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Caragana, most commonly known as Siberian pea shrub, is a genus of shrubs or small trees that are native to the cold, semi-arid regions of Siberia in Russia and the Manchuria region of northeast China. They have also been imported and extensively planted in Canada and the northern portions of the United States as windbreaks and screening hedges. Pea shrub is hardy even in poor soils, fast-growing, and tolerant of extreme cold and drought; it is able to thrive in harsh landscapes where many other trees and shrubs cannot. In addition to helping prevent wind erosion, Caragana also provides wildlife habitat and grazing for livestock, particularly sheep and camels.
This genus includes over 100 species of shrubs and small trees, of which Caragana arborescens is more commonly known Siberian pea shrub or pea tree. 'Walkeri' is one variety of the pea shrub that has a weeping form, which makes it more popular for ornamental and landscaping use. 'Lorbergii,' 'Nana,' and 'Pendula' are some other varieties that are cultivated as ornamental shrubs. When used as an ornamental, the form of the shrub can be altered with selective pruning as it grows.
In general, Caragana grows to a height of 10 to 15 feet (3.1 to 4.6 meters) with a somewhat narrower spread. It has an upright form with multi-stemmed branches and small oval-shaped leaves. The deciduous leaves are a bright green through the spring and summer and turn yellow in the autumn. Small yellow flowers appear in May, which are replaced with elongated seed pods during the summer. The pods turn tan or brown as they ripen, and make a popping sound when they burst open in late summer and autumn.
When planted in rows along the edges of crops, Siberian pea shrub grows rapidly into a dense protective border. It also has a large, branching root system; both of these qualities make Caragana an excellent choice for holding soil in place and reducing wind erosion from fields. Caragana can live up to 50 years, but must be pruned back every three or four years to maintain its thick foliage and screening properties.
In China, Caragana has been used extensively in land reclamation projects. The extensive roots protect against sand erosion, but also help prevent water erosion on hillsides when planted in a terraced pattern. Caragana also has nitrogen fixation properties, and it adds organic matter to the soil in the form of leaf and twig litter. Previously poor soils have been improved by planting and maintaining large groves of pea shrub.
Caragana is also an important source of nutrition for wildlife as well as grazing domesticated herds of sheep, goats, camels, and reindeer. In cold climates, the pea shrub provides foliage and bark through the winter, when prairie grasses are covered with snow. The seeds can also be harvested in fall and fed to livestock through the winter months. The plant itself benefits from the periodic "pruning" provided by grazing animals. Pruning encourages thicker growth the following spring.