How to Propagate Rhododendron pulchrum? A Complete Guide to Propagation Key Points
Rhododendron pulchrum is suitable for planting in mass beds; when in bloom, its ornamental value increases greatly and it is very beautiful. In addition, Rhododendron pulchrum is also very suitable for planting beside rocks, by pond edges, and along lawn borders. Nowadays, more and more flower enthusiasts grow Rhododendron pulchrum in pots in hotels, homes, and other places to improve the indoor environment.
Rhododendron pulchrum is suitable for planting in mass beds; when in bloom, its ornamental value increases greatly and it is very beautiful. In addition, Rhododendron pulchrum is also very suitable for planting beside rocks, by pond edges, and along lawn borders. Nowadays, more and more flower enthusiasts grow Rhododendron pulchrum in pots in hotels, homes, and other places to improve the indoor environment.
Rhododendron pulchrum
Cutting propagation method: Carry out during the plum rain season. Select semi-mature young shoots, 12-15 cm long, remove the 2-3 leaves at the base, keep the terminal leaves and cut them in half. Treat the cuttings with a 0.8% indolebutyric acid solution for 2-3 seconds, insert into a sand bed, maintain room temperature at 15-18°C, and roots will form 50-60 days after insertion.
Rhododendron pulchrum belongs to the order Ericales (Rhododendron detail introduction), family Ericaceae, a semi-evergreen shrub. It prefers a cool, moist environment with ample sunlight. It is cold-hardy, fears heat, tolerates partial shade, and cannot withstand prolonged intense direct sunlight. The optimal growth temperature is 15-28°C, and in winter it can withstand low temperatures of -8°C. The soil should ideally be fertile, loose, well-drained acidic sandy loam.
Introduction to Rhododendron and Key Care Points
Rhododendron
Scientific name: Rhododendron
Family and genus: Ericaceae, Rhododendron genus
Origin and distribution: Mainly distributed in Asia, with the most in China. One of China's top ten traditional famous flowers.
Key care points: Rhododendrons grown as pot flowers mainly fall into two categories: Mao azaleas and Western azaleas (Belgian azaleas). Mao azaleas include Rhododendron pulchrum (R. pulchrum) and Rhododendron mucronatum (R. mucronatum) and their varieties and hybrids. The plants are tall and are often used as grafting rootstock for Western azaleas. Western azaleas were bred in the Netherlands and Belgium by hybridizing Rhododendron simsii, Rhododendron mucronatum, and others; the plants are short and sturdy, and they have the most varied and most beautiful flower colors and flower forms. Plant in small pots using slightly acidic leaf mold or peat soil; fertilize once every 1-2 weeks during the growing season; water with soft water, keep the potting soil moist, and avoid waterlogging. It prefers partial shade; in summer provide about 50% shade; the overwintering temperature is 0-5°C.
Propagation: Cuttings.
Light: Requires light, slightly shade-tolerant (partial shade).
Water: Grows in moist environments with high soil water content. (Soft water)
Temperature: Strong cold resistance, can withstand low temperatures below -10°C.
Humidity: Prefers moisture, relative humidity above 60%, generally 70%-90%.
Rhododendron rhododendron Rhododendron illustrated guide: How to grow Rhododendron / How to propagate Rhododendron
Rhododendron ProfileRhododendron rhododendron
Rhododendron cultivation methods and precautions Introduction to Rhododendron
One of China's top ten famous flowers. Among all ornamental flowering trees and shrubs, it can be called beautiful in both flower and leaf, suitable for both ground planting and pot cultivation, and has a very wide range of uses. Bai Juyi praised it: "Idly pluck two branches and hold them in hand, look closely and they seem not of this world; among flowers this is Xi Shi, while hibiscus and peony are all Mo Mu." In the natural distribution of rhododendrons in the world, China is renowned for having the most species and the greatest numbers of rhododendrons; China is a treasure house of rhododendron resources. Currently Jiangxi, Anhui, and Guizhou have rhododendron as their provincial flower, and even more cities have designated it as their city flower.
Thorny shrub or small tree, 1-10 m tall, sometimes climbing, much branched, branches stout, young branches sometimes sparsely hairy. Thorns axillary, opposite, stout, 1-5 cm long. Leaves papery or nearly leathery, opposite or clustered on suppressed lateral short shoots, obovate or oblong-obovate, rarely ovate to spatulate, 1.8-11.5 cm long, 1-5.7 cm wide, apex obtuse or shortly pointed, base cuneate or decurrent, both surfaces glabrous or with strigose hairs, or with sparse stiff hairs along the midvein and lateral veins, vein axils on the lower surface often with short tufted hairs, margins often with short ciliate hairs, lateral veins slender, 4-7 pairs, slightly raised below, flat above, petiole 2-8 mm long, sparsely pubescent or glabrous; stipules membranous, ovate, apex aristate, 3-4 mm long, deciduous.
Flowers solitary or 2-3 clustered at the top of leafy, suppressed lateral short shoots, pedicel 2-5 mm long, covered with brownish long soft hairs; calyx tube campanulate or ovate, 3.5-7 mm long, 4-5.5 mm wide, outside covered with brownish long soft hairs, limb slightly enlarged, apex 5-lobed, lobes broadly elliptic, apex pointed, 5-8 mm long, 3-6 mm wide, with 3 veins, outside covered with brownish long soft hairs, inside covered with short stiff hairs; corolla initially white, later becoming pale yellow, campanulate, outside densely covered with silky hairs, corolla tube relatively broad, about 5 mm long, throat with sparse long soft hairs, corolla lobes 5, ovate or ovate-oblong, 6-10 mm long, about 5.5 mm wide, spreading, apex rounded; anthers linear-oblong, exserted, about 3 mm long; ovary 2-locular, each locule with many ovules, style about 4 mm long, stigma fusiform, apex 2-cleft, about 2 mm long. Berry large, spherical, 2-4 cm in diameter, glabrous or sparsely pubescent, crowned with persistent calyx lobes, pericarp often thick, seeds numerous. Flowering period March-June, fruiting period May to January of the following year.
Man Shan Hong is the leaf of Rhododendron dauricum, a plant in the Ericaceae family. It is pungent and bitter in taste, cold in nature, and slightly toxic. It enters the lung meridian. It has the effects of relieving cough and eliminating phlegm. It mainly treats acute and chronic bronchitis.
Main components: Leaves contain flavonoids: hyperoside, isohyperoside, farrerol, 8-demethylfarrerol, kaempferol, quercetin, myricetin, azaleatin, dihydroquercetin, gossypetin; coumarins: scopoletin, umbelliferone; phenolic acids: vanillic acid, p-hydroxy-benzoic acid, gallic acid, protocatechuic acid, syringic acid, rhododendrol, etc., as well as hydroquinone and trace amounts of andromedotoxin.
It also contains volatile oil, including germacrone, juniper camphor, menthol, α-, β-, and γ-eudesmol, and 4-phenyl-butan-2-one. In addition, using gas chromatography-mass spectrometry-computer coupling and chromatographic retention index as two qualitative methods, 24 components were identified from the volatile oil, among which the main components are cis-4,11,11-trimethyl-8-methylenebicyclo[7,2,0]-undeca-4-ene, humulene, γ-selinene, γ-elemene, germacrone, and juniper camphor.
Morphological Characteristics of Rhododendron
The Rhododendron genus has many species and varied forms. They range from large trees (up to more than 20 m tall) to small shrubs (only 10 cm-20 cm tall), with trunks erect or prostrate, and branches alternate or whorled. They are distributed in Europe, Asia, and North America, with the most in Asia. Its difference from Western azaleas is that it is relatively shorter and smaller, and its flower form is relatively smaller.
The leaves are mostly rolled back into tubular shapes, and some are crumpled and broken. Complete leaves, when flattened, are oblong-elliptic or long obovate, 2-7.5 cm long, 1-3 cm wide, apex obtuse, base nearly rounded or broadly cuneate, margin entire, upper surface dark green to brownish green, scattered with pale yellow glandular scales, lower surface grayish green, with very many glandular scales, midvein raised on the lower surface, lateral veins 4-6 pairs. Petiole 3-10 mm long. Nearly leathery. Odor aromatic and distinctive, taste slightly bitter and mildly pungent.
Ecological Habits of Rhododendron
In China, it is distributed in all northern and southern provinces and regions except **, with the most species in Yunnan, Tibet, and Sichuan, which is the world distribution center of the Rhododendron genus. The Rhododendron genus has many species and great differences in habits, but most species are produced in high-altitude areas, prefer cool, moist climates, and dislike intense heat and dryness. They require acidic soil rich in humus, loose, moist, and with a pH value between 5.5 and 6.5. Some species and horticultural varieties have strong adaptability, tolerate drought and poor soil, and can also grow in soil with a pH value between 7 and 8. However, they grow poorly in heavy or poorly aerated soil. Rhododendrons have certain light requirements but cannot tolerate exposure to the sun; in summer and autumn, they should be shaded from the scorching sun by deciduous trees or shade frames, and the ground should often be sprayed with water. Rhododendrons generally flush shoots in spring and autumn, mainly in spring. The most suitable growth temperature is 15-20°C; when the temperature exceeds 30°C or falls below 5°C, growth stops. In winter there is a short dormant period, after which, as the temperature rises, the flower buds gradually swell; generally, open-field cultivation blooms in March-May, while in high-altitude areas blooming is delayed until July-August. In the north, they are cultivated in greenhouses and can bloom in January-February. Rhododendrons tolerate pruning, and latent buds sprout very easily after being stimulated, which can be used to control tree shape and rejuvenate the plant. Generally, pruning is carried out before May; the new shoots produced can all form flower buds in the same year, while pruning too late affects flowering. Generally, new shoots that sprout around the Beginning of Autumn can still lignify. If new shoots form too late, they are prone to frost damage in winter. They are evergreen or deciduous shrubs.
Distribution Areas of Rhododendron
Rhododendron is a large genus, with about 900 species worldwide, distributed in Europe, Asia, and North America, mainly produced in East Asia and Southeast Asia, and not produced in Africa or South America. There are 850 species, of which China has more than 530 species, accounting for 59% of the world total, especially concentrated in the Hengduan Mountains area of the three provinces and regions of Yunnan, Tibet, and Sichuan, which is the birthplace and distribution center of the world's rhododendrons. In the Himalayan range of Bhutan, Sikkim, Nepal, Myanmar, and northern India, there are also relatively many species; Japan, Korea, Soviet Siberia, and the Caucasus have only a few species.
At the entrance of Longyuan Village, Tangkou Township, Pingnan County, Ningde City, Fujian Province, there is a tree over 3 m tall, with a crown diameter of 5 m, seven branches growing in a clump, moss covering the ridged trunk, and a tree age of more than 400 years. It has no flowers only in July each year, and flowers can be seen at all other times; the flower color is bright red. According to expert verification, it is a variety of Rhododendron pulchrum and is very precious. Similar rhododendrons have also been found on the mountains at Jiufeng Temple in Xiling Township, Baolin Temple in Tianping Mountain, and Liugongyan Scenic Area.
The ten-thousand-mu rhododendron fields on Yunwu Mountain in Huangpi District, Wuhan City, have bloomed, with rhododendrons blooming in brilliant colors all over the mountains and plains. Wuhan City specially launched a Wuhan flower-viewing map for the convenience of tourists. The Fourth Wuhan Mulan Rhododendron Festival was held in the Yunwu Mountain Scenic Area of Huangpi. At the opening ceremony, the Huangpi District Tourism Bureau signed a cooperation agreement with the provincial passenger transport company for the "Wuhan to Mulan Eight Scenic Spots Tourist Shuttle," signed an agreement with Guangzhou for "Ten Thousand Cantonese Touring Huangpi," and signed an agreement with the Huangshi City Tourism Bureau for "Huangshi People Touring Huangpi." The rhododendrons on Yunwu Mountain are mainly Rhododendron simsii, and there are also 9 varieties including Rhododendron mucronatum, Rhododendron pulchrum, Rhododendron fortunei, and Rhododendron rubiginosum. The chairman of the scenic area introduced that due to differences in altitude, even on the same mountain, the peak blooming period of rhododendrons occurs at different times, so the flower-viewing period runs from late March to early May.
At the border between Qianxi County and Dafang County in western Guizhou, there is a place called "Baili Rhododendron," which is a stretch of natural wild rhododendron forest extending for 50 kilometers, and is thus called "the Earth's colored ribbon, the world's garden, the hometown of Suoma" (Suoma is the name for rhododendron in the Yi language). The rhododendrons in this forest account for 4 of the world's 5 subgenera, and the varieties are also extremely numerous. The flower area in Dafang County is praised as the "Rhododendron Kingdom" and "Heart of the Flower Sea," while Qianxi County is even praised as the "Capital of Rhododendrons." The Baili Rhododendron Management Committee has also increased tourism development efforts, focusing on creating tourism resources that combine Yi culture and rhododendron culture, attracting many visitors every year from late March to mid-April.
Macheng in Hubei has 1 million mu of ancient rhododendrons, including the 100,000-mu primitive ancient rhododendron community in Guifeng Mountain Scenic Area. According to expert verification, its size, age, preservation, density, and beauty of flower color can be called unsurpassed in central China, and it is the largest primitive ancient rhododendron community discovered in China so far. Among them, the "Rhododendron King" in Guifeng Mountain is more than 300 years old, with 56 secondary branches, each branch stem between 6 cm and 10 cm, a crown diameter of 6 m, and a coverage area of 35 sq m. The ancient rhododendron community of Guifeng Mountain was included in the Shanghai Great World Guinness Records on April 16, 2009, for its large area, long age, high density, good preservation, and beautiful flower color.
Rhododendron is produced in Taiwan, China, Guangdong, Hong Kong, China, Macao, China, Guangxi, Hainan, and Menghai, Pu'er, Gengma, Jinghong, Hekou, and Simao in Yunnan; it grows in forests or thickets in open fields, hills, mountain slopes, and valley streams at altitudes of 30-1600 m. Abroad, it is distributed in Indonesia, Malaysia, Vietnam, Laos, Cambodia, Thailand, Myanmar, Bangladesh, Nepal, Sikkim, India, Pakistan, Sri Lanka, and the tropical regions of eastern Africa. The type specimen was collected from Macao.
Variety Classification of Rhododendron
(1) The 5 subgenera of Rhododendron: 1. Subgenus Hymenanthes (evergreen scaleless rhododendrons); 2. Subgenus Rhododendron (evergreen scaly rhododendrons); 3. Subgenus Pentanthera (sheep poisonous rhododendrons); 4. Subgenus Tsutsusi (Rhododendron simsii); 5. Subgenus Azaleastrum (ma yin flower).
(2) The 58 subsections of Rhododendron:
1. Classification of the evergreen scaleless rhododendron subgenus: the evergreen scaleless rhododendron group is divided into 24 subsections (omitted);
2. Classification of the evergreen scaly rhododendron subgenus: the evergreen scaleless rhododendron group is divided into 27 subsections (omitted), the bearded rhododendron group, and the bilberry rhododendron group is divided into 7 subsections (omitted);
3. Classification of the sheep poisonous rhododendron subgenus: China has only 1 species;
4. Classification of the Rhododendron simsii subgenus: short-calyx group, Rhododendron simsii group;
5. Classification of the ma yin flower subgenus: ma yin flower group, long-stamen rhododendron group.
Under natural cultivation conditions, spring rhododendrons mostly bloom from April to May; summer rhododendrons bloom from May to June; spring-summer rhododendrons bloom between spring and summer rhododendrons; the flowering period can last more than one month.
Commonly cultivated species in China include: Mao azalea, summer azalea, Western azalea, Eastern azalea, spring azalea, sheep poisonous rhododendron, Rhododendron mucronulatum, ma yin flower, and cloud silver rhododendron.
The Rhododendron genus has about 900 species, with about 850 species produced in Asia. Among them, China has about 530 species, distributed in all northern and southern subregions except **. New Guinea and Malaysia have about 280 species, almost all epiphytic. In addition, North America has 24 species, Europe has 9 species, and Oceania has 1 species. The Rhododendron genus has many species and great differences, including evergreen large trees, small trees, evergreen shrubs, and deciduous shrubs.
Rhododendrons are divided into two major categories: deciduous and evergreen. Deciduous types have small leaves, while evergreen types have large leaves. They prefer cool, moist conditions, tolerate cold, and mostly grow on mountain slopes, alpine meadows, forest edges, stone walls, and swamps at altitudes of 1000-1400 m.
Common Species
Rhododendron decorum, Daguan rhododendron, Rhododendron delavayi, Yunnan rhododendron, long-stamen rhododendron, concave-leaf rhododendron, white-flowered rhododendron
Guangzhu charming rhododendron, clustered-flower rhododendron, many-flowered rhododendron, sheep poisonous rhododendron, Xichang rhododendron, Wenke rhododendron, rhododendron
Rhododendron delavayi, charming rhododendron, floriferous rhododendron, dewdrop rhododendron, rusty-leaf rhododendron, Yunnan rhododendron, rhododendron, Rhododendron decorum
Rare Species
White-flowered rhododendron, sheep poisonous rhododendron, glandular-flowered rhododendron
Medicinal or Dietary Therapeutic Value of Rhododendron
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Ultimate flower-protecting mission: Love yourself, start from reality, and strictly follow medical advice. For illness, do not be careless, do not delay, do not give up hope, face it bravely, use love to warm the silent world, and use your heart to care for the flower field within.
Beauty Benefits
Rhododendron has antibacterial and anti-inflammatory effects, among which syringic acid, vanillic acid, and anisic acid all have antibacterial effects and have a good eliminating effect on Cutibacterium acnes caused by acne; the anti-inflammatory effect of its farrerol is equivalent to injected salicylic acid.
Pharmacological Effects
1. Antitussive, antiasthmatic, and expectorant effects: In mice, oral administration of 5 mg germacrone has an antitussive effect equivalent to 2 mg codeine; intraperitoneal germacrone has an effect against histamine-induced bronchospasm in guinea pigs. Farrerol is the main active ingredient of Man Shan Hong in treating bronchitis; among the therapeutic effects on individual symptoms, the effective rate for expectoration is the highest, followed by cough suppression, and antiasthmatic effect is relatively poor. After injecting a small amount of ink into the rabbit trachea, the movement speed was observed in vivo to determine the speed of tracheal ciliary transport of mucus; after intraperitoneal farrerol, the transport speed was significantly accelerated, consistent with the clinical conclusion of expectoration.
2. Anti-inflammatory and antibacterial effects: The guaiazulene contained in this product has anti-inflammatory and uterine-stimulating effects and can be used as an anti-inflammatory agent. Farrerol has antibacterial activity against Staphylococcus aureus, MIC 25 ug/ml. Syringic acid and vanillic acid also have antibacterial and antifungal effects, and anisic acid also has antiseptic and antibacterial effects.
3. Hypotensive and diuretic effects: Andromedotoxin has a hypotensive effect when given intravenously to anesthetized cats. Although avicularin has a hypotensive effect on anesthetized dogs, the duration is very short and rapid tolerance is easily produced. Avicularin at 0.5 mg/kg iv has a diuretic effect on anesthetized dogs, and the effect increases with dose. In rat experiments, whether by oral administration or intraperitoneal injection of 34 mg/kg, a significant diuretic effect can be produced; the strength of the effect is not as great as aminophylline, but its toxicity is only 1/4 that of aminophylline, so its therapeutic index is relatively large.
4. Analgesic effect: Andromedotoxin has a certain analgesic effect, with a minimum analgesic index of 8.60. Hyoscyamine can greatly enhance its analgesic effect without significantly affecting toxicity. Atropine can slightly enhance the analgesic effect of this product. In addition, andromedotoxin has weak cytotoxic activity, with an ED50 of 60 ug/ml, and relatively high in vivo toxicity.
5. Central inhibitory effect: Syringic acid has sedative and local anesthetic effects, and its effects have a dose-dependent relationship.
6. Effect on tissue respiration: Farrerol can inhibit rat trachea-lung tissue respiration in vitro, reducing oxygen consumption by about 26.4%, mainly acting on the pyridine nucleotide enzyme system.
Edible Value
Sweet in taste, warm in nature, can lower blood lipids, lower cholesterol, nourish and beautify the skin; long-term drinking can make the skin delicate and the complexion rosy; it can lower blood lipids, lower cholesterol, reduce inflammation, nourish and beautify the skin, beautify and harmonize the blood, regulate menstruation, dispel wind-dampness, and treat irregular menstruation. It has the effects of clearing heat and detoxifying, beautifying and protecting the skin, harmonizing the blood, regulating menstruation, dispelling wind-dampness, and treating rheumatic pain. Azelaic acid can be extracted from rhododendron to make cosmetics, with certain beauty effects. The roots, leaves, and flowers of rhododendron are used as medicine and have the effects of harmonizing the blood and regulating menstruation, reducing swelling, and stopping bleeding; the flowers and leaves used externally and the roots can treat internal injuries, rheumatism, and other conditions. It can also mainly treat severe wind-phlegm pain, wind-damp arthralgia, and wind-toothache. Rhododendron has a certain toxicity; please use it under expert guidance.
Cultivation Techniques of Rhododendron Rhododendron
Also known as Ying Shan Hong, generally referring to various red rhododendrons, describing its brilliant red splendor that reddens the mountains. In fact, rhododendrons are not only red; in current plant taxonomy, "Ying Shan Hong" is only used as one type (including many cultivated varieties). Yunnan Province alone and Macheng City in Hubei have as many as nearly 300 species. China is the native place of rhododendrons, and Macheng is its distribution center.
Ying Shan Hong
It is a common type of rhododendron, named because when it blooms it reddens the whole mountain. In Longlin, Macheng City, Hubei Province, and in mountainous areas above 500 m altitude such as Xijiang, Fenghuang Mountain, Zhuangkou, and Lanshan in Huichang County, Ganzhou City, Jiangxi Province, it is distributed. Ying Shan Hong has long been known as the "king of woody flowers"; writers and scholars in China and abroad, ancient and modern, have written many beautiful essays and poems praising Ying Shan Hong, such as a poem by Yang Wanli of the Song Dynasty: "Why must one go to famous gardens to see the spring breeze? All the mountain flowers along the way do not fail you. Day after day the Jin River presents a brocade-like scene; the clear stream reflects Ying Shan Hong upside down." This praises the plain and tenacious vitality of Ying Shan Hong.
Wild rhododendrons are mostly shrubs and small trees 1-2 m tall; there are also creeping rhododendrons and purple-backed rhododendrons only a few centimeters tall and prostrate on rocky ground, as well as large tree rhododendrons and giant rhododendrons several zhang tall with tens of thousands of flowers. The top of the rhododendron forms an umbel-like inflorescence, composed of several campanulate or funnel-shaped flowers, just like a full hydrangea. The leaves are mostly leathery, as large as loquat leaves, as small as fingernails; there is even a species called Tujian rhododendron whose leaves are as long as more than 70 cm and more than 20 cm wide; the fruit is a capsule, and the seeds are as fine as dust, so sowing requires careful management before seedlings can emerge.
In Yunnan, rhododendrons grow at altitudes of 800 m to 4500 m in high mountains, mid-mountains, low hills, and fields, with the richest variety in the high mountains of western Yunnan. Especially in high mountain cold and humid zones. Many evergreen rhododendrons such as Rhododendron wardii, Rhododendron nivilis, clustered-flower rhododendron, and broad-campanulate rhododendron, in various colors, often form dense rhododendron thickets and pure forests, even creating the spectacle of a continuous "sea of flowers" of rhododendrons for 10-20 kilometers. The flowering period of rhododendrons varies with climate and species: in warm and hot low mountain zones they mostly bloom from February to March, in cool mid-mountain zones they mostly bloom from April to June, and in cold high mountain zones they mostly bloom from July to August. Because of their many species, wide distribution, and complex and diverse ecological environments, the posture and elegance of rhododendrons are also diverse: some have sparse branches and leaves, some have a hundred branches; some are lush and upright, some are twisted like dragons, vigorous and antique. Their flower colors are even more colorful and varied: deep red like fire, golden brilliant, crystal blue like treasure, or with spots, or with stripes and patches, pink, magenta, orange-yellow, light purple, yellow with red, red with white, white with green, truly ever-changing and full of wonders. Some are heavily made up and brightly dressed, some are lightly clothed in white, some have red lips and white teeth, some are fragrant and refreshing, truly each with its own charm and countless graceful postures.
Because of the important value of rhododendrons in landscaping, China's rich rhododendron resources have long been coveted by Western countries. As early as the early 19th century, they sent people to Yunnan many times at great expense to collect specimens and seeds. Many of the several hundred rhododendrons now boasted by the Royal Botanic Gardens in Britain were mostly collected and cultivated from Yunnan, and have long since grown into forests; when the flower buds are in full bloom, British men and women come and go in crowds, lingering and forgetting to return.
Flowering Period Control
If you want flowers during the Spring Festival, you can move the potted plant to a sunny place in a 20°C greenhouse in January or 20 days before the Spring Festival, with other management as normal, and flowers can be viewed during the Spring Festival. If you want flowers on "May 1st," you can move the pot before early spring budding to an indoor cold storage below 5°C, move it to a sunny place in a 20°C greenhouse on April 10, move it outdoors on April 20, and flowers can be seen on "May 1st." Therefore, temperature can regulate the flowering period, allowing it to bloom at will in all four seasons. In addition, plants pruned immediately after flowering can bloom in late October; if pruned during the peak growing season, the flowering period can be delayed by about 40 days; if pruning is combined with cuttings, the flowering period can be delayed until January-February of the following year. Therefore, pruning at different times also affects how early or late the flowering period is.
Fertilization Techniques
Fertilizing flowers requires mastering the season and achieving timely and appropriate amounts and properly configured concentrations. The root system of rhododendrons is very fine and dense, with a strong ability to absorb water and fertilizer; it likes fertilizer but fears concentrated fertilizer. Ordinary human feces and urine are not suitable; it is suitable to apply alum fertilizer water as a top dressing.
Fertilizing rhododendrons should also be carried out according to different growth stages. From March to May, to promote the growth of branches, leaves, and flower buds, fertilize once a week. June to August is midsummer, when rhododendron growth gradually slows and enters a semi-dormant state; too much fertilizer will not only cause old leaves to fall and new leaves to turn yellow, but also make it prone to pests and diseases, so fertilization should be stopped. In late September, the weather gradually turns cooler and rhododendrons enter autumn growth; apply a 20%-30% phosphorus-containing liquid fertilizer once every 10 days to promote flower bud growth. Generally after October, autumn growth basically stops, so no more fertilizing is needed.
Key Care Points 1. Environmental Conditions
Moisture, acidic soil, and warmth are the environment rhododendrons like most; exposure to the sun, drought and waterlogging, and concentrated fertilizer are the growth environment rhododendrons fear most. For soil culture, rhododendrons must use acidic soil with good aeration, rich humus, and a pH value of 5.5-6.5. In order to maintain the acidity of the rhododendron potting soil, some alum fertilizer water should usually be applied appropriately, or a small amount of ferrous sulfate can be added to the water. When repotting rhododendrons, add an appropriate amount of slow-release fertilizer to the potting soil; this fertilizer is often used in rhododendron horticultural production, saving trouble and keeping things clean, so rhododendrons planted this way have lush leaves and beautiful flowers.
2. Potting Soil Requirements
Rhododendrons like loose, highly permeable, well-drained acidic soil rich in humus, with a pH value of 5.0-6.0. If clay or alkaline soil is used, hardly one in a hundred will survive. Especially summer azaleas and Western azaleas must have mountain soil. Mountain soil also needs to be improved, and generally 3 prepared culture soils are used.
(1) Mix 7 parts mountain soil, 1 part dry sedge scraps, 2 parts dry leaf mold, and 1 part dry fertilizer.
(2) Layer and compost 3 parts mountain surface soil (topsoil), 3 parts horse manure, 3 parts fallen leaves and weeds, and 1 part human feces and urine, and after 1-2 years sieve and set aside for use.
(3) Mix 3 parts mountain soil, 3 parts leaf mold, 4 parts garden soil, and 2 parts sandy soil, and add 50 grams of sesame paste residue and bone meal per pot.
3. Flower Pot Selection
For pots used to cultivate rhododendrons, depending on the purpose, generally two types are chosen: clay pots and purple sand pots. Clay pots have good air and water permeability, which is beneficial to root growth, and flower and tree production units all use this kind of pot for cultivation. Finished rhododendrons, especially those already shaped, are generally planted in beautiful and antique purple sand pots for indoor and outdoor display; purple sand pots are fine in texture, rich in color, and beautiful in shape, which can increase ornamental value. Purple sand pots are not as permeable as clay pots, so when planting, broken tile pieces (old tiles) should be placed around the pot walls to facilitate drainage. The size of the selected pot depends on the age of the plant; generally, 4-6 year old plants use 5-inch pots; 7-10 year old plants use 6-inch pots; 11-15 year old plants use 8-inch pots.
4. Improving Water Quality
For watering rhododendrons, it is best to use rainwater, followed by river water or pond water. If tap water is used, it is advisable to store the water for 1-2 days to let the chlorine evaporate before use. When using it, add 0.2% ferrous sulfate; during the growing season, water once every 7-10 days, and use it regularly to ensure the soil is acidic.
5. Fertilizer and Water Management
Rhododendrons prefer shade and moisture and should not be too dry. During the flowering period, even more water is needed. In winter, rhododendrons have entered the dormant period and do not need much water; generally water once every 4-5 days, preferably around noon on clear and warm days. Specifically, water appropriately depending on the dryness of the potting soil. In March, rhododendrons root and sprout, and water demand increases accordingly. Summer azaleas grow and develop slightly later, so the amount of watering should be less than for spring azaleas. Generally water appropriately once every 2 days in the morning. From April to June, rhododendrons bloom one after another, and branches and leaves also begin to sprout, requiring a relatively large amount of water; generally water once every morning or evening. From July to early September, in the hot and dry season, water once in the morning and once in the evening, but the amount should not be too much, and spray water on the leaves and ground at noon to maintain a moist environment. From mid-September to November, the weather gradually turns cooler, which is an adaptation period for rhododendron growth; to prevent autumn shoots from sprouting and enhance overwintering cold resistance, the amount of watering should be appropriately reduced. Generally water once every other day in the early morning, keeping it moist. Rhododendrons relatively like fertilizer; generally use rotted cake fertilizer, fish meal, broad bean, or Chinese milk vetch, etc., after decomposition mixed with water for irrigation, and avoid using human feces and urine. After leaving the room and before the flower buds open, apply thin fertilizer once every 10 days at a concentration of 15%, for a total of 2-3 times, to promote the old leaves turning green and new roots sprouting. After the flowers fade, in order to promote branch and leaf growth, fertilize 5-6 times from mid-May to early July. If it rains continuously, dry fertilizer can be applied. Before entering the room, before rhododendron growth is about to stop, fertilize 1-2 times.
6. Outdoor Shading
Before leaving the room and before flowering, it is appropriate to give more sunlight; during the flowering period, short-term shading should be carried out at noon, with a light transmittance of 60%; during the plum rain period from June to early July, which is exactly the period when rhododendrons sprout leaves and branches, they should receive as much sunlight as possible. But in strong sunlight, shading should still be provided from 9 a.m. to 4 p.m. to prevent scorching new leaves. From mid-July to early September, shade every day from 8 a.m. to 5 p.m. to prevent scorching sunlight. After September, in the autumn growth period, the shading time can be shortened; generally shade from 10 a.m. to 4 p.m., and after October it is appropriate to give more sunlight. After that, carry out shaping and prune leggy branches, diseased and weak branches, deformed branches, and damaged branches.
7. Shaping and Pruning
Rhododendrons grow relatively slowly, so generally let them grow naturally, and only carry out shaping after flowering, pruning leggy branches, diseased and weak branches, deformed branches, and damaged branches.
8. Cutting Propagation
For rhododendron propagation, five methods can be used: cuttings, grafting, layering, division, and sowing. Among them, the cutting method is the most common and produces the largest number of propagules; layering produces seedlings fastest; grafting propagation is the most complex, and grafting is used only for varieties that are difficult to root by cuttings; sowing is mainly used for breeding varieties.
When using cutting propagation, the cutting pot is best a new shallow clay pot with a 20 cm diameter, because it has good air permeability and is easy for rooting. A culture soil mixed from 20% humus garden soil, 40% horse manure scraps, and 40% river sand can be used as the substrate. The best time for cuttings is spring (May) and autumn (October), when the temperature is between 20-25°C, most suitable for cuttings. When taking cuttings, select vigorous current-year semi-lignified shoot tips as cuttings, use very sharp scissors; cut 6-10 cm with nodes, the cut should be smooth and neat, remove the lower leaves, and keep only 3-4 small leaves at the top. Buy 1 ampoule of vitamin B12 injection, open it, dip the cutting in the medicinal liquid, take it out and let it dry for a while, then it can be inserted. Before inserting, the culture soil in the pot should be sprayed moist with a watering can the day before, but not too much; by the next day it will be just moist, most suitable for cuttings. The insertion depth is 3-4 cm. When inserting, first use chopsticks to poke a hole in the soil, then insert the cutting, press the soil firmly with your hands so that the potting soil and the cutting are fully in contact, and then water thoroughly once. After inserting, it is best to cover the flower pot with a plastic bag and tie the bag opening with a string; open it when watering is needed, and tie it again after watering. The pot with cuttings should be placed in a place without direct sunlight. The potting soil of the cuttings should be sprayed with water every day for 10 days; except on rainy days, spray once on cloudy days, and preferably twice when the climate is dry, but the amount of water sprayed each day should not be too much. After 10 days, still frequently pay attention to keeping the soil moist. Within 4-5 weeks, shade is required, and only after sprouting can it gradually receive some sunlight. Generally it takes about 2 months to root. After that, only shade for 2-3 hours at noon is needed, and the rest of the time it can receive light as it pleases, so as to facilitate photosynthesis and manufacture nutrients on its own.
9. Garden Uses
Rhododendrons have abundant flowers and lush leaves, are gorgeous and varied, have strong sprouting ability, tolerate pruning, and have peculiar root stumps, making them excellent bonsai material. In gardens, they are most suitable for planting in clumps or masses along forest edges, by streams, by pond edges, and beside rocks, and can also be scattered under open forests.
10. Light and Temperature
During the period when rhododendrons sprout leaves and branches, they should receive as much sunlight as possible, but in strong sunlight, shading should still be provided from 9 a.m. to 4 p.m. to prevent scorching new leaves. In summer, shade every day from 8 a.m. to 5 p.m.; after September, the shading time can be shortened; after October, it is appropriate to give more sunlight.
Rhododendrons grow most vigorously at around 20°C; above 30°C they stop growing and enter a dormant state. Long-term exposure below 0°C will freeze them to death. In winter, heat preservation measures must be taken, and a temperature above 15°C is optimal.
Pest and Disease Control of Rhododendron
Disease and pest prevention: For the lantana lace bug (also known as the crown net bug), spray 40% dimethoate 1500x solution during the damage period, once every 7 days, for 3 consecutive times. For the terminal bud leaf roller, the control method mainly relies on manual capture and killing; larvae or pupae can also be sprayed with 40% dimethoate emulsifiable concentrate 2000x solution or dichlorvos 1500x solution.
For red spider mites, 1000x dicofol solution can be used for control. For the lantana lace bug, 1500x dimethoate or dichlorvos can be used. The most common disease is brown spot, which can be controlled with 800x thiophanate or an equal-strength Bordeaux mixture.
Main Pests and Diseases
Red spider mite. Can be sprayed with 40% dimethoate 1500-2000x solution, 58% Fenglei Ji emulsifiable concentrate 1500-2500x solution, etc.
Lantana lace bug (pear lace bug). Can be sprayed with 50% fenitrothion 1000x solution.
Tea bagworm (bag worm, bag moth). Can be sprayed with 90% trichlorfon 2000x solution.
Tea tortrix (leaf-webber). Adults can be trapped and killed with black light lamps; larvae can be sprayed with 20% chlorbenzuron suspension 8000x solution, 20% Duochongwei 2000x solution, etc.
Damping-off. Mostly occurs in seedbeds; when damaging, it causes seedlings to turn brown from the roots to the root collar, later becoming dark brown; in severe cases, the phloem rots, the xylem is exposed, and the roots rot black-brown, causing the aboveground leaves of the seedlings to wither and yellow or even the whole plant to die, but without lodging. The occurrence of this disease is mostly caused by seedlings being planted too densely, poor ventilation, or the seedbed being too wet. To prevent and control this disease, the seedbed must first have good ventilation and light transmission, and shade work must be done well in high-temperature seasons; at the same time, be careful not to water too much and make the soil too wet. If the seedbed soil is first disinfected with 50% captan 500x solution, the effect is even better.
Leaf spot. Rhododendron leaf spot is a common disease. In the early stage of damage, small purple-red spots appear on the leaves; later the center of the lesion becomes grayish white. Small black dots grow on it, causing leaves to fall. This disease occurs 3 times a year on Western azaleas; mid-month, early September, and early October are the peak periods of onset. In winter, after Western azaleas enter indoor maintenance, as long as the temperature is suitable, it will continue to occur. Leaf spot is generally severe during the plum rain and tropical storm seasons. If from May to late August after flowering, 70% thiophanate 1x solution or 20% triadimefon 4000x solution or 50% mancozeb 500x solution is sprayed once every 2 weeks, the development of this disease can be controlled.
Chlorosis. Rhododendron chlorosis often causes its green leaves to evenly fade in green, and the leaf color becomes lighter. First the young leaves lack green, and the mesophyll turns yellow. In severe cases, the leaves turn white, the veins also turn yellow, and necrotic tissues such as scorched brown spots appear at the middle of both sides of the leaf or at the leaf tip, gradually expanding and causing the leaves to fall. The occurrence of this disease is mainly caused by alkaline soil quality and iron deficiency. When this symptom appears, promptly spray the plant with 0.2%-0.5% ferrous sulfate solution; the effect is better than directly applying it to the soil.
Inchworm. Adults can be trapped and killed with black light lamps; larvae can be sprayed with 20% Jusha emulsifiable concentrate 2000x solution, 25% Fengmang emulsifiable concentrate 800-1000x solution, etc.
Brown spot disease. Spray with 70% thiophanate-methyl at 1000 times dilution, or 65% zineb at 600-800 times dilution, etc., once every 5-7 days. Spray 3-5 times consecutively depending on the severity of the disease.
Root rot. Pay attention to strengthening cultivation management; keep the soil moist and loose, and avoid waterlogging. In the early stage of the disease, drench the roots with 12% copper-8-hydroxyquinoline emulsifiable concentrate at 800-1000 times dilution or Lüheng No. 1 at 3000 times dilution, once a week, for 2-3 consecutive drenches. In severe cases, promptly dig the plant out of the soil (for potted plants or bonsai, repot and change the soil promptly), wash off the soil from the roots, and prune off the diseased roots. Then soak the plant roots for 30 minutes in 12% copper abietate emulsifiable concentrate at 600 times dilution, or Lüheng No. 2 at 800 times dilution, or 50% Genfuling wettable powder at 500 times dilution. Then rinse the roots with clean water, and then dip the roots in a thick slurry made by mixing 75% chlorothalonil wettable powder at 1000 times dilution, or 50% carbendazim wettable powder at 800 times dilution, with an appropriate amount of fine red (yellow) soil, and set aside for planting. For field planting, re-dig the holes and loosen the soil (for potted plants and bonsai, replace with loose new potting soil), and drench the soil (potting soil) for disinfection with 50% Genfuling at 600 times dilution, or 50% Shajunwang water-soluble powder at 1000 times dilution, Lüheng No. 1 at 3000 times dilution, 12% copper-8-hydroxyquinoline emulsifiable concentrate at 600 times dilution, etc., and then plant the plant. After planting, spray the foliage once a week with fungicides such as 12% copper abietate emulsifiable concentrate at 1000 times dilution, or 50% Genfuling wettable powder at 800 times dilution, Lüheng No. 2 at 600-800 times dilution, 70% mancozeb wettable powder at 600-800 times dilution, etc. It is best to alternate two or more of them, spraying 3-5 times consecutively.
Leaf gall disease (exobasidium disease). Strengthen cultivation management, ensure environmental ventilation and light penetration, promptly and thoroughly remove diseased leaves and diseased shoot tips when found, and destroy them promptly. Before bud break in spring, spray the plant once with 1 degree Baumé lime-sulfur mixture. During the new leaf emergence period, spray the foliage 2-3 times with 0.5 degree Baumé lime-sulfur mixture or 1% Bordeaux mixture, once every 7-10 days. [3]
Stem bark splitting disease
[Symptoms] The phloem of the lower stem of the rhododendron is damaged and necrotic, the xylem is exposed, and small black spots appear on the diseased area.
[Pathogen] The pathogen is a fungus, Leptosphaeria tritici.
[Occurrence pattern] It generally occurs during the plum rain season. Any factor that causes stem injury will aggravate the disease, such as insect damage, mechanical injury, friction damage, etc.
[Control method] Spray with 50% carbendazim at 500 times dilution, once every 10-15 days. After 2-3 consecutive sprays, the disease can be brought under control.
The flower language of rhododendron
The flower language of rhododendron - forever yours
The flower language of rhododendron - represents the joy of love. It is said that people who like this flower are pure and innocent. The motto of the rhododendron is that when rhododendrons bloom all over the mountains, it is the time when the god of love descends.
Flower language: the joy of love, temperance, temperance of desire
Flower color meaning: the joy of love
White: the joy of being loved
Its flower language is "temperance." The biggest reason is that it blooms only in its own flowering season, even though rhododendrons always give people a lively and bustling feeling. When it is not in flowering season, its dark green leaves are also very suitable for planting in gardens as low walls or barriers.
The cultural background of rhododendron
In 492 AD, Tao Hongjing of the Qi and Liang dynasties recorded in the "Collective Annotations to the Classic of Materia Medica": "Sheep stagger plant; when sheep eat its leaves, they stagger and die, hence the name."
Su Shi of the Northern Song dynasty also mentioned it many times in his poems: "At the time I only thought it was the immortal of Helin, able to leave autumn light and let rhododendrons bloom." In addition, Bai Juyi of the Tang dynasty also wrote "Delight at the Pomegranate Flowers Blooming on the Mountain": "Today the flowers bloom in Zhongzhou, last year's trees on the summit of Mount Lu. I already pitied the roots damaged and newly cut for planting, yet I am still glad the flowers bloom in the same number."
Li Shizhen of the Ming dynasty gave more detailed records of the sheep stagger plant and the azalea in the "Compendium of Materia Medica." Slightly later, the famous geographer Xu Hongzu wrote the book "The Travels of Xu Xiake," which described the rhododendrons of central Yunnan.
Rhododendron pictures