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Salicaceae

Salicaceae A family of dicotyledonous (see DICOTYLEDON) trees and shrubs that have alternate, deciduous, simple leaves with stipules and tiny flowers, in unisexual catkins which are borne on separate male and female plants. The flowers have no perianth, merely a basal bract, and have either 2 to many stamens, or a 1-celled, bicarpellary ovary with 2 stigmas. The trees are mainly wind-pollinated. The fruits are capsules, and the seeds bear long, silky hairs, which help in wind dispersal. Some are important timber trees. There are two genera (Salix and Populus), comprising 330–50 species, most occurring in the northern temperate zone.

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"Salicaceae." A Dictionary of Plant Sciences. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"Salicaceae." A Dictionary of Plant Sciences. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/salicaceae

"Salicaceae." A Dictionary of Plant Sciences. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/salicaceae

Willow Family (Salicaceae)

Willow Family (Salicaceae)

Biology of willows

Species of willows

Economic and ecological importance of willows

Resources

Willows are a diverse group of about 300 species of woody angiosperm plants in the genus Salix, family Salicaceae. Willows are widely dispersed and occur on all continents except Antarctica, but they are most diverse in cooler regions of the Northern Hemisphere.

All willows are woody plants, but the species vary greatly in size. Some species of willows are trees that can grow taller than 49 ft (15 m), while others are dwarf shrubs of the tundra that never get any taller than a few centimeters.

Biology of willows

Willows have simple, slender leaves, alternately arranged on the twigs, and with toothed or entire margins. The foliage of willows is seasonally deciduous, being shed in the autumn. Willow plants are dioecious, meaning that particular individuals bear either male or female flowers but not both. Both types of flowers usually produce nectar so that pollination is by insects. The flowers of willows are arranged in elongate inflorescences, known as catkins. The fruits are a capsule, containing tiny seeds with tufted hairs that make them aerodynamically buoyant so that they can be dispersed widely by the wind.

Willows are rather fast growing woody plants, but they are relatively short lived. Some species of willows sprout prolifically, and they may form dense thickets in moist, recently disturbed habitats. Most willows are relatively easy to cultivate from stem cuttings.

The usual habitat of willows is moist places, often beside streams, rivers, lakes, and other surface waters.

Species of willows

More than 100 species of willows are native to North America. Most of these are shrubs or dwarf shrubs, but about forty species reach tree size. Willow species commonly hybridize with each other and this, along with their relatively great richness of species, can make some of the willows difficult to identify.

Some of the more common species of willow that can attain the size of trees include the following: the black willow (Salix nigra ) is a widespread tree in low-lying and riparian habitats in the eastern United States and southern Ontario; the peachleaf willow (S. amygdaloides ) is also widespread in central North America; the Pacific willow (S. lasiandra ) is another tree-sized species, occurring widely from southern California to central Alaska.

Shrub-sized species of willows are richer in species and include the following: The sandbar willow (S. interior ) occurs widely in eastern and central North America and through the boreal forest to central Alaska. This species often forms thickets in flat, moist, alluvial habitats. The arroyo willow (S. lasiolepis ) occurs in moist canyons and along streams in the western United States. The Mackenzie willow (S. mackenzieana ) is a northwestern species. The coastal plain willow (S. carolineana ) is widespread in the southeastern United States. The Bebb willow (S. bebbiana ) is a common shrub of boreal and cool-temperate regions. The feltleaf willow (S. alaxensis ) is widespread in the northeastern boreal forest.

Many species of willows are dwarf shrubs, occurring in alpine and arctic tundra. The stems of these tiny willows grow horizontally along the ground, and in some cases they never rise any higher than several centimeters above the ground surface. The most widespread of the dwarf willows is the arctic willow (S. arctica ). This species occurs throughout much of the tundra of North America, Greenland, and Eurasia, as far north as the limits of land. Another arctic species is the reticulated willow (S. reticulata ).

Economic and ecological importance of willows

Many species of willows are important ecologically. Willows are often species of early succession, and they are important in the early and middle stages of successional recovery after disturbance. Willows are commonly an important browse of mammals such as deer, moose, rabbits, hares, and other species, especially during the winter when herbaceous forage is not very available.

Tree-sized willows are sometimes used for lumber. The black willow is the only species used much for this purpose in North America. Because its wood is not very strong, it is generally used to manufacture boxes and similar goods.

Because willows can be so productive, there has been research into the cultivation of tree-sized willows in plantations for use as a biomass fuel. This use of willows as a source of renewable energy may prove to be important in the future. The willow biomass can be burned directly, or it can be chemically converted into more easily portable liquid fuels such as alcohol or a synthetic, petroleum-like mixture which can be manufactured under heat and pressure.

Because willows grow quickly and are so easy to propagate using stem cuttings, they are often used to vegetate stream banks to help prevent erosion and sometimes to re-vegetate other types of disturbed lands.

Willows have long had some use in folk medicine. Many cultures are known to have chewed willow twigs to relieve pain and fever. The original source from which salicylic acid was extracted was the bark of the white willow (S. alba ) of Europe. This chemical is used to manufacture acetylsalicylic acid or ASA (sometimes known as aspirin), an economically important analgesic useful for treating pain, fever, and inflammation.

KEY TERMS

Browse A food consisting of the foliage, twigs, and flowers of woody plants.

Catkin An elongate, spikelike cluster of unisexual flowers, often drooping at maturity. Catkins are the floral type of the willow family.

Dioecious Plants in which male and female flowers occur on separate plants.

Willows may be an important source of nectar for bees in the early spring, a time when few other species of insect-pollinated plants are flowering. Willow honey may be a locally significant product in some areas.

Willow twigs are rather flexible and have been used to weave baskets, for caning, and to make woven fences and other lattices.

Some species of willows have good aesthetics and are utilized in horticulture. One of the best known species for this purpose is the weeping willow (Salix babylonica ), a beautiful, pendulous tree. This species is native to northern China. However, the weeping willow was considered to be so beautiful by the famous Swedish botanist Carl von Linnaeus, who gave the species its scientific name, that he decided that it must have been present in the biblical Garden of Babylon; hence, the origin of the geographically inaccurate, scientific binomial of the weeping willow.

The weeping willow has been widely introduced to North America as an ornamental tree. Other non-native species that are commonly used in horticulture include the crack willow (S. fragilis ) of Eurasia and the white willow (S. alba ) and basket willow (S. viminalis ) of Europe. Some of these species have escaped from cultivation and have become locally invasive in natural habitats.

Wild willows also have pleasant aesthetics. Most famous in this sense are the several species known as pussy willows, especially the pussy willow (Salix discolor ). These species produce large, attractive catkins in the early springtime. In fact, stems of these species can be collected in the late winter before they have bloomed and placed in water in a vase. In a short time, the pussy-willow stems will bloom indoors to pleasantly herald the arrival of spring.

Resources

BOOKS

Judd, Walter S., Christopher Campbell, Elizabeth A. Kellogg, Michael J. Donoghue, and Peter Stevens.

Plant Systematics: A Phylogenetic Approach. 2nd ed. with CD-ROM. Suderland, MD: Sinauer, 2002.

Bill Freedman

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"Willow Family (Salicaceae)." The Gale Encyclopedia of Science. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"Willow Family (Salicaceae)." The Gale Encyclopedia of Science. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/willow-family-salicaceae-0

"Willow Family (Salicaceae)." The Gale Encyclopedia of Science. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/willow-family-salicaceae-0