Astragalus nuttallii (Torr. & A.Gray) J.T.Howell

Authors

Rupert C. Barneby

Authority

Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.

Family

Fabaceae

Scientific Name

Astragalus nuttallii (Torr. & A.Gray) J.T.Howell

Type

"Borders of woods near the sea, St. Barbara, California... Nuttall."—Holotypus, labeled by Nuttall "Phaca *inflata. U. California.," with Torrey’s annotation: "non Gillies. P. Nuttallii T. & G.," NY (herb. Torr.)! isotypus, BM!

Description

Species Description - Commonly robust and amply leafy, densely to quite thinly villous-villosulous with fine, spreading, incurved-ascending, or curly hairs up to 0.5-1.25 (1.4) mm. long, the herbage softly canescent, cinereous, or green, the leaflets equally pubescent on both sides, or thinly so above, or the vesture reduced to a few cilia on the leaflet-margins and a line of hairs on the midrib beneath; stems several or numerous, 2-10 dm. long, most commonly diffuse and ascending, in exposed sites becoming prostrate and matted, when sheltered sometimes erect or assurgent, fistular when most robust, commonly glabrous and purplish at base, branched or spurred at 1-6 nodes preceding the first peduncle, floriferous upward from about 3—10 axils, the whole plant forming dense mats, low bushy, or mounded, or sometimes erect and bushy clumps; stipules membranous becoming papery-scarious, pallid or stramineous and sublustrous, commonly glabrous dorsally but sometimes thinly pubescent distally and nearly always ciliate, variable in size and attachment, 3-14 mm. long; leaves usually arcuately spreading, (2.5) 4-17 cm. long, shortly petioled or the uppermost subsessile, with (21) 23-43 crowded or moderately distant, obovate, obovate-cuneate, oblong-obovate, narrowly to broadly oblong, or oblanceolate, retuse, emarginate, obtuse, or obtuse and mucronulate, penninerved, dorsally keeled, flat or loosely folded leaflets (2) 3.5—25 (28) mm. long; peduncles erect or incurved-ascending, at least the lowest ones usually stout, 6-15 (18) cm. long, commonly longer than or equaling, rarely shorter than the leaf; racemes densely (15) 20-90 (125)-flowered, the flowers early nodding, the axis elongating, mostly 3-19 cm. in fruit (only some subterminal or unseasonable ones shorter or fewer-flowered); bracts membranous, narrowly triangular, lanceolate, or rarely ovate, 1.5-4 (5) mm. long; pedicels at anthesis slender, ascending or arched outward, 0.8-2.5 mm. long, in fruit thickened, mostly straight and ascending, (2.5) 3-5.5 (7) mm. long; bracteoles 0-2, minute or quite conspicuous when present; calyx (5.5) 5.8-8.2 (9) mm. long, thinly to densely villosulous or loosely strigulose with white, fuscous, or mixed hairs, the oblique disc 0.9-1.5 mm. deep, the campanulate or somewhat ovoid-campanulate, more or less tumid, membranous and pallid tube asymmetric or dorsally gibbous at base, (4) 4.3-5.7 (6) mm. long, (2.6) 3.1-4.8 mm. in diameter, the broadly subulate or triangular teeth (1.1) 1.3-3.1 mm. long, the whole becoming papery, ruptured, marcescent; petals greenish-white or cream-colored, the keel and sometimes the wings and banner tipped or suffused with pinkish-lilac; banner poorly developed relative to the wings, rhombic-spatulate or spatulate-oblanceolate, (10) 11-15 mm. long, the long-cuneate claw expanded into a short, suborbicular- flabellate, shallowly notched or emarginate blade (5.8) 6.2-9.2 mm. wide, the whole recurved through about 40°, the distal margins folded back all around; wings 1.1 mm. shorter to 1.4 mm. longer than the banner, (9.7) 10.5-16.5 mm. long, the claws (5.5) 6.3-9 mm., the narrowly oblong, oblong-oblanceolate, or -elliptic, obtuse, truncate, or shallowly notched, straight or gently incurved blades (5.3) 5.8-7.9 mm. long, (1.7) 2-3.2 mm. wide; keel (9.7) 10.5-14 mm. long, the claws (5.6) 5.8-7.1 mm., the half-obovate, obliquely obovate, or triangular blades (4.5) 4.7-6.5 mm. long, (2.2) 2.5-3.6 mm. wide, abruptly incurved through 90-100° to the broad, blunt, rarely sharply deltoid, sometimes obscurely porrect apex; anthers (0.5) 0.55-0.8 mm. long; pod loosely spreading, ascending, or the lowest ones on a raceme declined, sessile, very obliquely (rarely subsym- metrically) ovoid, ovoid-ellipsoid, or half-ovoid, -obovoid, or -ovoid-ellipsoid, bladdery-inflated, (2) 2.5-5.5 (6) cm. long, 1.5-2.7 cm. in diameter, rounded or broadly obconic at base, contracted distally into a short, broadly deltoid, or longer, triangular-acuminate, erect or slightly incurved, laterally compressed beak, openly or sometimes deeply sulcate ventrally and sometimes also shallowly so dorsally, the thin, pale green or minutely purple-dotted, glabrous or thinly villosulous valves becoming papery, stramineous (often brown or purple-cheeked), lustrous, delicately cross-reticulate, not inflexed, the funicular flange narrow or subobsolete, (0.2) 0.4-1 mm. long; seeds brown or purplish-brown, smooth but dull, 2.2—3.8 mm. long.

Discussion

The Nuttall milk-vetch, a rather coarse but nevertheless handsome species notable for the great size attained by the bladdery fruits, is the one perennial astragalus common along the immediate coast of California between Point Conception and Cape Mendocino. A robust, usually erect form is found a little inland on San Francisco peninsula, but it is otherwise a strictly maritime plant. Difficulty in naming this milk-vetch correctly is likely to arise only in San Luis Obispo and western Santa Barbara Counties, where the related A. curtipes comes out on rock outcrops and roadcuts to within a few hundred yards of the ocean and where A. pomonensis is found occasionally in sandy fields within sound of the Pacific surf. The key to the subsection should serve to distinguish these easily enough.

The species is rather uniform in its reproductive parts, but extremely polymorphic in superficial matters of vesture and growth-habit. An analysis of the variation, the results of which are incorporated in the following key, has been published elsewhere (Barneby, 1958, pp. 133-4).