Ceanothus Subgenera
by Bruce Homer-Smith

Ceanothus can be split into two groups that have distinctive characteristics and don’t interbreed – subgenus Ceanothus and subgenus Cerastes.

Here’s what to look for to distinguish which subgenera you’re working with.

Ceanothus subgenus

Cerastes subgenus

Alternate leaves with deciduous scaly stipules

Hairy Ceanothus – photo by Keir Morse

Opposite leaves with persistent, corky stipules

Buck Brush – drawing © John Muir Laws

Leaves often have 3 major veins that start at the base. Small-leaved species have a single central vein.

Blue Blossom – photo by Zoya Akulova-Barlow

Underside of leaf show veins in a herringbone pattern.

Buck Brush – photo by Steve Matson

Leaves are mostly deciduous and are not leathery. Plants are often large, often tree-like.

Island Ceanothus – photo by Zoya Akulova-Barlow

Leaves are mostly evergreen and leathery. Shrubs are often dense and compact.

Jepson Ceanothus – photo © Neil Kramer

Flowers are mostly in elongated clusters

Deer Brush – photo © Jeff Bisbee

Flowers are in rounded clusters

Deer Brush – photo by Wilde Legard

3-part seed pods are smooth and without horns

Blueblossom – photo by Zoya Akulova-Barlow

3-part seed pods have horns

Single taproot

Spreading roots.

Native in the California Floristic Province and beyond.

Native only in the California Floristic Province.

Now you’ve got something to look for when you see these beauties in the field. Have fun with them!

Corrections/Comments: bruce@PlantID.net