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Stem Identification

 The leaflets of poison-oak usually occur in threes. However, the leaflets grow in a confusing variety of sizes, colors and shapes. Also, the leaflets grow so closely together it is difficult to see triplets. From November through January much of the poison-oak is dormant there are no leaflets to look at. This brush is dangerous to touch. Dead plants may also be poisonous.

Identification of poison-oak by looking at its stems is faster, easier and simpler. The stem characteristics are recommended for detection are:

1.     Branching,

2.     Thickness,

3.     Stiffness, and

4.   You can check your identifications by confirming the presence of aerial roots and black spots, until youre confident.

Branching:  The side branches are scattered along the main stem; they never come off the main stem opposite each other. They always come off the main stem at a sharp angle - about 70 degrees but never at 90 degrees.

Thickness:  1/8 to 1/4 inch and very uniformly tapered for the last three to six feet in all sites, except shady ones, where they are about 1/16 inch.

Stiffness:  At most sites you can feel poison-oak press against your pants. If you push through it, side branches break. In shady sites poison-oak is wiry, like a car antenna.

It may help to see, or even collect small samples of, contrasting plant types. For example, virgins bower is oppositely branched, at 90 degrees to the main stem. Coyote bush branches at acute angles, like 25 to 40 degrees; it tapers irregularly. Coast live oak tapers rapidly, about a inch per foot; it is so stiff people cant push through it.

 

All content copyright Dr. Curt Beebe. Please do not use without permission.