This shrub is 10-25' tall, consisting of a trunk up to 6" across
and a relatively open crown. Trunk bark is light gray and relatively
smooth, except for scattered lenticels that resemble small bumps.
Branch bark is also light gray and more smooth, while twigs
are orange, tan, or brown and usually glabrous (less often
pubescent); twigs have numerous small lenticels and prominent
terminal buds that are purplish red. Alternate compound leaves occur
along the twigs; these leaves are 6-14" long and odd-pinnate with 7-13
leaflets. Petioles and rachises of the compound leaves are red to
yellowish red and glabrous. Individual leaflets are 2-4" long and 1-1¾"
across; they are ovate or oblong-ovate and smooth along their margins.
The petiolules (basal stalklets) of the leaflets are up to ¼"
long and usually bright red. The upper surface of the leaf blades is
medium to dark green and glabrous, while the lower surface is pale
green and usually glabrous (less often sparsely pubescent). During the
fall, the deciduous leaflets turn orange or red.
Because Poison Sumac is usually
dioecious, the same shrub produces either all male (staminate) or all
female (pistillate) flowers. Less often, both male and female flowers
are produced on the same shrub, while other shrubs produce perfect
flowers. The flowers are produce in panicles from the axils of the
compound leaves; individual panicles are up to 8" long and 4" across.
The peduncles and petioles of these panicles are glabrous or finely
pubescent. Individual flowers are about 1/8" (3 mm.) across, consisting
short green calyx with 5 teeth and 5 green or greenish yellow petals.
Each male flower has 5 stamens, each female flower has a pistil with a
single style, while a perfect flower has both a pistil and 5 stamens.
The filaments of the stamens are white, while their anthers are yellow.
The blooming period occurs from late spring to early summer for about 2
weeks. Fertile female and perfect flowers are replaced by one-seeded
drupes during the summer. Individual drupes are about ¼" across,
globoid to ovoid in shape, and glabrous. They are initially green,
but become white or grayish white at maturity. The panicles of drupes
have a tendency to droop downward; they can persist on the shrub
through the winter. This shrub has a tendency to form vegetative
sprouts from the base.
The preference is full or
partial sun, wet to moist conditions, and mucky, peaty, or sandy soil
that contains decaying organic material. The soil pH should be more or
less acidic. This shrub can tolerate standing water for
several months each year.
Illinois, Poison Sumac is an uncommon native shrub that is found
primarily in NE Illinois (see Distribution
). Habitats include both
sandy and non-sandy marshes, sandy and non-sandy swamps, shrubby and
forested bogs, shrubby fens, and soggy thickets along rivers. In
some wetlands, Poison Sumac can become one of the dominant shrubs, but
this is highly unusual in Illinois. Generally, Poison Sumac is found in
higher quality wetlands where the native flora is still intact.
The flowers are cross-pollinated by small
bees and flies,
which seek nectar and pollen. A few insects have been observed to feed
on the leaves of Poison Sumac. These species include the caterpillars
of the moths Eutelia
(Beautiful Eutelia), Marathyssa
(Dark Marathyssa), and Paectes oculatrix
(Eyed Paectes). Both
the adults and larvae of Blepharida
(Sumac Flea Beetle) also feed
on the foliage. The whitish drupes are eaten by the Ruffed Grouse,
Ring-Necked Pheasant, Bobwhite, and undoubtedly other birds,
particularly during the winter, when other sources of food are scarce.
The Cottontail Rabbit has been observed to gnaw on the bark and twigs
of young shrubs.
Edge of a sandy marsh at Cowles Bog in northwest
Like the more common Toxicodendron
(Poison Ivy), all parts of
this shrub exude a floral oil (uroshiol) that can irritate the skin of
many individuals because its triggers an allergic reaction. While
Poison Ivy is normally a climbing woody vine with trifoliate leaves,
Poison Sumac is an erect shrub that has compound leaves with 7-13
leaflets. Poison Sumac prefers habitats that are more wet than those in
which Poison Ivy occurs, and so these two species are rarely seen
together. Poison Sumac is similar in appearance to a Sumac (Rhus sp.
but its leaflets have smooth margins rather than toothed, and its
drupes are white and glabrous rather than red and hairy. Poison Sumac
also superficially resembles a young Ash tree (Fraxinus sp.
latter has opposite compound leaves and its fruit is a winged samara,
rather than a drupe. An older scientific name of Poison Sumac is Rhus