WSU Extension

Hortsense

Weeds : Poison ivy and Poison oak : Toxicodendron spp. (Rhus spp.)
(revision date: 4/7/2021)

Family: Anacardiaceae
Cycle: Perennial
Plant Type: Broadleaf

Use Integrated Pest Management (IPM) for successful weed management.

Biology
Western poison ivy (Toxicodendron rydbergii) is a woody shrub or occasionally a climbing woody vine that may reach 3 to 9 feet. Pacific poison oak (T. diversilobum) is a woody vine reaching several yards in length, or occasionally a shrub to 6 feet. Leaves of both consist of three leaflets on a long petiole. The two side leaflets have short stalks, the center leaflet has a longer stalk. While poison ivy leaflets are sharply pointed at the tips, poison oak leaflets have wavy or lobed margins with rounded tips and lateral leaflets may lack stalks. Young leaves are shiny red, while older leaves are glossy green. Leaf undersides are lighter green with a coat of velvety hairs. The foliage is strikingly colored in the fall. Flowers occur in clusters on slender stems in the axils of the alternate leaves. The greenish-white blossoms are about 1/4 inch across. The ridged, berrylike fruits are greenish and resemble tiny pumpkins when immature. At maturity, they are cream-colored to whitish, reaching about 1/4 inch across. Plants reproduce by seeds and creeping root systems. SPECIAL INFORMATION: An irritant oil is present in all parts of the plant, including the roots. The oil is also present in dried plant tissues. Contact may result in a severe skin rash. Wash with COLD water and soap after contact. Smoke from burning plants may also carry the oil. Avoid contact or inhalation of smoke.
Habitat
Poison ivy and poison oak are commonly found in moist places, and along roadsides, railroads, and fencerows. While poison oak is more common west of the Cascades, poison ivy is found mostly east of the Cascades.

Management Options

Non-Chemical Management
None recommended
Select non-chemical management options as your first choice!

Chemical Management

Apply according to label instructions when plants are actively growing. Use glyphosate products for spot treatments only! NOTE: Some ingredients listed here are only available in combination. Read the label carefully on combination products to make sure the product is suitable for your specific situation.

Landscape areas
  • glyphosate
  • products containing triclopyr
Turf areas
  • triclopyr
Bare ground areas
  • glyphosate
  • triclopyr
Images
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Caption: Poison ivy leaves
Photo by: J.A. Kropf
Caption: Poison ivy
Photo by: J.A. Kropf