Arctostaphylos glauca Specimens With Cordate Leaves
Arctostaphylos glauca is said in the Jepson Manual to have leaves with a base that is rounded, truncate, or slightly lobed. Most online pictures show rounded to truncate bases, although one page shows two leaves with a cordate base.
In 1988, Andy Sanders found a handful of Arctostaphylos specimens on the Cactus Springs Trail in the Santa Rosa Mountains that have leaf bases for many of their leaves that are distinctly cordate. The specimens were glabrous, like A. glauca, but seemed sufficiently different that follow-up investigation was necessary to be sure of their species assignment. Hence on 17 October 2006, I surveyed all the manzanita specimens on this trail to try to understand these specimens.
A. glauca is the only manzanita species present on the trail west of Horsethief Creek on the trail (the only portion thoroughly surveyed for manzanitas), with literally hundreds of specimens found all along the trail. The plants are quite uniform in all properties other than the leaf bases, and are clearly A. glauca by the absence of a burl, the total absence of hairs in every part of the plant, the glaucous leaves, and the large sticky fruit. Many older plants show the arborescent stems typical of this species. Some younger plants on steep slopes have some stems that appear to be horizontal, as sometimes happens on such steep slopes.
It was immediately obvious in the field that the specimens with cordate leaves are found only in locations where the plants have their roots in permanent water. When I found the first such specimen, after examining a zillion specimens with non-cordate leaves, I also noticed flowing water for the first time.
The following map gives their locations, shown as small blue diamonds:
All these specimens are in drainages. The three easternmost specimens are located in the only area of the trail west of Horsethief Creek with permanent flowing surface water. The westernmost specimen is located in a drainage that has no permanent flowing surface water, but there is a cottonwood tree just upstream of it, indicating permanent water near the surface.
The following pictures give a sample of leaves from three different plants, with each plant on a separate row:
Differences in color are due to illumination; they were all the same color in the field, quite white-glaucous. Manzanita leaves are notorious for appearing with different colors under different illumination.
Copyright © 2006 by Tom Chester
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
Comments and feedback: Tom Chester
Last update: 19 October 2006