Ceanothus Primer for the San Gabriel Mountains


Key
Descriptions
Glossary
Sources
Ceanothus are large, rounded shrubs with small, generally evergreen, leaves. They are covered with masses of white to blue lilac-like flowers in late winter through spring. Ceanothus sometimes form inpenetrable thickets in the chaparral, especially a few years after a fire.

A note about color: Colors of the flowers change with age, usually going from darker to lighter, i.e., bluer to whiter, in ceanothus. Color is also variable 1) by location, e.g., a shaded bloom would be darker, 2) by film used for the picture and the quality of development, and 3) by the viewer's tinted glasses! These variations apply to leaf color as well. Use the links provided under the descriptions to check your identification; they show some of the variations.

The number of records is a rough indicator of frequency. You are almost sure to see those with the largest number of observation records.

Key

1. The stem has stipules (small dark bumps) and leaves in pairs (opposite each other). Go to 2.
1'. The stem does not have stipules and the leaves are alternate. Go to 4.

2. The leaf is densely white-hairy underneath and the margins usually rolled under. It is Hoaryleaf Ceanothus Ceanothus crassifolius.
2'. The leaf is not densely white-hairy underneath and the margins are not rolled under. Go to 3.

3. The leaf is flat and the leaf margins are generally without teeth. It is Buck Brush Ceanothus cuneatus.
3'. The leaf is toothed; often cupped. It is Desert Ceanothus Ceanothus greggii.

4. The stem is rigid and spiny at the tip. Go to 5.
4'. The stem is flexible and usually not spiny. Go to 6.

5. The upper leaf surface is powdery, takes a thumbprint, and the trunk is white. It is Chaparral Whitethorn Ceanothus leucodermis.
5'. The leaf is blue-gray-green on both sides. It is Snow Brush Ceanothus cordulatus.

6. The leaf is toothed and hairy especially near the veins. It is Hairy Ceanothus Ceanothus oliganthus
6'. The leaf is smooth on the edge and deciduous. It is Deer Brush Ceanothus integerrimus

Descriptions

Ceanothus cordulatus Kellogg

Ceanothus crassifolius Torrey

Ceanothus cuneatus (Hook.) Nutt.

Ceanothus greggii A. Gray

Ceanothus integerrimus Hook. & Arn

Ceanothus leucodermis E. Greene

Ceanothus oliganthus Nutt.

Originally Ceanothus thyrsiflorus and Ceanothus palmeri were part of this list, but we have been unable to verify their presence.

Glossary

entire: the edge of the leaf is smooth, not toothed and not wavy

opposite leaves: leaves come in pairs along the stem, one on each side (not alternate)

spiny: having sharp, thin, thorny projections on the stems

stipules: swollen, dark, corky bumps flanking the leaf stalk where it comes out from the stem or branch

Sources

How To Identify SGM Ceanothus In The Winter

Description of Ceanothus along Barley Flats Trail

CalFlora Occurrence Database. A search for Ceanothus in Los Angeles County yielded 481 observation records for the San Gabriel Mountains.

Cliff Schmidt's Ceanothus key and species descriptions, which include geographic distributions of each species.

A California Flora by Philip A. Munz. University of California Press, 1968.

Native Shrubs of Southern California by Peter H. Raven. University of California Press, 1966.

Roadside Plants of Southern California by Thomas J. Belzer. Mountain Press Publishing Company, 1984.

Sierra Nevada Natural History by Tracy I. Storer and Robert L. Usinger. University of California Press, 1963.

Go to: Plants of the San Gabriel Mountains

Copyright © 2000-2006 by Jane Strong and Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to us at this source:
http://tchester.org/sgm/plants/ceanothus.html
Comments and feedback: Jane Strong | Tom Chester
Updated 13 February 2001 (one link updated 2 May 2006).