Pacific poison oak (Toxicodendron diversilobum) is in the Cashew Family family (Anacardiaceae). Across the U.S., iNaturalist users have logged 1,223 research-grade flowering observations of it in our sample, peaking in April.
Nationally it blooms mainly from March to May, but timing varies a lot by state and elevation — see the table below.
When to photograph Pacific poison oak: observations by month (U.S.)
About Pacific poison oak
Toxicodendron diversilobum (syn. Rhus diversiloba), commonly named Pacific poison oak or western poison oak, is a woody vine or shrub in the Anacardiaceae (sumac) family. It is widely distributed in western North America, inhabiting conifer and mixed broadleaf forests, woodlands, grasslands, and chaparral biomes. Peak flowering occurs in May. Like other members of the Toxicodendron genus, T. diversilobum causes itching and allergic rashes in many humans after contact by touch or smoke inhalation.From Wikipedia via iNaturalist — article, CC BY-SA.
Pacific poison oak by state
| State | Observations | Peak month | Main season |
|---|---|---|---|
| California | 966 | April | Mar–May |
| Oregon | 203 | May | May–May |
| Washington | 54 | May | May–Jun |
Main season = months with at least 30% of the state's peak-month count.
Related wildflowers (Cashew Family)
Photography tips
- Photograph flowers on calm, overcast mornings to avoid wind blur and harsh shadows.
- Get low: a shallow depth of field (f/2.8–f/5.6) isolates a bloom against soft color.
- Stay on trails — trampling meadows kills plants and ruins next year's display.
- Try a kaleidoscope abstract of a single bloom with our online kaleidoscope tool.
FAQ
When is the best time to photograph Pacific poison oak?
Nationally, April has the most observations, with the main season from March to May.
Where is Pacific poison oak most often seen?
The most observations come from California, Oregon, Washington.