Flora of North America species comparison

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Ceanothus papillosus

Ceanothus pauciflorus

wartleaf ceanothus

desert buckbrush, desert buckthorn, Mojave ceanothus
Habit Shrubs, evergreen, 1–5 m. Stems erect to ascending, not rooting at nodes; branchlets green to reddish brown, not thorn-tipped, round in cross section, ± flexible to rigid, densely tomentulose. Shrubs, 0.2–2 m, sometimes moundlike.
Stems

erect or weakly ascending to spreading, not rooting at nodes;

branchlets light gray to ashy gray, rigid, puberulent to tomentulose, hairs curly or wavy, glabrescent.
Leaves

petiole 1–3 mm;

blade cupped to flat, linear, narrowly oblong, or oblong-elliptic, 12–50 × 6–15 mm, base obtuse to rounded, margins minutely glandular-denticulate, revolute, glands 17–31, apex obtuse, truncate, or retuse, abaxial surface pale green, densely villosulous to tomentulose, adaxial surface dark green, sparsely puberulent and glandular-papillate; pinnately veined.

not fascicled;

petiole (0–)1–3 mm;

blade flat to ± cupped, elliptic, oblong-elliptic, obovate, or suborbiculate, 5–15(–20) × 3–14(–15) mm, base cuneate to rounded, margins thick, not revolute, entire or remotely denticulate, teeth 1–5(–7), apex acute to ± truncate, abaxial surface pale green to grayish green, glabrate or puberulent, hairs curly or wavy, glabrescent, adaxial surface grayish green, puberulent, hairs curly or wavy, glabrescent.
Inflorescences

axillary or terminal, racemelike, 2–8 cm.

axillary, rarely racemelike, 0.7–3 cm.
Flowers

sepals, petals, and nectary deep blue.

sepals and petals white to cream, sometimes pale blue or lavender;

nectary yellowish green, brown, or blue.
Capsules

2–3 mm wide, lobed;

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

3.5–6 mm wide, not, or sometimes weakly, lobed;

valves smooth, horns lateral, prominent to minute or absent, spreading, intermediate ridges absent.
2n

= 24.

Ceanothus papillosus

Ceanothus pauciflorus
Phenology Flowering Mar–May. Flowering Feb–May.
Habitat Rocky ridges, slopes, and flats, chaparral, mixed evergreen forests. Rocky slopes, ridges, alluvial fans, sagebrush and montane shrublands, pinyon and/or juniper and montane conifer woodlands.
Elevation 20–1500 m. (100–4900 ft.) 900–2900.
Distribution
from FNA
CA; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CA; NM; NV; TX; UT; n Mexico; c Mexico
[WildflowerSearch map]
[BONAP county map]
Discussion

Ceanothus papillosus occurs in the Coast Ranges from San Francisco Bay south to the Santa Ynez Mountains, Ventura County, with disjunct populations in the Santa Ana Mountains, California, and Cerro Bola, in northern Baja California. The name C. papillosus var. roweanus was originally applied to low-growing plants with ascending to spreading, arcuate branches (H. McMinn 1939). M. Van Rensselaer and McMinn (1942) later emended the circumscription to include plants with linear leaves and retuse to truncate leaf apices, but these are found throughout the range of the species. Leaves with obtuse to truncate or retuse leaf apices also can be found on the same plant. Putative hybrids with C. integerrimus and C. oliganthus have been documented (McMinn 1944). Hybrids with C. thyrsiflorus have been named C. ×regius (Jepson) McMinn. Some putatively advanced generation hybrids have narrowly elliptic, weakly papillate leaves with obtuse apices, and sometimes have been misinterpreted as belonging to C. papillosus.

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

Ceanothus pauciflorus as circumscribed here includes plants having flat to cupped leaf blades with a sparse to dense but not intertwined indumentum composed of short curly or wavy hairs, at least when young; this indumentum also occurs on the petiole and ultimate branchlets. Such plants in the United States have been treated either as C. greggii or C. vestitus (M. Van Rensselaer and H. McMinn 1942). However, R. McVaugh (1998) and D. O. Burge and K. Zhukovsky (2013) provided evidence that they should be treated as C. pauciflorus. Specimens from the desert slopes of the Sierra Nevada and San Bernardino Mountains, California, and a few scattered localities in western Arizona, have leaves similar in shape and dentation to those of C. perplexans, suggesting local hybridization.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 12, p. 92. FNA vol. 12, p. 107.
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. 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. 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. 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. papillosus subsp. roweanus, C. papillosus var. roweanus C. greggii, C. greggii var. franklinii, C. vestitus
Name authority Torrey & A. Gray: Fl. N. Amer. 1: 268. (1838) de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 2: 33. (1825)
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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