5. CEANOTHUS L.
Small trees or shrubs, with slender terete branches, without a terminal bud, and small scaly axillary buds. Leaves petiolate, 3-ribbed from the base, or pinnately veined, persistent in the arborescent species. Flowers on colored pedicels, in umbellate fascicles collected in dense or prolonged terminal or axillary thyrsoid cymes or panicles, blue or white; calyx colored, with a turbinate or hemispheric tube and 5 triangular membranaceous petaloid lobes; disk fleshy, thickened above; petals 5, inserted under the margin of the disk, unguiculate, wide-spreading, deciduous, the long claw infolded round the stamens; stamens 5, inserted with and opposite the petals, persistent, filaments spreading; ovary partly immersed in and more or less adnate to the disk, 3-celled, sometimes 3-angled, the angles often surmounted by a fleshy gland persistent on the fruit; styles short, united below; stigmas 3-lobed with spreading lobes; ovule erect from the base of the cell. Fruit 3-lobed, subglobose, with a thin outer coat, soon becoming dry, and separating into 3 crustaceous or cartilaginous longitudinally 2-valved nutlets. Seeds erect, obovoid, lenticellate, with a broad basal excrescence surrounding the hilum; seed-coat thin, crustaceous; albumen fleshy; embryo axile; cotyledons oval or obovate.
Ceanothus is confined to the temperate and warmer regions of North America, with about thirty species, mostly belonging to California. The leaves, bark, and roots are astringent and tonic. Of the species of the United States three are small trees.
The generic name is from κεάνωθος, the classical name of some spiny plant.
CONSPECTUS OF THE ARBORESCENT SPECIES OF THE UNITED STATES.
Branchlets not spinose, leaves 3-ribbed. Leaves broad-ovate to elliptic, subcordate or rounded at base, pale and tomentose below.1. [C. arboreus] (G). Leaves elliptic, acute at base, glabrous except on the veins below.2. [C. thyrsiflorus] (G). Branchlets spinose; leaves with a single midrib, mostly elliptic, rounded or subcordate at base, glabrous.3. [C. spinosus] (G).
1. [Ceanothus arboreus] Greene.
Leaves broad-ovate or elliptic, acute, conspicuously glandular-crenate, dark green and softly puberulent on the upper surface, pale and densely tomentose on the lower surface, 2½′—4′ long and 1′—2½′ wide, with prominent veins; petioles stout, pubescent, ½′—1′ in length; stipules subulate from a broad triangular base, ¼′ long. Flowers pale blue opening in July and August, on slender hairy pedicels ½′—1′ long, from the axils of large scarious caducous bracts, in ample compound densely hoary-pubescent thyrsoid clusters 3′—4′ long and 1½′—2′ wide, on a leafy or naked axillary peduncle at the end of young branches. Fruit black, ¼′ across.
A round-headed tree, 20°—25° high, with a straight trunk 6′—10′ in diameter, dividing 4°—5° from the ground into many stout spreading branches, and slender slightly angled pale brown branchlets covered with short dense tomentum, becoming in their second season terete, nearly glabrous, roughened with scattered lenticels and marked by large elevated leaf-scars; often a shrub. Bark of the trunk dark brown, about ⅛′ thick, and broken into small square plates separating into thick scales.
Distribution. Santa Catalina, Santa Cruz, and Santa Rosa Islands of the Santa Barbara group off the coast of southern California; most abundant and of its largest size on the northern slopes of Santa Cruz; on the other islands usually shrubby, with numerous slender stems.
2. [Ceanothus thyrsiflorus] Eschs. Blue Myrtle. California Lilac.
Leaves oblong or oblong-ovate, minutely glandular-serrate, smooth and lustrous on the upper surface and paler and slightly pubescent on the lower surface, especially along the 3 prominent ribs, 1′—1½′ long and ½′—1′ wide; petioles stout, ⅓′—½′ in length; stipules membranaceous, acute. Flowers blue or white, appearing in early spring in small pedunculate corymbs from the axils of minute deciduous bracts, and collected into slender rather loose thyrsoid clusters 2′—3′ long in the axils of upper leaves or of small scarious bracts, and usually surmounted by the terminal leafy shoot of the branch. Fruit ripening from July to December, black; seeds 1/12′ long, smooth, dark brown or nearly black.
A tree, occasionally 35° high, with a trunk 12′—14′ in diameter, dividing 5°—6° from the ground into many small wide-spreading branches, and conspicuously angled pale yellow-green branchlets slightly pubescent when they first appear, soon becoming glabrous; more often a tall or low shrub. Bark of the trunk thin, with a bright red-brown surface separating into thin narrow appressed scales. Wood close-grained, rather soft, light brown, with thin darker colored sapwood.
Distribution. Shady hillsides on the borders of the forest and often in the neighborhood of streams; coast mountains of California from Mendocino County to the valley of the San Luis Rey River, San Diego County; of its largest size northward, and in the Redwood-forests of the Santa Cruz Mountains; southward often a low shrub, frequently flowering on the wind-swept shores of the ocean when only 1°—2° high.
3. [Ceanothus spinosus] Nutt. Lilac.
Leaves elliptic to oblong, full and rounded, apiculate or often slightly emarginate or gradually narrowed and pointed or rarely 3-lobed at apex, and rounded or cuneate at base, when they unfold villose-pubescent below along the stout midrib and obscure primary veins, soon glabrous, coriaceous, usually about 1′ long and ½′ wide; petioles stout, ⅙′—⅓′ in length, at first villose, becoming nearly glabrous; leaves on vigorous shoots sometimes ovate, conspicuously 3-nerved, irregularly serrate with incurved apiculate teeth, or coarsely dentate, and often 1½′ long and ⅝′ wide; stipules minute, acute. Flowers light or dark blue, very fragrant, opening from March until May, in lax corymbs from the axils of acute pubescent red caducous bracts on upper leafy branchlets of the year, the whole inflorescence forming an open thyrsus often 5′—6′ long and 3′—4′ thick, leafless toward the apex. Fruit depressed, obscurely lobed, crestless, black, ¼′—⅓′ in diameter.
A tree, 18°—20° high, with a trunk 5′—6′ in diameter, upright branches forming a narrow open head, and slender divaricate angled branchlets pubescent or puberulous when they first appear, soon glabrous, bright green, ultimately reddish brown, frequently terminating in sharp leafless thorn-like points; more often shrubby. Bark of the trunk thin, red-brown, roughened by small closely appressed scales.
Distribution. California, common in mountain cañons near the coast of Santa Barbara, Ventura, and Los Angeles Counties; often forming a dense undergrowth in the forest, which it enlivens for many weeks in early spring by its large clusters of bright blue flowers.