Flora of North America species comparison

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Ceanothus incanus

Ceanothus jepsonii

coast whitethorn

Jepson ceanothus, Jepson's ceanothus, musk brush
Habit 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. Shrubs, 0.5–1.5 m. Stems erect to ascending, not rooting at nodes; branchlets reddish to grayish brown, rigid, puberulent, glabrescent.
Leaves

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.

not fascicled, deflexed;

petiole 0–2 mm;

blade ± cupped, slightly folded lengthwise adaxially, elliptic to ± oblong, 10–20 × 5–13 mm, base rounded, margins thick or slightly revolute, spinose-dentate, teeth 7–11, apex rounded or sharply acute, abaxial surface pale yellowish green, glabrous, adaxial surface pale green, glabrous.
Inflorescences

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

axillary or terminal, 1–2 cm.
Flowers

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

sepals and petals (5–)6(–8), usually blue to lavender or white, rarely pink;

nectary blue;

stamens (5–)6(–8).
Capsules

4–5 mm wide, ± lobed;

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

5–7 mm wide, lobed;

valves rugose, horns subapical, prominent, thick, erect, rugose, intermediate ridges present.
2n

= 24.

Ceanothus incanus

Ceanothus jepsonii
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

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.)

Varieties 2 (2 in the flora).

Ceanothus jepsonii, composed of two, allopatric varieties, is the only species with mostly six (rarely eight) sepals and petals, and cymules reduced to solitary flowers (M. A. Nobs 1963). T. M. Hardig et al. (2000) provided evidence showing that the two varieties may not form a monophyletic group. H. McMinn (1942) and Nobs (1963) reported putative hybrids with C. cuneatus and C. prostratus.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Sepals and petals usually pale blue to lavender, rarely pink or white; capsules globose.
var. jepsonii
1. Sepals and petals white; capsules ± oblong.
var. albiflorus
Source FNA vol. 12, p. 86. FNA vol. 12, p. 106.
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. 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
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. 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. jepsonii var. albiflorus, C. jepsonii var. jepsonii
Name authority Torrey & A. Gray: Fl. N. Amer. 1: 265. (1838) Greene: Man. Bot. San Francisco, 78. (1894)
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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