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Wisconsin Plant of the Week

Toxicodendron vernix (L.) Kuntze

Anacardiaceae (Cashew Family)

Common Name:

poison sumac

06/07/1999

Poison sumac is a native shrub found in tamarack swamps, on floating mats of bogs and in shady borders of marshes, to 5 m tall.  Bruising any part of the plant breaks resin canals to release an oil, as in poison ivy, that causes contact dermatitis for many. The oil can be carried on clothes, in droplets of smoke or on the surface of water.

In June small white-yellow flowers bloom in clusters in the axils of leaves.  By late summer white berries hang in long loose clusters.

Leaves are alternate and pinnately compound. The leaflets are shiny, 4-5 cm long, with a smooth edge (entire) and a pointed tip (acuminate). Each leaflet is slightly folded upward along its long axis, and the leaflets are arranged on the rachis to form a shallow "V". This helps to recognize the plant from a distance. Where the plant gets more sun, the rachis is more red. Like the uplands sumacs, the leaflets turn bright red in the fall.

Poison sumac is easily distinguished from the non-poisonous upland sumacs by habitat.  The upland sumacs also have a terminal inflorescence, fruit that's red and pubescent in erect clusters, and dull green toothed leaflets.

  • Origin of the name: Toxicodendron: toxicum, L., poison; dendron, Gr., a tree; vernix, L., varnish, the sap of a similar Asian species is a principle source of lacquer.
  • Range:  an eastern coastal plain species, from s. ME to MN, MD to FL and TX
  • WI Range: Southern WI, north to Wood and Waupaca Co.
  • Common associates:  Tamarack, bog birch, pitcher plant, skunk cabbage
  • Wetland Indicator Status: OBL
  • Coefficient of Conservatism: C = 10 (S&W), C = 6 (MI)
     
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