A willow tree is a tree in the genus Salix, which contains around 400 distinct species of trees and shrubs native to the Northern hemisphere. Willows prefer cool, moist environments, and they are found in both cold and temperate regions of the Northern hemisphere along the banks of rivers and marshes. Willow trees have a number of commercial uses, and the trees are also frequently planted as ornamentals, since some species have quite attractive growth habits.
Several traits are common to all willow trees. As a general rule, their leaves are narrow, and they produce flowers in the form of catkins. The wood of willow trees is famous for being both lightweight and strong, making it a popular material for everything from furniture to cricket bats. Willows are also very promiscuous, hybridizing freely with other trees and growing from both cuttings and aerial roots. This can be a problem when people are attempting to eliminate willows, as is the case in some areas where they are choking out native species.
A willow which has evolved in cooler regions of the world tends to take the form of a creeping shrub, rather than a tree, reflecting a desire to protect itself from severe weather and cold. Willows which develop in warmer regions will be much larger, often with very delicate branches which easily snap off, allowing the tree to propagate itself. Willows with especially narrow leaves are sometimes known as osiers, while wide-leaved willows are called sallows.
One famous willow tree hybrid is the weeping willow, which has long, trailing branches. Weeping willows are associated with sorrow both in their native China and in many parts of Europe. Pussy willows, another well known willow varietal, are famous for producing soft, fuzzy catkins in the spring, and they are often collected and brought into the home to celebrate the beginning of spring.
Willow wood can be used in a wide variety of projects, and the bark has historically been used to make medicines, as it contains salicylic acid, the original aspirin. Because willows grow quickly and establish extensive root systems, they have also historically been used to control erosion. The trees are also quite popular among butterflies, leading some people to plant willows to attract butterflies to their yards and gardens.
Many garden supply stores carry a willow tree selection, and they can order specific varieties, should customers so desire. Before planting a willow tree, it is a good idea to think carefully about placement, as these trees can grow extremely tall, overshadowing the area around them. The willow tree is also deciduous, dropping its leaves during the winter months, and this can create quite a mess to clean up.