sandbar willow (Salix interior)
Salix exigua Nutt. ssp. interior (Rowlee) Cronquist
Salix exigua Nutt. var. exterior (Fernald) C.F. Reed
Salix exigua Nutt. var. pedicellata (Andersson) Cronquist
Salix exigua Nutt. var. sericans (Nees) Dorn
Salix fluviatilis Nutt. var. sericans (Nees) B. Boivin
Salix interior Rowlee var. exterior Fernald
Salix interior Rowlee var. pedicellata (Andersson) C.R. Ball
Salix interior Rowlee var. wheeleri Rowlee
Salix longifolia Muhl., non Lam.
Salix longifolia Muhl. var. interior (Rowlee) M.E. Jones
Salix longifolia Muhl. var. pedicellata Andersson
Salix longifolia Muhl. var. sericans Nees
Salix longifolia Muhl. var. wheeleri (Rowlee) C.K. Schneid.
Salix rubra Richardson, non Huds.
Salix wheeleri (Rowlee) Rydb.
CONFIRMATION STATUS: Confirmed.
TAXONOMY: The currently accepted scientific name for sandbar willow
is Salix interior Rowlee. While willows are often difficult to identify, the
sandbar willow can be readily recognized by its long slender leaves with
widely spaced teeth. Other similar willows have teeth that are more dense-
ly spaced along the margins of their leaves, or their leaves lack distinct
teeth altogether. Sometimes the sandbar willow is referred to as Salix
NATIVE STATUS: Native, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS: This native peren-
nial shrub has two growth forms: a small tree up to 20' tall with a trunk
up to 6" across, or a thicket of little-branched woody stems up to 6' tall.
An older tree develops gray flaking bark on its trunk, while the trunk bark
of younger trees is gray and more smooth. Woody branches and slender
stems are variably colored, but often gray or yellowish-brown and smooth.
The alternate leaves are up to 5" long and 1/3" (1 cm.) across; they are
linear in shape and remotely denticulate along their margins (small distinct
teeth that are widely spaced). Mature leaves are usually hairless; their
upper surfaces are medium green, while their lower surfaces are pale
green. At the base of each leaf, there is a short petiole that is hairless and
light green. Sandbar Willow is dioecious: male florets and female florets
are produced on separate plants in the form of catkins. Whether male or
female, a catkin consists of a raceme of florets that are arranged in a spiral-
ing pseudo-whorl. Male catkins are ¾–2" long and narrowly cylindrical in
shape; they are erect, ascending, or lean sideways. Each male floret consists
of a pair of stamens and a single oblong-oval bract that is deciduous; there
are neither petals nor sepals. The lower half of the filaments of the stamens
are densely covered with short silky hairs; the anthers of the stamens are
bright yellow. The bract is yellow and covered with short silky hairs.
Female catkins are 1½–3" long and narrowly cylindrical; they are mostly
green while immature, later becoming light brown. Each female floret con-
sist of an ovoid-conic ovary about 5-9 mm. in length and a single oval-
oblong bract that is deciduous. Both the ovary and bract are sparsely
short-pubescent to hairless. At the apex of each ovary, there is a pair of
tiny stigmas. Each fertile ovary develops into a seed capsule that splits
open into 2 parts to release numerous seeds that are minute and hairy.
These seeds are distributed by the wind. The root system is branching and
woody, often forming underground runners that develop into vegetative
offshoots. Colonies of plants are often formed from these vegetative
REGENERATION PROCESS: Sandbar willow propogates itself by
reseeding and by vegetative reproduction. Willow seeds have a short
period of viability; they must be scattered across moist ground within a
week after the seed capsules split open. A new willow shrub can be cul-
tivated by breaking off a stem and sticking it into moist ground; new
leaves will develop at the top while new roots develop below the ground
surface. This willow can spread aggressively from vegetative offshoots.
SITE CHARACTERISTICS: The preference is full or partial sun and
consistently moist to wet conditions. Different kinds of soil are tolerated,
including those that are sandy, gravelly, silty, or loamy. Standing water is
tolerated if it is temporary.
SUCCESSIONAL STATUS: There is insufficient documentation concern-
ing successional status. Its preference for full to partial sun and moist condi-
tions makes it successful in early to mid-successional stages, particularly
along rivers, lakes, and other permanent to semi-permanent situations.
SEASONAL DEVELOPMENT: The catkins usually develop at about the
same time as the leaves from mid- to late spring. However, some shrubs
bloom later during the summer.
GENERAL DISTRIBUTION: Sandbar willow has an unusual distribu-
tion. It is generally absent from the southeast, southwest, and far western
Pacific parts of the United States, but does occur in the Mississippi Valley
as far south as Louisiana and Mississippi. It is found in the Ohio Valley and
across the upper Great Plains, the mid-Atlantic states, and into New Eng-
land. It is found in all Canadian provinces except the Atlantic maritime
provinces and the far northern provinces and territories.
SKY MEADOWS DISTRIBUTION:
Shrub specimens can be found on trails marked in red.
Appalachian Trail/Old Trail
South Ridge/North Ridge
Rolling Meadows/ Lost Mountain
HABITAT TYPES AND PLANT COMMUNITIES: Habitats include
shrub swamps, borders of ponds and slow-moving rivers, gravel bars and
sandbars, lake shore beaches, marshes, damp swales in prairies, and
ditches. This weedy willow often appears in wet areas with a history of
disturbance; it can reduce soil erosion.
IMPORTANCE AND USES: The flowers are pollinated primarily by bees
and flies, including Cuckoo bees (Nomada spp.), Halictid bees, Andrenid
bees, Syrphid flies, dance flies (Empis spp., Rhamphomyia spp.), thick-
headed flies, Tachinid flies, and flesh flies. These insects seek nectar from
the flowers, although some Halictid and Andrenid bees also collect pollen.
The following oligolectic Andrenid bees are floral visitors of sandbar willow:
Andrena andrenoides, Andrena erythrogaster, Andrena illinoiensis,
Andrena mariae, and Andrena salictaria. A large number of insects feed
on the leaves and other parts of willows. Such insect feeders include the
butterfly caterpillars of Nymphalis antiopa (mourning cloak), Nymphalis
vau-album j-album (Compton tortoiseshell), Limenitis arthemis arthemis
(white admiral), Limenitis arthemis astyanax (red-spotted purple),
Satyrium acadicum (Acadian hairstreak), and Satyrium liparops strigo-
sum (striped hairstreak); also the skipper caterpillars of Erynnis icelus
(dreamy duskywing). The caterpillars of several dozen, if not hundreds,
of moth species feed on willows. Other insect feeders include numerous leaf
and flea beetles, plant bugs, aphids (Cavariella aegopodii, Chaitophorus
viminalis), leafhoppers (Idiocerus spp., Davisonia spp.), long-horned
beetles (Oberea spp., Saperda spp.), sawfly larvae (Nematus ventralis,
Trichiosoma viminalis), and thrips (Heterothrips salicis, Mycterothrips
betulae, Pseudothrips inequalis). Many of these insect feeders are an impor-
tant food source of insectivorous birds. Some birds feed on the buds or cat-
kins of willows; these include the mallard, northern pintail, ruffed grouse,
and white-crowned sparrow. Fallen willow leaves are eaten by the wood
turtle (Clemmys insculpta) and snapping turtle (Chelydra serpentina),
while the seed capsules are sometimes eaten by the fox squirrel, gray
squirrel, and red squirrel. Willow branches are a favorite food source of
beavers; they also use the branches in the construction of their lodges and
dams. White-tailed deer and elk also browse on the leaves and twigs. In
general, the value of willows to wildlife is high.
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