Ontario Weeds: Poison sumac

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Name
  2. Other Names
  3. Family
  4. General Description
  5. Stems and Roots
  6. Leaves
  7. Flowers and Fruit
  8. Habitat
  9. Similar Species
  10. Caution
  11. Related Links

Name: Poison sumac, Rhus vernix L.

Other Names: sumac à vernis, Poison elder, Poison dogwood, bois chandelle

Family: Cashew Family (Anacardiaceae)

General Description: Coarse shrub or small tree 1.5-7m (5-23ft) high, often branched at the base, with brown to gray smoothish bark;

Photos and Pictures

Poison sumac.

Poison sumac. End portion fo a twig with 2 compound leaves and 2 clusters of small white berries.
Poison sumac.
End portion fo a twig with 2 compound
leaves and 2 clusters of small white berries.

Stems & Roots: Branches hairless, very slightly roughened with tiny, wart-like surface glands, and bearing prominent leaf scars.

Leaves: Leaves alternate on the branches, but each leaf pinnately compound with 3 to 6 pairs of leaflets that are nearly opposite each other, plus 1 terminal leaflet; each leaflet 4-10cm (1½-4in.) long and ½ to 2/3 as wide, somewhat rounded at the base and pointed (acuminate) at the tip, dark green above and lighter green below; margins of leaflets are usually smooth but occasionally may be wavy, irregularly lobed or coarsely toothed; the whole compound leaf (7-13 leaflets plus their central stalk) falling from the branch in autumn.

Flowers & Fruit: Flowers dull white, produced in 4-20cm (1½-8in.) long, spreading or pendulous panicle-like clusters that arise from leaf axils; berries whitish or drab, 4-5mm (1/6-1/5in.) long. Flowers in July.

Habitat: Poison sumac is found in southern Ontario in wet woods and edges of swamps and lakes.

Similar Species: Poison sumac is distinguished by its appearance as a coarse shrub or small tree, its alternately arranged, pinnately compound leaves with 7-13 usually smooth-margined leaflets and its clusters of white flowers followed by whitish berries. Prickly-ash and the true Ash trees, Fraxinus spp., [frêne] also have pinnately compound leaves with smooth margins on their leaflets, but Prickly-ash has pairs of large prickles along its branches and smaller ones at the bases of some of the leaflets, and the true Ash trees have their compound leaves in opposite pairs along the branches. Staghorn sumac, Rhus typhina L., [RHUTY, sumac vinaigrier, sumac amarante, vinaigrier], a very common shrub with velvety-hairy branches (hence its common name), sharply and coarsely toothed leaflets in pinnately compound leaves that turn vivid red in fall, and cone-shaped clusters of red fruits is not poisonous.

Caution: The entire plant is as poisonous to most people as is Poison-ivy. Because both the foliage in summer and the bare twigs in winter can cause severe dermatitis, take special care to avoid these parts touching hands or face when in damp woods.

Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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