What are the types and characteristics of willows?

Willow is the general name of a plant: Salix psammophila. Salix is mostly shrub, sparse tree, without terminal bud, zygotic branch and few stamens, which shows that it is more evolved than Salix.

There are about 520 species of this genus in the world, mainly distributed in temperate regions of the northern hemisphere, followed by cold regions, and few in tropical regions and southern hemisphere. There are 257 species in China, 122 variety and 33 variety. All provinces and regions have production.

The morphological characteristics of Salix are as follows: trees or creeping, cushion-shaped, erect shrubs. The branches are cylindrical and the pith is nearly round. There is no terminal bud, the lateral buds are usually close to the branches, and the bud scales are single. Leaves alternate, sparsely opposite, usually narrow and long, mostly lanceolate, pinnately veined, serrated or entire; Petiole short; Stipules, serrated, usually early, sparsely persistent. _ The catkin inflorescence is erect or obliquely spreading, and the first leaves are open, or open at the same time as the leaves, and the leaves are sparse; Bracts entire, hairy or glabrous, persistent, sparsely caducous; Stamens 2- numerous, filaments free or partially or completely connate; Gland 1-2 (located between inflorescence axis and filament, abdominal gland, near bract, dorsal gland); The pistil consists of 2 carpels, the ovary is sessile or stipitate, the styles are different in length, or missing, single 1 or dehiscent, the stigma 1-2, dehiscent or indehiscent. Capsule 2-valved; The seeds are very small. How dark brown.

Willow is a kind of plant with ecological amplitude, which has wide adaptability to the environment. Like light, wet and cold, it is a medium-sized wet tree species. However, some species are also more drought-tolerant and salt-tolerant, can grow in places with poor ecological conditions, and grow better in plain areas with excellent site conditions. The average life span is 20 ~ 30 years, and a few varieties can reach 100 years or more. The annual growth period is long, germination is early, defoliation is late, and individual varieties in the south.

Willow is suitable for various ecological environments. Willow grows in mountains, plains, sand dunes and polar regions. Mainly distributed in temperate regions of the northern hemisphere. China's North, Northeast and Northwest Plains. Weeping willows spread all over China and were introduced to many countries in Europe, Asia and America. Korean weeping willows, round-headed willows, Bai Liu willows and great white willows are mostly produced in the northeast of China, but also in some countries such as Korea and Japan. Firecracker willow originated in Europe, and then was introduced to the northeast of China. China, Xinjiang, Gansu, Qinghai and Tibet, Iran, Pakistan, northern India, Afghanistan, Russia and Europe. Salix psammophila is produced in the middle and lower reaches of the Yellow River and southern Liaoning Province, as well as Korea and Japan. Yunnan willow is produced in China, Yunnan, Guangxi, Guizhou and Sichuan. Produced in the lower reaches of the Yangtze River in China. Produced in Sichuan Province, China. Cotton willow has been introduced in China, Beijing, Shanghai, Guangzhou and other cities.

Willow gets its name from the working method of willow head wood. Wood is still an indispensable material. In ancient times, tools were simple, so it was very difficult to cut thick trunks, while it was more convenient to cut branches two inches thick. Therefore, the wood used by ancestors was mainly branches two inches thick. In the long-term use, people will find that after cutting off the branches, new branches can grow at the stubble, and the new branches are straight, which is more conducive to use. Among the native tree species in China, the ability of sprouting branches of willow is the most outstanding. Therefore, a willow tree was formed, the crown was cut off at a certain height to promote the germination of new branches, and the branches were cut off every few years for later use. The result of the first wood operation is to keep the trunk so as to continue to use the branches. This is why the willow tree got its name. The word "Liu" has the same pronunciation as the word "Liu", which means "Liu", which means a tree that keeps its trunk for reuse.

Garden value

There are many kinds of willows, which are easy to cross. Hybrid has strong growth potential and adaptability, and it is easy to reproduce asexually. You can choose from natural or artificial hybrid populations and obtain excellent clonal varieties through asexual propagation. In addition, this method can also be used to quickly obtain a large number of high-quality seedlings. Breeding based on ornamental gardens should focus on improving their branches, leaves and tree shapes, and improving their anti-pollution and pruning and shaping abilities.

Willow is one of the main tree species in the park, with beautiful tree shape, early flowering and shady trees in early spring. Such as weeping willows and Korean weeping willows, have slender drooping branches and new willow leaves. All kinds of shrubs and willows are resistant to pruning and can be cultivated into shrubs of various shapes or used as hedges. Willow is the most suitable for waterside greening in garden landscape, such as "Willow" in Hangzhou West Lake and "Taoxi" in Hangzhou. There are still many beautiful willows to be developed, such as those with big leaves, magnolia-like, purple branches, long spikes, red and yellow, red pistils and stigmas, which are also beautiful. In addition, there are more than 20 kinds of alpine willows, which are only 5 ~ 30cm in height, with creeping or upright branches, twisted and deformed, with different shapes, long life and easy survival, and are good materials for making garden bonsai. Commonly used in garden viewing, residential areas, gardens, schools, factories, hillsides, courtyards, roadsides and buildings. When in full bloom, the branches extend in all directions, making the courtyard full of green with high ornamental value; It is an ideal tree species to beautify the courtyard. Strong resistance to air pollution and dust, suitable for moderate growth, especially in ponds or streams.

economic value

Bark contains tannin; Poor material, can be used as utensils and paper raw materials; Catkin can fill chair cushions and pillows; Branches and fibrous roots can dispel wind and remove dampness. There is a cloud in the poem: the willow is dark and the flowers are bright. It shows that willow is extremely easy to survive. The fiber of willow bark can be used as raw material for textile and rope making; Branches can be woven into baskets, baskets, crates and helmets. Wood is white and tough. Can be used as small household appliances and charcoal.

Willow is light, easy to cut, does not deform after drying, and has no special smell, so it can be used as building, box, board and other materials. Wood has high fiber content and is used for papermaking and raw materials; Willow and willow branches are good firewood; Many kinds of wicker can be woven into baskets, boxes, hats and so on. Willow leaves can be used as feed for sheep and horses; Honey source plants; It is a beautiful ornamental tree species.

Environmental governance

Sweden obtains bioenergy by cultivating short willow short forest (hereinafter referred to as short willow short forest). Short willow short forest afforestation is mainly agricultural land, which is used for cogeneration of district heating plants.

While producing bioenergy, willow dwarf forest can also play a role in removing pollutants and managing the environment. Sweden has successfully used willow dwarf forest to treat urban wastewater, landfill leachate, industrial wastewater (such as wastewater from wood storage plants sprayed with logs), sewage sludge and sawdust. , mainly through plant absorption to reduce pollutants and excess nutrients in water and soil, and promote degradation. This process is called phytoremediation.