FOLIAGE

This Section of the web site begins with an article on the Arrangement of leaves on the stem. This “phylotaxy” is 3/8 officially (Gillis), but measures 2/5 on many specimens in the Morro Bay area.

Then I describe what happens to the average leaf in the different Seasons. At sea level dormancy is broken in early February, and for five weeks where there is poison-oak the foliage appears reddish as the new leaves emerge. There follows a more subtle two or three week period where the average leaf is lighter green than the surrounding vegetation. These changes are documented more fully in the following article on Development of a typical plant.

In April and May all the plant foliage looks the same. Then the poison-oak begins to drop its foliage, and again at this stage the foliage stands out. These changes are documented more fully in the article on Death. By mid-October involution is complete and the stems are again dormant.

So far we have dealt with only the average leaf. There is a lot of Variation from one plant to the next – so much variation that the species name for poison-oak is diversilobum. I deal with the variation in leaf morphology under the headings Genetic, Light, Stem Growth, Soil, and Male vs Female.