poison sumac

LC - Least Concern

N5 - Secure

SNR - Unranked

not listed

OBL - Obligate wetland

OBL - Obligate wetland

Poison sumac is a fast-growing, short-lived, deciduous, tall shrub or very small tree. It can be 10′ to 25′ tall and up to 6″ in diameter at breast height, though in Minnesota it is usually no more than 15′ in height and 2 ″ in diameter.

The trunk is slender and is often branched near the base, and there are often vegetative sprouts at the base. The crown is small and rounded, with just a few wide-spreading branches.

The bark is thin, light gray, and smooth or shallowly fissured.

The twigs are moderately stout and orangish-brown or yellowish-brown. They are covered with conspicuous dark dots and splotches, and have numerous prominent, horizontal pores (lenticels). The leaf scars are large and shield-shaped, and has a number of scattered bundle scars. The terminal buds are broadly cone-shaped, ⅜″ to ¾″ long, and are covered with downy scales. When broken or cut, the twigs exude a dark sap.

The leaves are deciduous, alternate, 6″ to 12″ long, and pinnately divided into 7 to 13 leaflets. They are on ¾″ to 3½″ long leaf stalks (petioles). The petiole and the central axis of the leaf (rachis) are red or yellowish-red. The rachis is hairless. The lateral leaflets are stalkless of on very short stalks. The terminal leaflet is on a ⅜″ to 1¼″ long stalk (petiolule).

The leaflets are oblong to inversely egg-shaped or elliptic, 2″ to 4″ long, and 1″ to 1¾″ wide. They are wedge shaped at the base at an angle less than 90° and taper abruptly to a long point at the tip with concave sides along the tip. The upper surface is dark green, shiny, and hairless. The lower surface is pale green and hairless. The margins are untoothed. In autumn the leaves turn orange or red.

Male and female flowers are usually borne on separate plants. They appear in early to late June after the leaves have developed. The inflorescence is a loose, branched cluster (panicle), up to 8″ long and 4″ wide, rising from the leaf axils of first-year twigs. The flower stalks may be hairless or covered with short hairs. The panicle is more or less erect in flower, conspicuously drooping in fruit.

Individual flowers are about ⅛″ long. There are 5 sepals, 5 petals, 5 stamens on the male flower, and 1 style on the female flower. The sepals are green to cream-colored, united at the base, and divided into 5 teeth at the tip. The petals are greenish-yellow and 1 ⁄16″ to ⅛″ long. The stamens have white stems (filaments) and yellow anthers and protrude beyond the petals. The style has 3 lobes.

The fruit is an almost spherical, ⅛″ to 3 ⁄16″ in diameter, fleshy, berry-like drupe. It is green and shiny at first, turning white or ivory-colored when ripe. It matures in late August to late September and persists on the plant throughout the winter.

10″ to 15″

Greenish-yellow

Wet. Mostly swamps but also marshes and wet meadows. Shade. Saturated, sandy or peaty soils.

Early to late June

The sap of poison sumac contains the allergenic urushiol. Urushiol is not a single chemical but a complex of five chemicals called alkylcatechols.

Several exposures to the substance may be necessary to impart sensitivity. Research has shown that 85% of all people will develop contact dermatitis after adequate exposure. It usually takes 12 to 48 hours for a rash to develop on a previously sensitized person. In some individuals, a single exposure will cause a reaction. In these individuals, the rash will develop in seven to ten days.

The lesions last 14 to 20 days. Rashes do not spread and are not contagious. Treatment can dry the blisters, reduce swelling, and relieve itching, but will not speed healing.

Contact with the outer surface on an undamaged plant should not cause an allergic reaction unless there is residual urushiol present from a previous injury to the plant or a nearby plant. Contact with a torn leaf, broken or damaged stem or rhizome, or black spot will cause a reaction in those sensitized to urushiol.

Sources

2, 3, 4, 5, 8, 24, 28, 29, 30.

Native

Uncommon in Minnesota

Location: Boot Lake SNA

Location: Willmar, MN

Location: Tamarack Nature Center