Where is the origin of azaleas?

In the natural distribution of rhododendrons in the world, no one can compare with China in terms of species and quantity. China is a treasure house of rhododendron resources in the world! Today, as many as seven or eight cities in Jiangxi, Anhui, Guizhou and other places regard azaleas as provincial flowers and designate them as city flowers, which shows that people love azaleas deeply. Du Juanhua is a big genus, with more than 900 species in the world, distributed in Europe, Asia and North America, among which Asia has the most, with 850 species, of which China has more than 530 species, accounting for 59% of the world's species, especially in Hengduan Mountain area of Yunnan, Tibet and Sichuan provinces, which is the origin and distribution center of rhododendron in the world.

There are many species in Bhutan, Sikkim, Nepal, Myanmar and northern India in the Himalayas, but there are few species in Japan, Korea, Siberia and Caucasus. In addition, there are about 280 species from New Guinea to Malaysia, which is the secondary distribution center of rhododendron. Among them, there are more than 65,438+060 species in New Guinea, more than 65,438+000 species in Indonesia, and 65,438+00 ~ 20 species in Philippines, Vietnam and Malay Peninsula. Because this area is a tropical island mountain with humid climate, the rhododendrons produced are almost epiphytic shrubs, and their seeds have peculiar filiform long tail appendages, forming a special type of tropical mountain. There are only 24 species in North America, 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 are distributed around the North Pole. There is only 1 species in Oceania, which is distributed in Queensland, northern Australia and belongs to tropical alpine type.

Through the investigation and study of modern botanists, the distribution of the flowers of Eucommia ulmoides in China has been basically clear. There are many species in Jiangnan, but few species in Jiangbei. Yunnan is the largest, followed by Tibet and Sichuan. The farther away from this center, the fewer species there are. Xinjiang and Ningxia belong to arid desert areas and have no natural distribution. The species number of rhododendron in each province (region) is as follows: Yunnan 257 species, Tibet 174 species, Sichuan 152 species, Guangxi 75 species, Guangdong 35 species, Guizhou 43 species, Hunan 37 species, Fujian 35 species, Taiwan Province 30 species, Jiangxi 27 species, Hubei 27 species, Zhejiang/KL species. Vertical distribution, the highest altitude is 4500 ~ 5000 meters.

The main producing areas of rhododendrons in China are Hengduan Mountain areas in Yunnan, Tibet and Sichuan provinces. Its intricate topography constitutes a special climate, with uneven rainfall distribution, drought in winter and spring, rainy in summer and autumn, and obvious vertical distribution. 1000 ~ 2000m low valley, with 2000m ~ 2800m of rhododendron camptotheca and rhododendron macrophylla, with cool climate, bright Mao Dujuan, Rhododendron crassipes, Rhododendron yunnanensis and Rhododendron axillaris. The sunny slope of 2800 ~ 4000 meters in the valley is a mixed forest of evergreen broad-leaved trees and broad-leaved trees. On its forest edge or grass slope, it is composed of Rhododendron flavum, Rhododendron glauca, Rhododendron delavayi, Rhododendron pubescens and Rhododendron albiflora. There are the most kinds of rhododendrons here, and the flowering period is from April to July. They are colorful and dazzling, sometimes covering the whole mountain 10 to 20 square kilometers. In the 4000 ~ 4500m zone, there are few trees and shrubs, and the multi-skilled rhododendrons, recumbent rhododendrons and Rhododendrons with the height of 10 ~ 20cm become bedding plants, which breed on gravel graves or flowing stone beaches. There is no rhododendron distribution above 4500 meters. Alpine evergreen rhododendron grows in humid, cold and high-altitude mountainous areas for a long time. The introduction needs to create similar environmental conditions, such as PH5~6, no water on the ground, good air permeability, rich organic matter, covered germination, water spraying and other equipment.

Rhododendron is the representative of deciduous rhododendron, which is the most widely distributed. North to Henan and Shandong, south to the Pearl River Basin, east to Fujian and Taiwan Province Province, west to Sichuan and Yunnan, high mountains, low mountains, sunny slopes, valleys, rocks, forest margins, weeds and shrubs. Bloom in March and April in the south of the Yangtze River is very colorful. Mountain people use this as firewood and cut it down repeatedly, which shows that it has strong adaptability and vitality. Transplantation used to be difficult to live, which was related to not being re-cut. Although the horticultural varieties have been artificially improved, they still reflect the basic habits of the original species of cold and heat resistance, requiring fertile and acidic soil, loose and transparent. Some azaleas have a long life. For example, there are rhododendrons planted in Yunnan for more than 500 years, and there are rhododendrons planted in Wuxi for more than 50 years.

Propagation and culture:

Propagation method: Rhododendron can be propagated by sowing, cutting, grafting, layering and other methods.

1. Rhododendron has high seed setting rate, many seeds, high germination rate, strong plasticity and vitality of seedlings, but it grows slowly, is difficult to cultivate, and its offspring are not necessarily ideal, so seeds are rarely used in production. It can only be used in the following situations: first, it is used to cultivate rootstocks; The second is to obtain new varieties by cross breeding; Third, it needs to be used when introducing excellent wild species.

(1) Seed collection: Small fruits change from green to brown. When the upper part just cracked, the fruit was harvested and dried indoors. After all petals are cracked, the seeds can be harvested and stored in a dry place indoors.

(2) Sowing: pot planting in spring. In shallow pots, wooden boxes or underground seedbeds, crushed sphagnum is used as sowing substrate, and wet sphagnum should be compacted to 3/4 of its original thickness. A layer of loose sphagnum with a thickness of 3mm should be removed from the surface and sprayed with a fine watering can. Because the seeds are small, sowing should be carried out by sowing. After insertion, it is not covered with soil, but covered with glass and a layer of newspaper, and can germinate at 15 ~ 20℃ for 2 ~ 3 weeks.

(3) Management: After germination, the plastic film can be removed, and ventilation can be gradually strengthened to improve the resistance of seedlings. Keep the soil moist. When the seedlings grow to 2-3 true leaves with a height of 1 .5-2.5cm, they can be transplanted1time after autumn, with a spacing of 4-5cm and a height of 3-4-5cm. Pay attention to avoid unfavorable environment such as strong light and strong wind at seedling stage.