The willows, genus Salix, in the Salicaceae family, are both deciduous trees and shrubs. There are 200 species world wide with more than 70 native to North America. Because the seeds need wet soils to germinate, they are often found along shores and stream banks or in wetlands.
The leaves are narrow, long pointed and finely toothed. The slender twigs are tough and flexible, often shedding. The bark varies from smooth gray brown to scaly and dark, and the roots are tough and can be invasive.
Ancient Egyptians, Greeks, and Native Americans all knew the value of the salicin in the bark of the willow as a remedy for aches and fever. In the 1800s chemists succeeded in isolating this extract which eventually led to the development of a synthetic product which we know as aspirin.
Willow is also important for wildlife as nectar for the honey bees and tender leaves for animals in early spring. Its matted roots provide protection against erosion on stream banks, and its tender twigs can be used in crafts like basketry.
Two native Ohio willows are the Pussy Willow and the Black Willow. The pussy willow grows as a small tree about 20 feet high with multiple trunks. In late winter the catkins are covered with hairs and make a popular feature in floral arrangements.
Proper pruning of the tree can keep pussy willows compact for landscaping (not near waterlines or foundations) as well as make it easier to harvest the pussy willows for design.
The Black or Swamp Willow is a fast growing but short-lived tree that grows along rivers or streams or in swamps. It has a single crooked trunk and grows to a height of 30 to 60 feet. The twigs are light yellow to reddish when young and become gray when mature. The branches spread and are easily broken by the wind.
There are five species of willow in the James H. McBride Arboretum on Firelands BGSU Campus. One is the well known weeping willow, species salix babylonica, named from Babylon though it really is native to China. This tree can reach a height of 30 to 40 feet and has branches which gracefully weep down and touch the water.
It is also called the Golden Willow because of its yellow twigs and autumn color. This tree must be planted in appropriate settings as the roots can clog drains and sewers and fallen twigs and branches can cause litter problems.
While weeping willows have gracefully sweeping branches, there are also willows with twisted stems called corkscrew. Corkscrew willows are a variant of the species salix matsudana, named for a Japanese botanist, Sadahisa Matsuda, and widely cultivated in China.
The branches of this tree grow in a spiral twisting manner. Two cultivars, both grown in the arboretum, “Golden Curls” and “Scarlet Curls” have been selected for resistance to cankers and storm damage.
Golden Curls has distinctive golden stems that are contorted and twisted while the stems of Scarlet Curls are red with the color intensifiying after the first frost. Both are medium sized trees of 30 to 40 feet.
Two scrub species of note in the arboretum are salix alba Britzensis and salix integra “Hakuro-nishiki” Britzensis, also called coral bark willow, grows to a height of 15 to 20 feet. New growth has an orange color which will fade to gray the following year. So this willow can be cut back every year keeping it small and manageable for the landscape as well as providing winter interest in the orange colored stems.
Hakuro-nishiki reaches a height of 6 feet and has branches that explode in all directions and then slightly droop. The young branches are coral to red in the winter while the older branches will be orange and green. This willow, too, benefits from annual pruning to keep variety in the color.
Willows are short lived and can be bothered by pests such as aphids, borers, and caterpillars. The wood is weak and can be damaged by storms, snow, and ice.
The roots can cause problems water systems. But in the right place, such as an arboretum or a shoreline park or creek bank, willows provide variety and interest in the landscape as well as benefit wildlife and prevent erosion.