Home

Spreading the Word
Typical Appearances
Briefing
Prevention
First Aid
Medical Care
Identification
Stems
Reproduction
Foliage

The Basic            
Arrangement
Seasons
Development
Death
Variation            
Genetic
Light
Stem Growth
Soil
Male vs Female

Risk Management
Biochemistry
Anecdotes
Bibliography


Appendices

Dermatology
Anacardiaceae

About the Author

Foliage

Arrangement of Leaves

Their arrangement on the stem is sub-alternate: adjacent leaves come off the stem at 135 or 144 degree angles, so that every eighth or fifth leaf emerges from exactly the same side of the stem.

Immediately beyond the leaf is a blossom bud. And immediately beyond the blossom bud is a branch bud.

Three Leaflets     Branch

Each leaf stalk is curved, like a stalk of celery. So when the leaf falls off a curved c or v shaped scar is left.

Usually, each leaf stalk bears three leaflets. However, in my experience half an hour of searching turns up a plant which bears five leaflets per stalk, and more rarely four or two leaflets. There are reports in the literature of up to up to nine leaflets per stalk.

Variety

The side leaflets may be attached directly to the leaf stalk, or attached by a short stalk. If present, these side stalks are 3/16th of an inch long, or shorter.

The end leaflet has its own stalk, which is always longer than the side stalks. This distinguishes poison-oak from sugar bush, in which the end leaflet attaches directly to the leaf stalk. Sugar bush is non-poisonous, and grown from Lake Cachuma south.

The two side leaflets are approximately mirror images of each other. The end leaflet is roughly symmetric.

Three Leaflets

 

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