The Seasonal Appearance of Poison-Oak
An Overview

(The changes shown occur two weeks later at 1,000 feet elevation.)

Winter
Christmas to February 7 in Morro Bay

Most of the poison-oak is leafless. Poison-oak plants are either male or female. This is a female; it has panicles (fruit stalks) and a few berries still attached. The 70 degree branching angle is highly characteristic of poison-oak.

However, each warm spell brings forth a sparse crop of tiny, light green leaves and blossoms.

Spring

Around March 1st, crop after crop of new leaves are appearing. The reddish color of the emerging leaves is characteristic. The color changes to light green in three to ten days.

By late May, the canopy is complete: thick, and dark green.

Summer

In favorable conditions, poison-oak keeps its leaves, and most of its color, all summer long. Here, the medium green of the poison-oak contrasts with
          1. the dark green of coyote brush;
          b. the chocolate color of sticky monkey flower; and
          c. the grey of California sage.

When water becomes scarce, the leaves turn lighter green; then pale red; and finally are shed. Water loss is greatly reduced, while photosynthesis continues at a low rate underneath the bark. This is a "dry deciduous" behavior.

Fall

When temperatures drop low enough, the Fall color change occurs, and the remaining foliage is shed.