Tall, ordinarily robust and leafy, rarely quite slender, with a thick, woody taproot and knotty root-crown or shortly forking caudex just below soil-level, the stems glabrous, the herbage green but strigulose with fine, straight and nearly straight, appressed or subappressed hairs up to 0.3-0.8 mm. long, the leaflets glabrous or glabrescent above; stems several or numerous, erect and ascending in bushy clumps, 3—10 dm. long, simple or (when stouter) spurred or branched at 1-4 nodes preceding the first peduncle, floriferous from above the middle at about 2-10 distal axils; stipules submembranous, the lowest becoming papery-scarious, pallid, fragile in age, (2) 3-7 mm. long, deltoid-acuminate, triangular, or lanceolate, embracing or decurrent around less than half, or the lowest around ¾ or more of the stem’s circumference; leaves (2) 4-14 cm. long, shortly petioled or the upper ones subsessile, with 13—25 (27) elliptic, narrowly oblong, lanceolate, or oblanceolate, flat, dorsally keeled leaflets (3) 5-23 mm. long, those of the lower leaves commonly obtuse, or subobtuse and mucronulate (exceptionally emarginate), those of the upper leaves fewer, smaller, and often acute or subacute; peduncles incurved-ascending, 5-15 cm. long, little or greatly surpassing the leaf; racemes loosely, sometimes interruptedly or even remotely 20-95-flowered, the flowers early deflexed, the axis much elongating, 8-30 cm. long in fruit; bracts membranous, linear-lanceolate, 1.2-3 mm. long; pedicels early arched outward and in age downward, at anthesis 0.6-1 mm., in fruit a little thickened, 1.2-3 mm. long; bracteoles 0; calyx 3.5-4.4 mm. long, strigulose with white hairs, the subsymmetric disc 0.5-0.8 mm. deep, the campanulate tube 1.8-2.2 mm. long, 1.6-2 mm. in diameter, the slenderly subulate, incurved teeth 1.4-2.2 mm. long, the dorsal one usually longest, the whole becoming papery, ruptured, marcescent; petals whitish, immaculate, more or less marcescent and ochroleucous when faded; banner abruptly recurved through 45°, further in withering, ovate-elliptic or -cuneate, shallowly notched, 4.8-6 mm. long, 3.2-4.4 mm. wide; wings (0.2-1.4 mm. longer than the banner) 5.2-7 mm. long, the claws 1.5-2 mm., the obliquely elliptic, lance-elliptic, or obliquely obovate, obtuse, rather strongly incurved blades 4.1-5.5 mm. long, 1.6-2 mm. wide; keel 3.8-4.6 mm. long, the claws 1.6-2 mm., the nearly half-circular blades 2.4—2.9 mm. long, 1.4-1.8 mm. wide, incurved through 100-115° to the bluntly or more often sharply deltoid, slightly porrect apex; anthers 0.3-0.4 (0.45) mm. long; pod deflexed, sessile, lunately half-ovoid or lance-ovoid, slightly incurved, 4.5-7 mm. long, 1.3-2.3 mm. in diameter, rounded or cuneate at base, shortly cuspidate at apex, triquetrously compressed, carinate ventrally by the promient suture, sulcate dorsally, the lateral angles obtuse, the green, glabrous valves becoming stramineous, stiffly papery, finely cross-reticulate, inflexed as a complete or subcomplete septum 0.6—1 mm. wide; ovules (2) 4-6; seeds narrowly oblong, brown, sometimes purple-dotted, smooth and sublustrous, 2.7-3 mm. long.—Collections: 16 (ii); representative: Abrams 6269 (NY, US); M. S. Baker 10,852 (CAS); Ripley & Barneby 6909 (CAS, NY, RSA); G. S. Lyon 1912 (CAS).
Sandy stream banks, gravel bars moist in spring, hillside seeps and marshy pockets on open slopes, apparently confined to serpentine, local and rather rare, in two widely separated areas in the inner Coast Ranges of California: between 650 and 3000 feet, in the mountains of northern Napa and southeastern Lake Counties (Mt. Saint Helena and Aetna Springs to Knoxville, north to Mt. Hannah and Mt. Cobb, and up to 5000 feet on Snow Mt.); and at about 4450 feet near the head of San Benito River in the San Carlos Range, San Benito County.—Map No. 155.—June to September.
Astragalus Clevelandi (Daniel Cleveland, 1838-1929) Greene in Bull. Torr. Club 9: 121 1882.—"Collected in Indian Valley, Lake County, Cal., June, 1882, by Mr. D. Cleveland."—Holotypus, ND! isotypi, GH, SD!—Hamosa Clevelandi (Greene) Rydb. in op. cit. 54: 334. 1927.
The Cleveland milk-vetch, the only astragalus of its type in California, is recognized at a glance by the long, open racemes of tiny, reflexed, whitish flowers which are followed by small, shining green pods containing only two or three seeds in either chamber. By comparison with the Mexican Micranthi it is a coarse leafy plant; vigorous individuals reach a stature of three or even four feet, including the projecting flower-spikes, in favorable places. The species most nearly resembling it in technical characters is A. Goldmani, distant nearly a thousand miles southward in Chihuahua, but the relationship is probably not really close. A noteworthy feature of A. Clevelandi is its bicentric range, evidence of its relic nature. Presumably the Cleveland milk-vetch formed part of a floristic invasion directed northward from the Mexican plateau, perhaps during one of the warm interglacial periods. Preconditioned to a summer period of bloom, the species has become adapted in the absence of summer rains to a mesophytic habitat. Probably it is only on serpentine, which inhibits the rank vegetation ordinarily found along streams in temperate climes, that an astragalus could find or maintain a foothold in soils even seasonally moist. If this view is correct, the role of serpentine bedrock is here a negative one, and the highly mineralized soils derived from it are not required for successful growth.