Flora of North America species comparison

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Ceanothus thyrsiflorus

Ceanothus oliganthus

blue blossom, blue blossom ceanothus

hairy ceanothus, jimbrush (var. sorediatus)
Habit Shrubs, sometimes arborescent, evergreen, 0.5–6 m. Stems erect, usually ascending to arcuate, rarely prostrate, not rooting at nodes; branchlets green, not thorn-tipped, angled in cross section, flexible, not tuberculate, sparsely puberulent or glabrous. Shrubs, sometimes arborescent, evergreen, 2–3(–6) m. Stems erect, not rooting at nodes; branchlets reddish brown or brown, usually not, sometimes weakly, thorn-tipped, usually round, sometimes ± angled in cross section, flexible to rigid, glabrous, puberulent, or villosulous.
Leaves

petiole 3–10 mm;

blade flat to cupped, elliptic to ovate, 10–40(–50) × 5–15(–20) mm, base obtuse to rounded, margins denticulate to serrulate, usually not revolute, sometimes incompletely revolute, teeth glandular, 23–48, apex obtuse, abaxial surface pale green, sparsely puberulent to villosulous or glabrate, veins prominently raised, puberulent to villosulous, adaxial surface dark green, glabrate; 3-veined from base.

petiole 3–8 mm;

blade flat, ovate to widely elliptic, 8–35 × 4–25 mm, base obtuse to subcordate, margins denticulate most of length, not revolute, teeth 19–71, apex obtuse, rounded, or acute, abaxial surface usually pale green, sometimes gray-green, sometimes glaucous, glabrate to hirtellous, adaxial surface dark green, villosulous, especially on the veins, or glabrate; 3-veined from base.
Inflorescences

terminal, usually racemelike, rarely paniclelike, 2.5–9 cm.

axillary, racemelike, 1.5–5.2 cm.
Flowers

sepals, petals, and nectary usually pale to deep blue, rarely white.

sepals, petals, and nectary usually pale to deep blue or purplish blue, rarely white.
Capsules

3–4 mm wide, weakly lobed;

valves smooth, viscid, not crested.

4–7 mm wide, lobed, ± depressed at apex;

valves smooth or rugose, viscid, crested or not.
2n

= 24.

Ceanothus thyrsiflorus

Ceanothus oliganthus
Phenology Flowering Mar–Jun.
Habitat Sandy or rocky flats and slopes, maritime chaparral, open sites in mixed evergreen and conifer forests.
Elevation 10–600 m. (0–2000 ft.)
Distribution
from FNA
CA; OR; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; nw Mexico
[WildflowerSearch map]
[BONAP county map]
Discussion

Ceanothus thyrsiflorus occurs along the coast from Coos County, Oregon, south to Santa Barbara County, California, and disjunctly near Eréndira, Baja California. A wide range of growth forms characterize this species and the closely related C. griseus, including plants ranging from almost prostrate to arborescent, sometimes with single trunks. Prostrate plants from several maritime bluffs along the California coast have been called C. thyrsiflorus var. repens McMinn; they retain their stature under cultivation. Named hybrids include C. ×regius (Jepson) McMinn (C. thyrsiflorus × C. papillosus) and C. ×vanrensselaeri Roof (C. thyrsiflorus × C. incanus). H. McMinn (1944) reported hybrids with C. foliosus.

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

Varieties 3 (3 in the flora).

M. Van Rensselaer and H. McMinn (1942) treated var. oliganthus and var. sorediatus as species, although they and R. F. Hoover (1970) discussed intergradation between the two forms throughout part of their distribution, especially in the southern Coast Ranges and Transverse Ranges of California.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Ovaries and nectaries pilosulous; capsules glabrescent, valves rugose, weakly crested dorsally.
var. orcuttii
1. Ovaries and nectaries glabrous; capsules glabrous, valves smooth, crested or not.
→ 2
2. Branchlets puberulent to villosulous; leaf blade adaxial surfaces usually villosulous, sometimes glabrate; capsule valves usually crested, sometimes not.
var. oliganthus
2. Branchlets glabrous to sparsely puberulent; leaf blade adaxial surfaces sparsely villosulous to glabrate; capsule valves usually not, sometimes weakly, crested.
var. sorediatus
Source FNA vol. 12, p. 90. FNA vol. 12, p. 88.
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. 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. pumilus, C. purpureus, C. roderickii, C. sanguineus, C. sonomensis, C. spinosus, 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. 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. oliganthus var. oliganthus, C. oliganthus var. orcuttii, C. oliganthus var. sorediatus
Synonyms C. thyrsiflorus var. chandleri, C. thyrsiflorus var. repens
Name authority Eschscholtz: Mém. Acad. Imp. Sci. St. Pétersbourg Hist. Acad. 10: 285. (1826) — (as thyrsiflora) Nuttall: in J. Torrey and A. Gray, Fl. N. Amer. 1: 266. (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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