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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.
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.
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.
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