; soaking and composting the branches, leaves and flowers of Rhododendron molle can be used as an insecticidal pesticide; Rhododendron dauricum, etc. can be used to make medicine. The bark and leaves of some species are rich in tannins and can be used to extract tannin extract; the wood and root crowns of rhododendrons are fine and tough in texture and can be made into bowls, chopsticks, basins, bowls, tobacco pipes, roots and other daily-use crafts and artworks.

Related knowledge and care management of rhododendrons