Ceanothus integerrimus

Deer brush

Rhamnaceae

The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Magnoliophyta (flowering plants). Class - Magnoliopsida (dicotyledons). Subclass - Rosidae. Order - Rhamnales. Family - Rhamnaceae (buckthorn). Genus - Ceanothus L. Species - Ceanothus parvifolius (S. Watson) Trel.

Ecology: Deer brush is a nitrogen-fixing shrub that grows in open sun to partial shade. When overtopped by trees, deer brush dies out. It is typically successional after fire, landslide, logging, mining, or other stand-replacing events. Deer brush seedlings establish in the initial postdisturbance community. If fire or other disturbance is frequent enough to prevent conifers from establishing a canopy, deer brush and other shrubs may occupy a site indefinitely. Deer brush is a component of chaparral communities including Arizona chaparral. In the Cascade-Sierra Nevada cordillera, it is most common in montane chaparral but also occurs in upper, moister portions of lower-elevation chaparral types such as chamise (Adenostoma fasciculatum) and manzanita (Arctostaphylos spp.). Deer brush grows in the understories of conifer and oak (Quercus spp.) communities and in scattered patches within timberlands and woodlands. Patches of decadent deer brush are common in open Coulter pine (Pinus coulteri) stands. Deer brush often dominates early successional stages of low-elevation conifer communities.

Identification

Habit: Plant occasionally tree-like, open, < 4 m. Stem: ascending to erect; twigs flexible, not thorn-like, generally green. Leaf: alternate, deciduous; stipules scale-like; petiole 3--12 mm; blade 15--53 mm, 10--45 mm wide, thin, flat, lanceolate to widely ovate, adaxially dull green, glabrous to puberulent, abaxially pale green, glabrous to sparsely short-hairy, 1--3-ribbed from base, margin generally entire. Inflorescence: panicle-like, 4--20 cm. Flower: white to blue (pink). Fruit: 4--6.5 mm wide, sticky, smooth to bulged or +- 3-ridged distally; horns 0.

Threats

Fire effects: Deer brush sprouts from the root crown after fire, but sprouting response may be weak. Sprouts on older plants have died in their first year even when watered in summer. Mature deer brush is usually killed by fire. A few plants may be only top-killed. Most soil-stored deer brush seed survives fire. Seed in heavy duff may be killed by moderate to severe fire.

Reproduction

Seed reproduction: Deer brush first produces seed at about 4 years of age. Ripe seed is forcibly ejected from the capsule when the capsule dries and splits. Deer brush is a seed banking species. Seed is stored in extremely high densities in duff and the upper few centimeters of mineral soil. Viability of deer brush seed is generally high, and the seed is long-lived.

Seedling germination and establishment: Seed is dormant until the hard seedcoat is scarified by fire or mechanical disturbance such as logging. Optimal temperatures for scarification range from 77-90 deg C. High-consumptive fire (> 90% of duff burned) kills most seed in duff, but most seed in mineral soil survives. Best establishment occurs with seed in bare mineral soil. Nearly all seedling establishment occurs in the first postfire spring; establishment after the second postfire year is rare.

Vegetative reproduction: Sprouts grow more rapidly than seedlings, reaching a height of 76 cm or more in their first year. When deer brush plants are top-killed before they become decadent, roots remain alive, and root crowns retain the ability to sprout for years beyond the 35-year life expectancy of other stem tissue. Without periodic top-kill, root systems and root crowns of decadent plants die.

Species Distribution

Citation

USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
Photo credit: Gary A. Monroe.

The Jepson Herbarium
The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA.

Burke Museum of Natural History and Culture
Burke Museum. 2016 [Online]. University of Washington.