The Salicaceae or Willow family as it is commonly called is a small world-wide family of perennial woody, flowering plants consisting of mostly trees and some shrubs.
Salicaceae is a relatively small family. According to The Plant List, there are about 54 genera and approximately 1,269 accepted species. In North America, according to the USDA Department of Agriculture there are 2 genera and 202 accepted taxa overall. These genera includes Populus and Salix, and are the cottonwoods, poplars, aspens and willows.
In North America there are 14 (not including hybrids (27)) species of Populus with 23 accepted taxa overall and 130 (not including hybrids (171)) species of Salix with 142 accepted taxa overall.
Salicaceae is native to mostly temperate regions within the northern hemisphere with greatest diversities toward the northern limits. Preferred habitats are riparian areas such as streams, lakes and other moist or wet areas, mostly in higher elevations especially mountains and mountain meadows.
The genus Populus are flowering plants that drop leaves in fall or winter (deciduous). As with the willows, Aspens and Cottonwood trees are also native to most of the Northern Hemisphere.
Characteristics of the Salicaceae family: Plants perennial trees or shrub or sub-shrubs, usually unisexual, sometimes bisexual, usually staminate and pistillate on different plants; dioecious. Stems erect to pendulous, branched. Flowers in catkins either erect or pendulous, flowers in axils of small bracts. The calyx or sepals absent or present and the corolla or petals are usually absent. Flowers emerge well before the leaves break out. Fruitis a small capsule, berry-like (baccate), or drupaceous. The genus Populus has pendant catkins which are wind pollinated and the genus Salix has erect catkins with nectar at the base of the flowers, insect and wind pollinated. Salix trees readily hybridize. Plants are typically fast growing and may produce vegetative cloning and re-sprouting from root shoots, rhizomes and other methods. Species favor temperate and sub-Arctic areas of the Northern Hemisphere and often in wet and mountainous areas.Leaves usually alternate, simple with serrate margins or entire, leaves stipulate or not and deciduous, persistent or marcescent.
Economic Importance: Medicinal value of willow bark, salicylic acid. Populus trees often grown for wood pulp products. Willow trees have been used to make basketry.
World-wide willows of the genus Salix, are also called "sallows" and "osiers". Species of willows are found mostly in riparian and other moist areas in cold and temperate regions of the Northern Hemisphere. Some shrub species with narrow leaves are called osiers and the broader-leaf more traditional plants are referred to as sallow. Sallow is from the Old English sealth, which is related to the Latin word salix, willow.
High elevation willows, in particular those from arctic and alpine regions are low-growing or even creeping shrubs. A great example is the Arctic Willow, Salix arctica found in Central Yukon, Canada located directly to the north of British Columbia. It thrives in Arctic and Tundra conditions. This species is low growing or trailing with thick branches and typically is about 6 inches (15 cm) tall (some species up to 20 inches (50 cm). Low-growing and creeping species are not at all uncommon from very high elevations as protection from heavy winds and freezing temperatures.
The genera Salix and Populus have a great many species of butterflies, moths and their caterpillars associated with their pollen and nectar. An extensive list exists. To learn more about butterflies and moths utilizing species from the Salicaceae family, and to learn what insect species are attracted to the Salicaceae family go to BOMNA, Butterflies and Moths of North America.