Flora of North America species comparison

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Ceanothus diversifolius

Ceanothus arcuatus

pine mat

arching ceanothus
Habit Shrubs, evergreen, 0.2–0.3(–0.5) m, matlike. Shrubs, 0.3–0.8 m, moundlike.
Stems

spreading, sometimes rooting at nodes;

branchlets green, sometimes tinged red, not thorn-tipped, usually round, sometimes angled, in cross section, flexible, puberulent.

ascending or spreading, not rooting at nodes;

branchlets brown to grayish brown, ± rigid, tomentulose, glabrescent.
Leaves

petiole 3–11 mm;

blade flat, elliptic to widely ovate, 12–45 × 6–20 mm, base obtuse to rounded, margins serrulate to denticulate, not revolute, usually not wavy, sometimes wavy, teeth 27–42, apex ± obtuse to rounded, abaxial surface pale green, pilosulous, adaxial surface green, pilosulous; usually pinnately veined, rarely 3-veined from base.

sometimes fascicled, axillary short shoots ascending to spreading;

petiole 1–2 mm;

blade flat, elliptic to oblanceolate, 4–10 × 2–5 mm, base rounded, margins thick, not revolute, usually entire, rarely denticulate near apex, teeth 1–3, apex rounded to obtuse, abaxial surface green to pale green, glabrate, adaxial surface pale green, glabrous.
Inflorescences

axillary, umbel-like to racemelike, 1.3–4 cm.

axillary or terminal, 0.8–2.5 cm.
Flowers

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

sepals and petals white to pale blue;

nectary pale blue or yellow tinged.
Capsules

4–5 mm wide, weakly lobed near apex;

valves smooth, crested.

4–6 mm wide, not to weakly lobed;

valves smooth to rugulose, horns subapical, prominent, erect, intermediate ridges absent.

Ceanothus diversifolius

Ceanothus arcuatus
Phenology Flowering Apr–Jun. Flowering May–Jun.
Habitat Well-drained slopes and canyons, open to shaded sites, mixed evergreen and conifer forests. Granitic or serpentine soils, conifer forests.
Elevation 700–2300 m. (2300–7500 ft.) 900–2300 m. (3000–7500 ft.)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; OR
[BONAP county map]
Discussion

Ceanothus diversifolius occurs in the North Coast Ranges and the western slopes of the Cascade Range and the Sierra Nevada; it often forms mats to two meters wide. Marginal teeth on young leaves are notable in having more or less persistent, narrowly conic glands, not seen elsewhere in Ceanothus.

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

Ceanothus arcuatus was explicitly described as a species by McMinn but inexplicably treated as a hybrid between C. fresnensis and C. cuneatus by P. A. Munz (1959). Munz may have been influenced by McMinn’s hypothesis that C. arcuatus was derived through hybridization between the two species. Some specimens from the Klamath Mountains have been either interpreted as C. cuneatus or misidentified as hybrids between C. pumilus and C. cuneatus. Populations of C. arcuatus are relatively uniform throughout their geographic distribution and often represent the dominant understory shrub in conifer forests of the Klamath Mountains and Sierra Nevada. Ceanothus arcuatus occurs primarily on metamorphic substrates in the Klamath Mountains and the northern Sierra Nevada, but in the central Sierra Nevada (Nevada County south to Madera County), the most common substrate is granitic.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 12, p. 94. FNA vol. 12, p. 101.
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. 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. thyrsiflorus, C. tomentosus, C. velutinus, C. verrucosus
C. americanus, C. arboreus, 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. thyrsiflorus, C. tomentosus, C. velutinus, C. verrucosus
Synonyms C. decumbens
Name authority Kellogg: Proc. Calif. Acad. Sci. 1: 58. (1855) McMinn: in M. van Rensselaer and H. McMinn, Ceanothus, 247, fig. 82. (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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