Flora of North America species comparison

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Ceanothus thyrsiflorus

Rhamnaceae

blue blossom, blue blossom ceanothus

buckthorn family
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, trees, or woody vines, [herbs, annual or perennial], evergreen or deciduous, synoecious, dioecious, or polygamous [monoecious], sometimes armed with thorns or stipular spines.
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.

alternate, fascicled, clustered, or opposite, simple;

stipules present;

petiole present (absent in Condalia);

blade margins entire, serrate, serrulate, crenate, crenulate, dentate, or denticulate, sometimes spinose or spinulose;

venation pinnate (sometimes obscurely, appearing 1-veined) or 3[–5]-veined from base (acrodromous).
Inflorescences

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

bisexual or unisexual, axillary or terminal, fascicles, umbels, panicles, cymes, or thyrses (these sometimes spikelike, racemelike, or paniclelike), or flowers solitary.
Flowers

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

bisexual or unisexual;

perianth and androecium epigynous or perigynous [hypogynous];

hypanthium free or adnate to ovary proximally and free distally [absent];

sepals [3–]4–5(–8), distinct, valvate;

petals 0 or [3–]4–5(–8), distinct;

nectary present, intrastaminal, sometimes lining hypanthium;

stamens [3–]4–5(–8), opposite petals, distinct, adnate to petal bases;

anthers dehiscing by longitudinal slits;

pistil 1, 2–4-carpellate, ovary superior to inferior, (1–)2–4-locular, placentation basal;

ovules 1 per locule (2 per locule in Karwinskia), anatropous;

styles 1–4, connate proximally to completely;

stigmas 1–4.
Fruits

capsules, dehiscence loculicidal, schizocarps, samaras, or drupes.
Capsules

3–4 mm wide, weakly lobed;

valves smooth, viscid, not crested.

Seeds

1 (sometimes 2 in Karwinskia) per locule.
2n

= 24.

Ceanothus thyrsiflorus

Rhamnaceae
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]
North America; Mexico; Central America; South America; West Indies; Europe; Asia; Africa; Atlantic Islands; Indian Ocean Islands; Pacific Islands; Australia; mainly subtropical to tropical areas
[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.)

Genera 50–52, species 900–950 (15 genera, 105 species in the flora).

The fused, cuplike basal portion of the flower has been variously called a hypanthium (as here), floral cup, floral tube, and calyx tube.

The bark, leaves, and fruits of Frangula alnus, F. purshiana, and Rhamnus cathartica have been used as laxatives. Old World species of Rhamnus provide yellow and green dyes as well as drugs. Wood of some species (in Alphitonia Reissek ex Endlicher, Colubrina, Hovenia, and Ziziphus) is used for construction, high quality furniture, carving, lathe work, and musical instruments. Ziziphus mauritiana (Indian jujube) and Z. jujuba (common jujube) are commercially cultivated for edible fruit. Hovenia dulcis is grown for its edible, fleshy inflorescence stalks. Some species of Ceanothus, Hovenia, Paliurus, and Rhamnus are cultivated as ornamentals.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Woody vines.
→ 2
2. Tendrils present; fruits schizocarps; ovaries inferior.
Gouania
2. Tendrils absent; fruits drupes; ovaries superior.
→ 3
3. Stems twining, glabrous; leaf blade secondary, and usually tertiary, veins strongly parallel.
Berchemia
3. Stems not twining, hairy; leaf blade secondary veins not strongly parallel, tertiary veins reticulate.
Sageretia
1. Shrubs (sometimes clambering) or trees.
→ 4
4. Sepals usually incurved, sometimes becoming spreading, sepals and petals white, cream, blue, purple, or rarely pink; hypanthium less than 0.5 mm wide.
Ceanothus
4. Sepals spreading or erect, usually yellowish, yellowish green, green, or greenish white to white, sometimes brown, orange or purple; petals white, cream, yellow, yellow-green, or greenish, or 0; hypanthium 1–4 mm wide.
→ 5
5. Leaf blades 3-veined from near base (venation acrodromous).
→ 6
6. Inflorescences compound dichasia, appearing repeatedly dichotomously branched; peduncles and pedicels fleshy in fruit.
Hovenia
6. Inflorescences fascicles, cymes, or thyrses, or flowers solitary; peduncles and pedicels not fleshy in fruit.
→ 7
7. Plants unarmed; fruits capsules.
Colubrina
7. Plants armed with stipular spines; fruits drupes or samaras.
→ 8
8. Fruits samaras; leaf blade secondary veins distal to basal veins well developed; ovary 1/2-inferior; bud scales present.
Paliurus
8. Fruits drupes; leaf blade secondary veins absent or poorly developed distal to basal veins, except sometimes near apex; ovary superior; bud scales absent.
Ziziphus
5. Leaf blades pinnately veined, sometimes basal pair of secondary veins more prominent or blade obscurely veined, appearing 1-veined or vaguely 3-veined from base.
→ 9
9. Leaves alternate, sometimes fascicled or clustered terminally.
→ 10
10. Fruits capsules, sometimes tardily dehiscent; ovaries 1/2-inferior.
Colubrina
10. Fruits drupes; ovaries superior.
→ 11
11. Inflorescences axillary or terminal, spikelike or spicate, paniclelike thyrses, overtopping or extending beyond foliage.
Sageretia
11. Inflorescences axillary, fascicles, umbels, cymes or thyrses, or flowers solitary, within foliage.
→ 12
12. Drupes with 2–4 stones.
→ 13
13. Leaf blade secondary veins arching, not parallel; bud scales present, buds glabrate; flowers usually unisexual, rarely some bisexual (plants polygamous); sepals thin, spreading, not keeled adaxially; petals 0 or 4, not clawed; styles 2–4, connate proximally; hypanthia usually not circumscissile, rarely so at or just proximal to sepal bases; stones longitudinally dehiscent; seeds not beaked, longitudinally furrowed.
Rhamnus
13. Leaf blade secondary veins nearly straight, parallel; bud scales absent, buds hairy; flowers bisexual; sepals fleshy, usually ± erect, sometimes spreading, keeled adaxially; petals (rarely 4–)5, clawed; styles 1; hypanthia usually circumscissile far below sepal bases, rarely not circumscissile; stones indehiscent but open at base; seeds with cartilaginous beak, not furrowed.
Frangula
12. Drupes with 1 stone.
→ 14
14. Leaves not borne on short shoots; plants unarmed; sepals crested adaxially.
Krugiodendron
14. Leaves mostly borne on short shoots, if not, then plants armed with thorns; sepals keeled adaxially.
→ 15
15. Petals 0 (5 in C. ericoides, with linear, revolute leaves); nectaries absent, thin, or margins thickened, lining hypanthium; styles 1.
Condalia
15. Petals 5; nectaries fleshy, filling hypanthium; styles 2(–4).
Ziziphus
9. Leaves opposite or subopposite.
→ 16
16. Plants armed with thorns.
→ 17
17. Leaves early deciduous, usually absent by flowering; fruits capsules.
Adolphia
17. Leaves persistent or deciduous, present at flowering; fruits drupes.
→ 18
18. Inflorescences fascicles or flowers solitary, within foliage; sepals 4, not keeled adaxially; petals 0 or 4; trees or shrubs, erect or spreading.
Rhamnus
18. Inflorescences spikelike or spicate paniclelike thyrses, overtopping or extending beyond foliage; sepals 5, keeled adaxially; petals 5; shrubs arching, sprawling, drooping, or clambering.
Sageretia
16. Plants unarmed.
→ 19
19. Leaves deciduous; petals 4–5.
→ 20
20. Leaf blades not gland-dotted abaxially, secondary veins arching; petals 4; ovules 1 per locule; drupe stones 2–4, dehiscent.
Rhamnus
20. Leaf blades gland-dotted abaxially (secondary veins appearing light- and dark-banded), secondary veins relatively straight; petals 5; ovules 2 per locule; drupe stones 1, indehiscent.
Karwinskia
19. Leaves persistent; petals 0.
→ 21
21. Leaf blade secondary veins arching near margins, higher order veins not forming adaxially raised reticulum; sepals crested adaxially; drupes 5–8 mm.
Krugiodendron
21. Leaf blade secondary veins straight nearly to margins, higher order veins forming adaxially raised reticulum enclosing isodiametric areoles; sepals small-keeled, not crested, adaxially; drupes 10–20 mm.
Reynosia
Source FNA vol. 12, p. 90. FNA vol. 12, p. 43. Author: Guy L. Nesom.
Parent taxa 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
Subordinate taxa
Adolphia, Berchemia, Ceanothus, Colubrina, Condalia, Frangula, Gouania, Hovenia, Karwinskia, Krugiodendron, Paliurus, Reynosia, Rhamnus, Sageretia, Ziziphus
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) Jussieu
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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