Flora of North America species comparison

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Ceanothus impressus

Ceanothus pumilus

Santa Barbara ceanothus

dwarf ceanothus, Siskiyou mat
Habit Shrubs, evergreen, 0.5–3 m. Stems erect, not rooting at nodes; branchlets brown, not thorn-tipped, round in cross section, flexible, puberulent. Shrubs, 0.1–0.4 m, matlike to moundlike.
Stems

prostrate to spreading, sometimes rooting at proximal nodes;

branchlets reddish brown, flexible to ± rigid, tomentulose.
Leaves

petiole 0–4 mm;

blade ± flat to strongly cupped, oblong, elliptic, or suborbiculate, 5–20(–25) × 2.5–17(–20) mm, base rounded, margins serrulate, thick to weakly or strongly revolute, teeth 11–29, apex obtuse to rounded, abaxial surface pale green, villosulous, adaxial surface dark to medium green, sparsely puberulent, not glandular papillate; pinnately veined, veins furrowed.

not fascicled;

petiole 1–2 mm;

blade flat to ± cupped, slightly folded lengthwise adaxially, narrowly oblanceolate to narrowly oblong-oblanceolate, 5–15 × 3–6 mm, base cuneate, margins thick to ± revolute, usually denticulate near apex, sometimes entire, teeth (0 or) 2–3, apex usually truncate, sometimes obtuse, abaxial surface pale green, sparsely strigillose to glabrous, adaxial surface green to grayish green, dull, glabrous, sometimes glaucous.
Inflorescences

axillary or terminal, umbel-like to racemelike, 1.2–3.5 cm.

axillary, 1–1.7 cm.
Flowers

sepals, petals, and nectary blue.

sepals, petals, and nectary pale blue to lavender.
Capsules

3–4 mm wide, lobed;

valves smooth, crested.

4–6 mm wide, lobed;

valves smooth, horns subapical, minute or weakly developed bulges, intermediate ridges absent.
2n

= 24.

Ceanothus impressus

Ceanothus pumilus
Phenology Flowering Apr–Jun.
Habitat Rocky soils derived from serpentine, open flats and slopes, chaparral, conifer forests.
Elevation 100–2200 m. (300–7200 ft.)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Ceanothus pumilus is endemic to the Klamath Mountains, where it occurs strictly on serpentine soils; it sometimes has been confused with C. arcuatus and C. prostratus, from which it differs principally by its oblanceolate to oblong-lanceolate leaf blades with a truncate, 3-toothed apex.

Hybrids between Ceanothus pumilus and C. cuneatus have been called C. ×humboldtensis Roof.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Leaf blades oblong to elliptic, 5–11(–14) × 2.5–8(–12) mm, strongly cupped, margins strongly revolute.
var. impressus
1. Leaf blades widely elliptic to suborbiculate, 11–20(–25) × 7–17(–20) mm, ± flat to cupped, margins thick to weakly revolute.
var. nipomensis
Source FNA vol. 12, p. 91. FNA vol. 12, p. 105.
Parent taxa Rhamnaceae > Ceanothus > subg. Ceanothus Rhamnaceae > Ceanothus > subg. Cerastes
Sibling taxa
C. americanus, C. arboreus, C. arcuatus, C. confusus, C. cordulatus, C. crassifolius, C. cuneatus, C. cyaneus, C. dentatus, C. divergens, C. diversifolius, C. fendleri, C. ferrisiae, C. foliosus, C. fresnensis, C. gloriosus, C. griseus, C. hearstiorum, C. herbaceus, C. incanus, C. integerrimus, C. jepsonii, C. lemmonii, C. leucodermis, C. maritimus, C. martini, C. masonii, C. megacarpus, C. microphyllus, C. oliganthus, C. ophiochilus, C. otayensis, C. palmeri, C. papillosus, C. parryi, C. parvifolius, C. pauciflorus, C. perplexans, C. pinetorum, C. prostratus, C. pumilus, C. purpureus, C. roderickii, C. sanguineus, C. sonomensis, C. spinosus, C. thyrsiflorus, C. tomentosus, C. velutinus, C. verrucosus
C. americanus, C. arboreus, C. arcuatus, C. confusus, C. cordulatus, C. crassifolius, C. cuneatus, C. cyaneus, C. dentatus, C. divergens, C. diversifolius, C. fendleri, C. ferrisiae, C. foliosus, C. fresnensis, C. gloriosus, C. griseus, C. hearstiorum, C. herbaceus, C. impressus, C. incanus, C. integerrimus, C. jepsonii, C. lemmonii, C. leucodermis, C. maritimus, C. martini, C. masonii, C. megacarpus, C. microphyllus, C. oliganthus, C. ophiochilus, C. otayensis, C. palmeri, C. papillosus, C. parryi, C. parvifolius, C. pauciflorus, C. perplexans, C. pinetorum, C. prostratus, C. purpureus, C. roderickii, C. sanguineus, C. sonomensis, C. spinosus, C. thyrsiflorus, C. tomentosus, C. velutinus, C. verrucosus
Subordinate taxa
C. impressus var. impressus, C. impressus var. nipomensis
Synonyms C. prostratus var. profugus
Name authority Trelease: Proc. Calif. Acad. Sci., ser. 2, 1: 112. (1888) Greene: Erythea 1: 149. (1893)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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