SALIX (THE WILLOWS)
B. Michelle Smith, Ecology 350
Description: Common characteristics of the willows include: lateral twigs from younger trees tend to snap off easily, soft, lightweight wood, bitter bark, sizes ranging from shrub to tree, alternate leaves, male and female on separate plants, fruit contains seeds with cottony hairs, narrow leaves (Knopf, 1980. )
Species in the genus Salix
Note: This list is considered complete by Christopher Newsholme (see references). Different sources listed different numbers of species, ranging from 350 up to 500. Where possible, the common name in included along with the Latin name.
Identification Guide: Willows are often considered very difficult to distinguish from each other. Because they often hybridize, the problem is compounded (Duncan & Duncan, 1988). Listed in the following identification guide are the willows of the southeastern United States with descriptions quoted from The National Audobon Society Fieldguide to North American Trees and Salix in the Southeast. For further identification, see these sources. The seeds are kept in catkins, which are basically long, scaly cones. The reason they are called catkins is because the seeds that they contain have tufts of hair which appear fuzzy (also hence the name pussywillow).
This identification key includes direct quotes on identification from the previous listed sources plus simple characteristics that may help someone without a field guide identify some of the better known species. (from Gray's Manual of Botany 1950).
- S. alba (White willow) "Naturalized tree with 1-4 trunks and open crown of spreading branches. Height 50-80’. Leaves 2-41/2" long, 3/8-11/4" wide, lance-shaped to elliptical, finely saw-toothed, shiny dark green above, whitish and silky beneath. B ark gray, rough furrowed into narrow ridges. Twigs yellow to brown, flexible and often drooping. Flowers catkins 11/4"-21/4" long with yellow, hairy scales. Fruit 3/16" long, hairless capsules, light brown. Habitat wet soils of stream banks and valleys near cities."(Knopf, 1980). Branchlets flexible & silky, leaves silky-white, leaves finely serrate.
- S. amygdaloides (Peach Willow, Almond willow) "Tree with 1 or sometimes several straight trunks, upright branches and spreading crown, Height 60’. Leaves 2-41/2" long, 1/2-11/4" wide, lance-shaped, often slightly curved to one side, tapering to long, narrow point, finely saw-toothed, shiny green above, whitish beneath. Bark dark brown, rough, forrowed into flat scaly ridges. Twigs shiny orange or brown. Flowers catkins 11/4"-3" long, with yellow hairy scales. Habitat wet soil of valleys, often bordering stream banks" (Knopf, 1980). Drooping yellowish brachlets which are flexible. Pale green above, white below.
- S. babylonia (Weeping willow) "A handsome, naturalized tree with short trunk and broad, open, irregular crown of drooping branches. Height 30-40". Leaves 21/2-5" long, 1/4-1/2" wide, narrowly lance-shaped with long pointed tips, finely saw-toot hed, dark green above, whitish or gray beneath. Bark gray, rough, thick, deeply furrowed in long, branching ridges. Flowers catkins 3/8-1" long, greenish. Fruit 1/16" long, light brown capsules. Habitat parks, gardens and cemeteries especially near water" (Knopf, 1980). Large tree, drooping branches, leaves whitish underneath, finely serrate.
- S. bebbiana (Beak willow, Diamond willow) "Much branched shrub or small tree with broad, rounded crown. Height 10-25’. Leaves 1-31/2" long, 3/8-1" wide. Elliptical, sharp-pointed at ends, slightly saw-toothed or wavy, dark green above and gray or whitish beneath and net-veined beneath. Bark gray, smooth becoming rough or furrowed. Twigs reddish-purple, slender, widely forking. Flowers catkins 3/4-11/2" long with yellow or brown scales. Fruit 3/8" long very slender capsules, hairy, light brown, ending in long point. Habitat moist open wetlands and borders of streams, lakes, and swamps" (Knopf, 1980). Leaves are gray or opaque above.
- S. caroliniana (Carolina willow, coastal plain willow) "shrub or small tree with spreading or slightly drooping branches. Leaves 2-4" long, 1/2-1/4" wide, lance-shaped, finely saw-toothed, green above, whitish below. Leafstalks hairy. Bark gray to blackish, fairly smooth, furrowed into broad scaly ridges. Twigs brown, slender. Flowers catkins 3-4" long, greenish or yellowish. Fruit 1/4" long, light-reddish brown, habitat wet soils of stream banks and swamps, range S. Pennsylvania south to S. Florida, werst to central Texas and north to SE Nebraska" (Knopf, 1980). Very similar to S. nigra. Brachlets are brittle, sometimes yellowish-purplish. Leaves white beneath.
- S. eriocephala "shrub .2-6 m tall. Branches reddish brown, buds yellowish brown, leaf blades commonly narrowly oblong. Occurs on gravelly or rocky river and stream banks, in marshy fields, and in mixed mesophytic woods on alluvium" (Argus, 1986 ). Shrub with black bark. Leaves dull green above.
- S. floridana (Florida willow) " shrub or small tree with large broad leaves. Height 7-15’. Leaves 2-5" long, 3/4-11/2" wide, larger on young twigs. Elliptical or ovate, very short, scattered, gland-teeth, dark green and hairy only on yellowish mid-vein above, whitish with soft hairs below. Bark gray-brown, smooth, becoming rough at base. Twigs brown or purplish. Flowers catkins 11/2-21/4" long with yellowish hairy scales. Fruit about 1/4" long, long pointed capsules, light brown. Habitat wet soils along small streams and in wet limestone areas" (Knopf, 1980).
- S. fragilis (Crack willow, snap willow) "Large, naturalized tree with widely forking branches and very brittle twigs. Height 80’. Leaves 4-6" long, 1-11/2" wide. Lance-shaped, ending in long point turned to one side, coarsely saw-toothed. Shiny green above, whitish beneath. Bark gray, rough, thick. Twigs shiny brownish. Flowers catkins 1-21/4" long with yellow or greenish hairy scales. Fruit 3/16" long light brown capsules. Habitat escaping in moist soil along roadsides and streams and in clear ings" (Knopf, 1980). Branches are divergent, brittle at base. Leaves are coarsly serrate & shiny green above.
- S. humilis "Branches reddish brown, tomentose with gray, white, or brownish hairs. Buds reddish brown, oblong, flat-beaked. Leaf blade acute to obtuse. Occurs in dry, open oak-pine woods, prairies, grassy and rocky heath balds, limestone and serpentine barrens, wet flatwoods and meadows" Argus, 1986). Branches appear wandlike. Leaves gray-green above.
- S. lucida "Shrubs or trees up to 6m tall. Branches reddish brown or yellowish, buds yellowish brown. Shiny leaves green on both sides. Rare in southeastern US" (Argus, 1986). Similar to S. pentandria--leaves may be paler underneath. Leaves come to a sharp, narrow point.
- S. nigra (Black willow, swamp willow) "Large tree with 1 or more straight trunks and usually leaning trunks, upright branches, and narrow or irregular crown. Height 60’100’. Leaves 3-5" long, 3/8-3/4" wide. Narrowly lance-shaped, often slightly curved to one side, long pointed, finely saw toothed, shiny green above, paler below. Bark dark brown or blackish . Twigs brownish, very slender. Flowers catkins 1-3" long, with yellow hairy scales. Fruit 3/16" long, reddish brown capsules, hairless. Hab itat wet soils of banks and lakes" (Knopf, 1980). Leaves green both sides, branchlets tend to snap off easily, slanting multiple trunks,
- S. pentandra (Bay leaved willow) "Shrubs or trees up to 7m tall. Branches dark reddish brown. Buds yellowish brown. Immature leaf blades reddish. Similar to S. Lucida" (Argus, 1986). Shrub with leaves that are green on both sides. Leaves are often sticky.
General Information: All member of the genus Salix are dioecious , male and female are on separate trees (Massey, 1944). They occur on all continents except Australia, and are most common in the Northern Hemisphere (Everett, 1983). The bark is soft and lightweight and is often used in making plywood, veneer and matchsticks (Duncan & Duncan, 1988). Other uses have included making aspirin, (hence salic acid) and Eskimo kayaks (Everett, 1983). They are commonly eaten by mammals, including deer and rodents (Massey, 1944) and produce a favorite pollen of bees (Duncan & Duncan, 1988).
Sizes of the members of the genus range from small shrubs and bushes to large trees. The largest native tree of the United States is S. nigra. Most tree-sized species (other than S. babylonia) are not used in cultivation because their long, thick roots tend to spread out and interfere with walkways, streets, and irrigation or sewer systems (Newsholme, 1992).
S. babylonia - Weeping willow
S. nigra - Black willow