Introduction of Rhododendron

The scientific name of Rhododendron simsii & R.spp The aliases are Yingshanhong, Shan Shiliu, Hibiscus amurensis, Hibiscus amurensis, Hibiscus amurensis, etc. It belongs to Ericaceae and Ericaceae, and is one of the top ten famous flowers in China.

among all ornamental flowers and trees, they are both beautiful in flowers and leaves, suitable for ground planting and potted plants, and the most widely used one is azalea. Bai Juyi praised, "If you hold two branches in your hand, it doesn't look like something in the world. This thing in the flower is beauty, and hibiscus and peony are all in Mo Mu." In the natural distribution of rhododendrons in the world, none can match China in terms of variety and quantity. China is a treasure house of rhododendron resources in the world! Today, there are as many as seven or eight cities in Jiangxi, Anhui and Guizhou where rhododendron is the provincial flower and designated as the city flower, which shows people's deep love for rhododendron. Du Juanhua is a big genus, with more than 9 species in the world, distributed in Europe, Asia and North America, with Asia accounting for the most, with 85 species, of which there are more than 53 species in China, accounting for 59% of the world's species, especially in the Hengduan Mountains in Yunnan, Tibet and Sichuan provinces, and it is the origin and distribution center of rhododendrons in the world.

There are many species in Bhutan, Sikkim, Nepal, Myanmar and northern India in the Himalayas, and only a few species in Japan, Korea, Siberia and Caucasus. In addition, there are about 28 species in New Guinea-Malaysia region, which is the secondary distribution center of rhododendron. Among them, there are more than 16 species in New Guinea, more than 1 species in Indonesia, and 1-2 species in the Philippines, Vietnam and Malay Peninsula. Because the area is a tropical island mountain with a humid climate, the rhododendrons produced are almost all epiphytic shrubs, and their seeds have strange filamentous long-tailed appendages, forming a special type of tropical mountains. There are only 24 species in North America, which are distributed along the Atlantic and Pacific coasts of the United States, as well as Canada, Alaska and Greenland. There are only 9 species in Europe, and a few species are distributed around the North Pole. There is only one species in Oceania, which is distributed in Queensland, northern Australia, and belongs to tropical alpine type.

The distribution of Duyang flowers in China has been basically clear through the investigation and study of modern botanists. There are many species in the south of the Yangtze River and few in the north of the Yangtze River. Yunnan is the largest, followed by Tibet, and Sichuan is the third. The farther away from this center, the less species there are. Xinjiang and Ningxia belong to arid and desert areas, and there is no natural distribution. The species numbers of Rhododendron in various provinces (regions) are as follows: 257 species in Yunnan, 174 species in Tibet, 152 species in Sichuan, 75 species in Guangxi, 35 species in Guangdong, 43 species in Guizhou, 37 species in Hunan, 35 species in Fujian, 3 species in Taiwan Province, 27 species in Jiangxi, 27 species in Hubei, 18 species in Zhejiang, 15 species in Gansu, 13 species in Shaanxi, 13 species in Qinghai and An Wei. Vertical distribution, up to 45-5 meters above sea level.

Rhododendrons have different morphological characteristics in different natural environments, and the differences are very wide. There are evergreen Da Qiao trees, small trees, evergreen shrubs and deciduous shrubs. Some of them have thick trunks, which are more than 2 meters high, while others are creeping, cushion-shaped or epiphytic, and the height is only 1-2 cm. The basic form is: the trunk is upright, solitary or clustered; Branches alternate or pseudowhorled.

branches and leaves are hairy or not, and branches, leaves and pedicels are scaly or not; Leaves are multiform, but not strip-shaped, entire, with few serrations, leathery or papery, evergreen, semi-evergreen or deciduous, with fragrance or without; Flowers are terminal, lateral or axillary, with single flowers, few flowers or more than 2 integrated umbels. The leaves bloom first or later, and the corolla is remarkable, funnel-shaped, bell-shaped, radial rod-mortar-shaped, dish-shaped to bowl-shaped or tubular, 4-5-lobed, and 6-1-lobed; Rich and colorful; There are dark spots or light halos in the throat; There are nectaries or no nectaries at the base; Aroma or tasteless; Flower statue cup-shaped, 4-5-lobed, persistent; Stamens 5-1, rarely 1-25, unequal in length, filaments hairy or absent, carrying drugs, apical pores cracked, ovary superior, 5-1 rooms, style and ovary hairy or absent, glands or absent; Cucurbita moschata cracked into 5-1 petals, with many seeds, mostly powdery or chaff-like. All genera of the original species are divided into 5 subgenera and 8 groups, of which 3 groups are divided into 58 subgroups, with species under the group. Namely:

1. Subgenus of Evergreen Scale-free Rhododendron 1. The group of Evergreen Scale-free Rhododendron is divided into 24 subgroups.

2. Subgenus of Rhododendron Evergreen. 1. The Rhododendron Evergreen is divided into 27 subgroups. 2. Rhododendron Bearded Group 3. Rhododendron Vaccinium Group is divided into 7 subgroups.

3. There is only one species in China.

iv. subgenus azalea 1. short calyx group 2. Sect. azalea

v. subgenus Mayflower 1. Sect. Mayflower 2. Sect.

Several kinds of evergreen rhododendrons are introduced below:

Rhododendron Maying: alias Ma Yinghua, Rhododendron Maying, Rhododendron Niuxuehua, Rhododendron Dog Xuehua, Camellia Camellia and Rhododendron densiflora. Evergreen shrubs to trees, the height of the trees is 2-15m, the diameter at breast height is 4cm, the bark is gray-brown, the maggots are thick, and they are irregularly flaked. The leaves are leathery, oblong-lanceolate, and the back is densely covered with gray-white to tan-brown spongy fluff. The flowering period is from February to May, with a terminal spherical umbel with 1-2 flowers. The corolla is bell-shaped, 3.5-5 cm long, fleshy, deep rose red, with 1 stamens and 1 ovaries. The fruit is ripe in October-November. Yunnan, Guizhou, Guangxi and other provinces are also distributed in Myanmar.

Rhododendron yunjin: alias Rhododendron tianmu and Rhododendron yunjin. Evergreen shrub, 2-4 meters high, with stout light green branchlets. The leaves are thick leathery, oblong to oblong oval or obovate, with dark green leaves and light green back, and no hair. Flowering in May, the terminal umbel has 6-12 fragrant flowers. The corolla is funnel-bell-shaped, 4-5cm long, 7-9cm in diameter, pale pink, with 7 lobes, round, and 14 virions. The ovary has 1 cells. Pedicels, flowers and flowers, the base of corolla, ovary and style all have glands. The fruit is ripe in October-November. Many seeds, bran-like. Among the mountain forests in Zhejiang, Anhui, Jiangxi, Fujian, Guangdong, Guangxi, Hunan, Sichuan and other places with an altitude of 6-2 meters, in recent years, Kangzhou, Wuxi, Shanghai and other places have successfully introduced garden planting.

Rhododendron dendrobii: also known as the whole flower of mountain dog. Evergreen Da Qiao Ben, 25 meters high, with a DBH of 6 cm and a maximum base diameter of 3 meters. Bark is light dark brown and flaked; Branchlets stout, covered with light gray felt. Leaves leathery, oblong to oblanceolate, 24-34 cm long, blunt at the top, wide wedge at the base, dark green on the surface and light green on the back. From February to March, a terminal umbel with 24 flowers, a bell-shaped corolla, a length of 5.5-8 cm, a diameter of 6-8 cm, a water red color, 8 lobes, a round shape, 8 nectary sacs at the base, 16 stamens, 16-loculed ovaries and dense tomentose. The fruiting period is October-November. The evergreen broad-leaved monsoon forest in Gaoligongshan Mountain, Tengchong County, Yunnan Province, which is 24-26 meters above sea level, was first collected by the Englishman G Forresst at the head of Tengchong River in 1915. The sawed wood disc with a diameter of 2.6 meters and an annual ring of 28 years is now in the British Museum in London. It was published as a new species in 1926 and has not been found in China for a long time until Professor Feng Guoliu and others re-discovered it in Tengchong in 1983. This is the tallest azalea tree in the world, known as the "King of Du Juan".

Mayflower: alias Rhododendron ovatum and Qingming flower. Evergreen shrub, 2-4 meters high. The leaves are leathery, broadly ovate, 3-3.5 cm long, with a pointed tip and a rounded base. Flowering from March to May, the flower is solitary in the axils of leaves, pink, rose-red, lavender or purple-white, 5-lobed, 3 cm in diameter, pilose throat, 5 stamens and 5 locules in ovary. Fruiting period: August-October. It is found in shady forests or valley bushes on hillsides at an altitude of 5-12m in Jiangsu, Zhejiang, Anhui, Jiangxi, Hubei, Hunan, Fujian, Guangdong, Guangxi, Sichuan and Guizhou provinces. Horticultural Varieties There are about 2 to 3 horticultural varieties widely cultivated in China at present. Because their main lineage is azalea, although they do not shed leaves in winter, they are still classified as deciduous rhododendrons. According to the morphology, characters, parents and sources, it can be divided into four types: Dongjuan, Maojuan, Xijuan and Xiajuan.

dongjuan: that is, dongyuan, because it comes from Japan. Also known as Shiyan, cinnabar Rhododendron, and spring cuckoo. This class includes Dujuan Shiyan and its varieties, and there are many varieties. Its main characteristics are: short stature, l-2 meters high, scattered branches, pale leaves, little shiny hair, blooming in April, dense flowers, the smallest flowers, a general diameter of 2-4 cm, the largest to 6 cm, single petals or sleeve petals formed by calyx petals, few double petals, and various colors. Traditional varieties include' Xintiandi',' Snowy Moon',' Bizhi',' Sunrise', and the reputation of' Four Seasons' that can blossom twice in spring and autumn, etc.

Hairy cuckoo: commonly known as Rhododendron pubescens, Rhododendron macrophylla, Rhododendron vernaculata, etc. This class includes Rhododendron splendens, Rhododendron tomentosa, their varieties and miscellaneous species. They are tall, 2-3 meters in size, strong in growth and adaptability, and can be planted in the open field. They are excellent rootstocks for grafting West cuckoos. Young branches densely covered with brown bristles. The leaves are 1 cm long and rough and hairy. The flowers are large, single, wide and funnel-shaped, with few double petals, and the colors are red, purple, pink, white and compound colors. There are more than 1 varieties, and the most cultivated ones are' Jade Butterfly',' Purple Butterfly',' Ryukyu Red' and' Yuling'.

Xijuan: It was first bred in Holland and Belgium in Western Europe, so it is called Xijuan, which is a cross of Gaoyue Rhododendron, Yingshanhong and Maobai Rhododendron. It is the most beautiful one with the most colors and patterns. Its main characteristics are short and strong, dense crown, delicate habits, fear of sun and freezing. The leaves are thick, dark green, with little hair. The leaves are divided into smooth leaves, pointed leaves, twisted leaves, long leaves and broad leaves. Flowering in April-May, there are various colors, such as monochrome, flying white, edging, red dots, bright spots, sand blasting, brocade spraying, etc. Most of them are double petals, double petals, and few are single petals. The flowers are long and narrow, round, flat, backward, wavy, flying, ruffled and curled, with a diameter of 6-8 cm and a size of more than 1 cm.

Xia Juan: It is native to India and Japan, and Japan is called Gaoyue Rhododendron. Branches come first and bloom at the latest, usually from late May to June, hence the name. The main features are slender branches, dense branches, full and neat crown, about 1 meter high. The leaves are narrow and closely arranged. The flowers are funnel-shaped with a diameter of 6-8 cm, and the colors and petals are as varied as those of Xijuan. The flowers have single petals, compound petals and re-identification, which is a good material for making pile scenes. Traditional varieties include' Changhua',' Dahongpao',' Chenjia Yinhong',' Wubao Lvzhu' and' Zichen Hall'. Among them, there is a small flower in the' Five Treasures and Green Beads' flower, which is in the form of a pavilion, which is the highest double petal among rhododendrons.

The main producing areas of Rhododendron in China are Hengduan Mountains in Yunnan, Tibet and Sichuan provinces. Its intricate topography and ground potential constitute a special climate, with extremely uneven rainfall distribution, drought in winter and spring, rainy in summer and autumn, and obvious vertical distribution. In the 1-2-meter low valley, there are Rhododendron acutum and Rhododendron macrophyllum at 2-28 meters, and the climate is warm and cool, including Mao Dujuan, Rhododendron crassipes, Rhododendron Yunnan and Rhododendron axillaris. 28-4m gully sunny slope is a mixed forest with evergreen broad-leaved trees and broad-leaved trees. On its forest edge or grass slope, Rhododendron davidii, Rhododendron dauricum, Rhododendron pilosum and Rhododendron praecox form an inseparable rhododendron forest or harbor cluster. Here, Rhododendron davidiana has the most kinds of flowers, which bloom from April to July and are colorful and splendid, sometimes covering the whole mountain for 1-2 square kilometers. There is no rhododendron distribution above 45 meters. Alpine evergreen rhododendron grows in humid, cold and high-altitude mountainous areas for a long time. The introduction must create similar environmental conditions, such as no water on the ground, soil pH of 5-6, good permeability, organic quality, and equipment such as covering germination, spraying water and cooling.

Rhododendron rhododendron is the representative of deciduous rhododendron, which is most widely distributed, reaching Henan and Shandong in the north, Pearl River Basin in the south, Fujian and Taiwan Province in the east, Sichuan and Yunnan-Guizhou in the west, with traces of high mountains, low hills, sunny slopes of shady slopes, ravines and rocks, forest edges and weeds and shrubs. Jiangnan blooms in March-April, and it is full of purples. Mountain people use this as firewood, and they cut it repeatedly, which shows its strong adaptability and vitality. In the past, transplantation was difficult to live, which was related to not being re-cut. Although the horticultural varieties have been artificially improved, they still reflect the basic habit of cold resistance and heat resistance of the original species, and require fertile and acidic soil, loose and transparent. Some rhododendrons have a long life span. For example, there are rhododendrons in Yunnan that have been planted for more than 5 years, and Rhododendrons in Wuxi that have been planted in the open for more than 5 years.

1. Sowing: Rhododendron has high fruiting clusters, many seeds and high germination rate. A large number of offspring can be obtained by using seeds, and the seedlings have strong plasticity and vitality, which is an important means of introduction and breeding.

1. seed collection: when the cucurbits are green-brown or yellow-brown, they can be harvested, dried indoors, shaken out when they crack, and stored indoors in a dry place. Sow in the next spring.

2. sowing: use shallow pots, wooden boxes or underground beds to lay the bottom with coarse-grained soil with good drainage, and use orchid mud or rotten leaf soil for the surface layer of 2 cm (all need disinfection). After the seeds are removed evenly, cover them with a thin layer of fine soil. Or spread .5-1 cm of broken water moss on the orchid mud, and sow the seeds directly into the water moss without covering. Then the basin soil is wetted by water, covered with film or glass plate, and placed in the shade.

3. management: before emergence, keep the soil moist. Generally, at 15-2℃, the seedlings emerge in about 2 days, and the germination rate is 75-85%. After that, the mulch can be removed, and ventilation should be paid attention to to improve the resistance of seedlings. When it is dry, spray it with a sewing nozzle, and don't wash down the seedlings.

4. Seeding: Rhododendron deciduous grows rapidly, and can be transplanted for the first time when 2-3 real leaves grow, with the spacing of 2-3 cm. After autumn, it grows to 2-3 cm high, and then it is dug up again and transplanted in a 3-inch pot, with 3 plants in one pot. In the second year, depending on the growth situation, flowers can be seen in 3-4 years. The evergreen rhododendron was transplanted for the first time after autumn, and transplanted again in the following autumn. Strong light, heavy rain and strong wind should be avoided at seedling stage, and the soil should not be too wet. Water should still be sprayed.

second, cutting: it is the most widely used method, with the advantages of simple operation, high survival rate, rapid growth and stable characters.

1. Cutting: Take the tender and lignified branches of the year, break them off with the heel, smooth the hairy heads, cut off the lower leaves, and leave 4-5 leaves at the top. If the branches are too long, the top tips can be cut off. If you can't insert it as you pick it, you can wrap the base with wet cloth or moss, cover it with plastic film, and put it in the shade for several days.

2. time: cutting before the rainy season in the south of the Yangtze River has the highest survival rate, with Xijuan from late May to early June, Maojuan from early June to mid-June, Dongjuan and Xiajuan from mid-to late June. At this time, the cuttings are tender and moderate, the weather is warm and humid, and the survival rate is over 9%.

3. method: a small amount of pot inserts can be used, and a large number of bed inserts can be used. The medium can be orchid mud, Huangshan soil, river sand or hard rock, pearl rock, etc.