Willow Primer for the San Gabriel Mountains


Trees and shrubs in the willow genus are identified by long, slender leaves growing alternately along the stem and by a single, large scale capping the flower bud in winter. The flowers are catkins; male and female flowers grow on separate plants. In the San Gabriel Mountains, willows grow where there is moisture, often indicating underground water courses in the canyons or seeps and springs on the mountainsides. These trees and shrubs provide some of our best and brightest, most long-lasting fall color.

View a panoramic picture of an assortment of willows and other trees in fall at Chino Hills State Park.


What to look for

You need only a twig with a winter bud scale and a leaf to identify the willows below ~5500 feet elevation. Above that elevation in the San Gabriel Mountains, you need flowers to distinguish two of the species. Most of our willows are not totally deciduous. If you find one that is, look on the ground for a fallen leaf.

This primer includes all cismontane southern California species found below ~5500 feet, as well as Salix scouleriana, the most common species found above that elevation. It includes all species found in the San Gabriel Mountains, with the possible exception of Salix melanopsis, vouchered from three locations (Chilao, Swartout Valley, and near the head of San Antonio Canyon) from 5300 to 7500 feet. The Jepson Manual does not place this species in southern California; we speculate that these might be misidentified S. exigua, since these two species are distinguished only by minute details in the Munz key.

Simple willow key following the Jepson Manual:

Winter bud scale is very sharply pointed and overlapping
Leaf is not glaucous (white) underneath = Salix gooddingii, black willow
Leaf is glaucous (white) underneath = Salix laevigata, red willow
Winter bud scale is fused into a cylinder and blunt tipped
Petiole (leaf stalk) with glands at the base of the blade = Salix lucida var. lasiandra, shining willow
Petiole without glands
Leaf is linear, generally less than 1 cm wide (1 cm is about the width of the fingernail on the little finger of most adults) = Salix exigua, narrowleaf willow
Leaf more than 1 cm wide
All elevations; ovary glabrous; thin edge of leaf margin flat to moderately minutely rolled under = Salix lasiolepis, arroyo willow
Elevations above 5500 feet; ovary hairy; thin edge of leaf margin moderately to strongly minutely rolled under = Salix scouleriana, Scouler's willow


Salix exigua (including Salix hindsiana); another link

Salix gooddingii ; another link

Salix laevigata

Salix lasiolepis; another link

Salix lucida ssp. lasiandra (=Salix lasiandra)

Salix scouleriana

Sources and Other Web Information

Plants of Southern California: Salix: Key to Willows of Coastal Southern California Below 6000 Feet Elevation

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

A Field Guide to Western Trees by George A. Petrides, Houghton Mifflin Co., 1992.

The Jepson Manual Higher Plants of California edited by James C. Hickman, University of California Press, 1993.

Go to: Keys to Identifying Selected Plant Groups in the SGM

Copyright © 2000-2007 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:
Comments and feedback: Jane Strong | Tom Chester
Updated 14 January 2007