Western poison oak

About

A native West Coast shrub or climbing vine that carries the same rash-causing oil as poison ivy. It is common in California and western Oregon and Washington, including yards and parks next to wild land.

Also called Pacific poison oak, poison oak, Pacific poison-oak

How to identify it

Look for

Leaves usually have three leaflets with toothed or slightly lobed edges, and the middle leaflet has the longest stalk. In sun it forms a dense shrub about 1 to 6 feet tall; in shade it climbs trees with aerial roots. It has no thorns, bears small white-green flowers and whitish berries, and its leaves often turn red or orange by summer's end.

Look-alikes

Skunkbush sumac also has three leaflets, but its berries are red and hairy and its middle leaflet has no stalk. Blackberries have thorns; poison oak never does.

Where it grows

Oak woodlands, brushy hillsides, stream sides, forest edges, parks and gardens next to wild areas.

When

Flowers from March to June; whitish berries form in late summer and fall, and leaves often color red or orange by late summer.

How it spreads

Suckers from underground stems, roots where vines touch the soil, and spreads by bird-carried seeds that can wait in the soil for years.

Most common in

What to do, gentlest first

Protect yourself first. Weed killers are a last step; always read and follow the label.

1. Gear up and keep it out of play areas Prevent

   Wear washable cotton gloves over plastic gloves, long sleeves, long pants and eye protection. Afterward, wash tools, shoes and all clothing.

   Don't mow it: mowing throws oil into the air, much like burning.

2. Dig out plants, roots and all By hand

   Pull or grub out plants with a shovel in early spring or late fall, when moist soil lets the roots come out. Get the whole root system, or it resprouts.

   Dried, dead brush still causes a rash. Bag it for the trash and never burn it. Hire a professional for large stands.

3. Goats or sheep for small areas Natural enemies

   Goats and sheep will eat poison oak and can knock back small patches when grazed there repeatedly.

   Their coats can carry the oil to people.

4. Spot-treat with triclopyr or glyphosate Conventional spray

   Spray leaves in late spring or early summer while it is actively growing, or paint a freshly cut stump right away. Re-treat when sprouts regrow.

   Read and follow the label. Many lawn and brush herbicides also kill garden plants, so keep spray and drift off anything you want to keep. Near streams, only certain aquatic formulations are allowed.

Uses, wildlife and pets

For wildlife

Birds eat the berries, and deer browse the leaves.

Pets

The ASPCA lists poison oak as non-toxic to dogs, cats and horses, but pets can carry the oil on their fur to people. Bathe a pet that brushed through it while wearing gloves.