Flora of North America species comparison

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Ceanothus impressus

Ceanothus incanus

Santa Barbara ceanothus

coast whitethorn
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, evergreen, 1–4 m. Stems erect, not rooting at nodes; branchlets light gray, glaucous, thorn-tipped or not, round or slightly angled in cross section, rigid, puberulent, glabrescent.
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 3–12 mm;

blade flat, elliptic, ovate, or suborbiculate, 20–60 × 10–30 mm, base rounded or subcordate, margins entire, sometimes minutely glandular-denticulate above middle, glands 26–52, apex obtuse, abaxial surface pale green, appressed-puberulent, glabrescent, adaxial surface grayish green, dull, glabrate; 3-veined from base.
Inflorescences

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

axillary, usually paniclelike, sometimes racemelike, 3–6 cm.
Flowers

sepals, petals, and nectary blue.

sepals, petals, and nectary usually white to cream, sometimes pink.
Capsules

3–4 mm wide, lobed;

valves smooth, crested.

4–5 mm wide, ± lobed;

valves rugose, viscid when young, not or weakly crested.
2n

= 24.

Ceanothus impressus

Ceanothus incanus
Phenology Flowering Apr–Jun.
Habitat Flats, slopes, chaparral, open sites in conifer and mixed evergreen forests.
Elevation 60–1000 m. (200–3300 ft.)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

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

Ceanothus incanus is restricted to the Klamath and Santa Cruz mountains and North Coast Ranges of California. Some populations are evidently polymorphic for the presence of thorn-tipped or non-thorn-tipped branchlets (F. K. Klein 1970). Putative hybrids with C. papillosus and C. parryi have been reported (H. McMinn 1944); hybrids with C. thyrsiflorus have been called C. ×vanrensselaeri 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. 86.
Parent taxa Rhamnaceae > Ceanothus > subg. Ceanothus Rhamnaceae > Ceanothus > subg. Ceanothus
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. 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
Subordinate taxa
C. impressus var. impressus, C. impressus var. nipomensis
Name authority Trelease: Proc. Calif. Acad. Sci., ser. 2, 1: 112. (1888) Torrey & A. Gray: Fl. N. Amer. 1: 265. (1838)
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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