Bull. Torrey Bot. Club 25: 304. 1898.
Shrubs, evergreen, 1-4 m. Stems ± dimorphic, with elongate primary and short or somewhat elongate axillary shoots. Bark of 2d-year stems grayish purple, glabrous. Bud-scales 2-4 mm, deciduous. Spines absent. Leaves 3-9-foliolate; petioles 0.1-0.5 cm. Leaflet blades thick and rigid; surfaces abaxially dull, papillose, adaxially dull, glaucous; terminal leaflet stalked in most leaves, blade 1.5-3.8 × 0.5-1.1 cm, 2-5 times as long as wide; lateral leaflet blades oblong-ovate to ovate or lanceolate, 1 (-3) -veined from base, base acute to obtuse, rarely subtruncate, margins undulate or crispate, toothed or lobed, with 2-4 teeth 1-4 mm high tipped with spines to 1.2-2 × 0.2-0.3 mm, apex narrowly acute or acuminate. Inflorescences racemose, lax, 3-7-flowered, 1.5–4.5 cm; bracteoles membranous, apex acuminate. Flowers: anther-filaments without distal pair of recurved lateral teeth. Berries purplish red, glaucous, spheric or short-ellipsoid, 5-8 mm, juicy, solid.
Phenology: Flowering winter–spring (Feb–Jun).
Habitat: Slopes and flats in desert shrubland, desert grassland, and dry oak woodland
Elevation: 900-2300 m
Ariz., Calif., Colo., Nev., N.Mex., Tex., Mexico (Sonora)
Typical populations of Berberis haematocarpa (with narrowly ovate or lanceolate leaflets and small, juicy, deep red berries) and B. fremontii (with ovate or orbiculate leaflets and large, dry, inflated, yellowish or brownish berries) are easily distinguished. These characteristics are not always well correlated, however, and intermediate populations, showing different combinations of leaflet shape and berry size, color, and inflation, are known.
Berberis haematocarpa is susceptible to infection by Puccinia graminis.
"thick" is not a number.