Ceanothus prostratus

Bentham
Pl. Hartw., 302. 1849.
IllustratedEndemic
Treatment appears in FNA Volume 12. Treatment on page 104. Mentioned on page 84, 87, 95, 100, 106.

Shrubs, 0.1–0.3 m, matlike to moundlike. Stems prostrate, spreading, or ascending, rooting at distal nodes; branchlets reddish brown, ± flexible, puberulent, glabrescent. Leaves not fascicled, crowded, usually longer than internodes and obscuring them; petiole 1–3 mm; blade flat to ± cupped, elliptic to obovate, 6–30 × 4–16 mm, base cuneate, margins sometimes thick, not revolute, sometimes wavy, sharply dentate to spinose-dentate, teeth 3–9, apex rounded, abaxial surface pale green, glabrous except sparsely strigillose on veins, adaxial surface dark green, shiny, glabrate. Inflorescences axillary, 0.9–2 cm. Flowers: sepals, petals, and nectary pale to deep blue or purplish blue. Capsules 6–9 mm wide, lobed; valves smooth to rugulose, horns subapical, prominent, erect or spreading, rugose or not, intermediate ridges present. 2n = 24.

Distribution

V12 333-distribution-map.jpg

Calif., Idaho, Nev., Oreg., Wash.

Discussion

Varieties 2 (2 in the flora).

Putative hybrids between Ceanothus prostratus and C. velutinus var. velutinus, named C. ×rugosus, have been reported from northeastern California (H. McMinn 1944). A rare putative hybrid between C. prostratus and C. cordulatus in the Lake Tahoe basin has been named C. ×serrulatus. Both C. ×rugosus and C. ×serrulatus are intersubgeneric hybrids. Formally named hybrids between C. prostratus and C. cuneatus var. cuneatus include C. ×flexilis and possibly C. ×connivens, but the latter could have C. fresnensis as one of the parents rather than C. prostratus.

Selected References

None.

Key

1 Leaf blades flat, margins not wavy, teeth usually 3–5(–7); capsule horns erect. Ceanothus prostratus var. prostratus
1 Leaf blades slightly folded lengthwise adaxially, margins ± wavy, teeth 5–9; capsule horns spreading. Ceanothus prostratus var. occidentalis