Flora of North America species comparison

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Ceanothus thyrsiflorus

Ceanothus griseus

blue blossom, blue blossom ceanothus

Carmel ceanothus
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, 0.5–4 m. Stems erect, ascending to arcuate, rarely prostrate, not rooting at nodes; branchlets green, not thorn-tipped, angled in cross section, flexible, sparsely puberulent or glabrous.
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 5–10 mm;

blade flat to cupped, ovate to suborbiculate, 10–45 × 10–30 mm, base obtuse to rounded, margins denticulate, ± revolute, teeth 21–45, apex obtuse to rounded, abaxial surface pale green, puberulent to densely villosulous, veins prominently raised, puberulent to villosulous, adaxial surface dark green, glabrate; 3-veined from base.
Inflorescences

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

axillary, paniclelike, 2–7 cm.
Flowers

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

sepals, petals, and nectary blue.
Capsules

3–4 mm wide, weakly lobed;

valves smooth, viscid, not crested.

3–4 mm wide, weakly lobed at apex;

valves smooth, viscid, not crested.
2n

= 24.

Ceanothus thyrsiflorus

Ceanothus griseus
Phenology Flowering Mar–Jun. Flowering Mar–Jun.
Habitat Sandy or rocky flats and slopes, maritime chaparral, open sites in mixed evergreen and conifer forests. Sandy or rocky flats and slopes, maritime chaparral, open sites in pine and cypress forests.
Elevation 10–600 m. (0–2000 ft.) 10–200 m. (0–700 ft.)
Distribution
from FNA
CA; OR; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
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.)

Ceanothus griseus is distributed along the coast from Mendocino County south to Santa Barbara County. Plants with incompletely revolute leaf margins and abaxial surfaces intermediate or similar to those of C. thyrsiflorus are encountered frequently. Whether this pattern is a result of primary or secondary intergradation is not known. Prostrate plants with wide elliptic leaves have been called C. griseus var. horizontalis McMinn; they retain their stature under cultivation. Putative hybrids with C. dentatus have been named C. ×lobbianus Hooker (M. Van Rensselaer and H. McMinn 1942). Ceanothus ×veitchianus Hooker is a rare intersubgeneric hybrid between C. griseus and C. rigidus, first collected by William Lobb near Monterey in 1853, that is cultivated in Great Britain as an ornamental.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 12, p. 90. FNA vol. 12, p. 91.
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. 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. thyrsiflorus, C. tomentosus, C. velutinus, C. verrucosus
Synonyms C. thyrsiflorus var. chandleri, C. thyrsiflorus var. repens C. thyrsiflorus var. griseus, C. griseus var. horizontalis
Name authority Eschscholtz: Mém. Acad. Imp. Sci. St. Pétersbourg Hist. Acad. 10: 285. (1826) — (as thyrsiflora) (Trelease) McMinn: in M. van Rensselaer and H. McMinn, Ceanothus, 210. (1942)
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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