This multi-branched shrub is 2-6' tall. Branchlet bark is brown,
reddish brown, or pale yellow, relatively smooth, and glabrous. Young
shoots are light green and short-pubescent. Alternate leaves occur
along the smaller branchlets and shoots. Individual leaves are 1½-4"
long and ¼-¾" across; they are oblong-elliptic or oblong-oblanceolate
in shape with margins that are smooth, slightly undulate, or slightly
crenate-dentate with remote teeth. Often, the leaf margins
are revolute (rolled under). Leaf bases
while their tips are relatively short and blunt. The upper sides of
mature leaves are medium green and glabrous, while their lower sides
are pale green to white, mostly glabrous, and glaucous. Sometimes fine
hairs occur along the lower side of the central veins. Immature leaves
are pale yellowish green or reddish green and they are usually more
hairy than mature leaves. The petioles are light green, pale yellow, or
nearly white; they are either glabrous or short-pubescent. Sometimes
lanceolate stipules occur in pairs at the bases of petioles. These
stipules are about 3-8 mm. long and deciduous.
Prairie Willow is
dioecious, producing either all male (staminate) or all female
(pistillate) catkins on separate shrubs. Male catkins are ¼-¾" long,
consisting of numerous male florets. Initially, male catkins are fuzzy
and gray, but they later become more red or yellow from the anthers of
their stamens. Each male floret consists of 2 stamens and a silky-hairy
bract about 1.5-2.0 mm. in length. The female catkins are ½-2" long,
consisting of numerous female florets. Initially, female catkins are
somewhat fuzzy and gray, but they later become green, and finally light
brown. Each female floret consists of a lanceoloid pistil about 4-8 mm.
in length and a silky-hairy bract about 1.5-2.0 mm. in length. There
are short pedicels underneath the female florets. The blooming period
occurs from early to mid-spring for about 1 week. Afterwards, during
late spring or early summer, fertile female florets are transformed
into seed capsules that split open at maturity to release their seeds.
The tiny seeds are embedded in cottony hairs; they are distributed by
the wind. The woody root system is shallow and branching. This shrub
reproduces by reseeding itself.
The preference is full or partial sun, moist to dry-mesic conditions,
and soil that is loamy or sandy. Most growth and develop occurs from
spring to mid-summer. The tiny seeds remain viable for about 1-2 weeks.
new clonal shrub can be created by cutting a branchlet from an older
shrub during the early spring and sticking the cut-end of this
branchlet into moist ground.
The native Smooth
Prairie Willow is relatively uncommon in Illinois, where it is found in
widely scattered counties (see Distribution
). Habitats include
moist to mesic prairies, moist to mesic sand prairies, willow thickets,
sandy and non-sandy savannas, bases of sandstone bluffs, and sedge
meadows. This shrub adapts to both well-drained upland areas and poorly
drained bottomland areas.
The florets of the catkins are
insects. These floral visitors include Cuckoo bees (Nomada spp.
Andrenid bees (Andrena
), Halictid bees (Halictus
sawflies (Dolerus spp.
miscellaneous beetles, and other insects. Andrenid bees that
specialist pollinators (oligoleges) of willows (Salix spp.
, and Andrena
. Smooth Prairie
Willow and other willows are host plants to a variety of insects that
feed on their leaves, bore through their branchlets, or suck plant
juices. These species include the leafhoppers Empoasca andresia
and Erythroneura rosa
(Carrot-Willow Aphid), Chaitophorus
(Small Black & Green Willow Aphid), and Tuberolachnus
(Giant Willow Aphid); Lopidea salicis
(Willow Plant Bug) and
other plant bugs; the leaf beetles
(Willow Flea Weevil); the
wood-boring larvae of Agrilus
(Common Willow Agrilus); larvae
of the gall flies Dasineura
larvae of Nematus
(Willow Sawfly), Pontania proxima
Redgall Sawfly), and Pontania
(Willow Gall Sawfly); and
(Prairie Walkingstick). Some vertebrate animals use
willows as a source of food and protective cover. The buds are eaten by
the Ruffed Grouse, while the catkins are eaten by the White-Crowned
Sparrow. Such birds as the Yellow Warbler, Warbling Vireo, and
Yellow-Breasted Chat use these shrubs for protective cover and nesting
habitat. The twigs and foliage are browsed occasionally by the
White-Tailed Deer and Cottontail Rabbit.
A wildflower garden in Urbana,
Some authorities don't recognize Smooth Prairie Willow as a
distinct variety of Prairie Willow, although Mohlenbrock (2002) does.
Smooth Prairie Willow is very similar to the typical variety of Prairie
Willow, except that its leaves are hairless, or nearly
Prairie Willow resembles the native Salix discolor
except that its leaves and stipules are more narrow than those of the
latter. Another variety of Prairie Willow, Salix humilis microphylla
(Sage Willow), is a shrub about 1-3' tall that
leaves and smaller catkins. This latter variety prefers dry open
areas; it is relatively uncommon in Illinois.