No. 024 · plant · Risk: Moderate
Pacific Poison Oak
Toxicodendron diversilobum
In season · SeptemberPacific West
- Field tell
- Oak-like lobed leaflets in threes; glossy green in summer, brilliant red in fall.
- Why it matters
- Same urushiol oil as poison ivy; the most common plant rash on West Coast trails.
- Season
- Leaves spring–fall; bare stems remain allergenic in winter.
PLANT RASH
If you touch poison ivy, oak, or sumac
- Rinse skin with cool running water and soap as soon as you can — within minutes if possible.
- Wash clothes, tools, and pet fur that may have oil on them; urushiol stays active.
- Do not burn the plants; the smoke can carry oil into lungs and eyes.
- Use calamine, hydrocortisone, or an oral antihistamine for itching. See a clinician for rash on the face, genitals, or over a large area, or if you have trouble breathing.
Not medical advice. Call 911 or Poison Control 1-800-222-1222.
Related plants
- Poison Ivy — Three almond-shaped leaflets; 'leaves of three, let it be.' Can vine up trees or grow as a shrub.
- Poison Sumac — 7–13 smooth-edged leaflets on a red stem; grows as a shrub or small tree in wet ground — not the fuzzy roadside sumac.