Monographs Details: Astragalus tener A.Gray var. tener
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
Discussion:

327a. Astragalus tener var. tener

Stems 1-several, (4) 6—30 (35) cm. long; leaves (2) 3—9 cm. long, with 7-17 leaflets variable in outline as described for the species; racemes (3) 5-10 (12)-flowered; calyx 3.5-5.4 mm. long, the disc 0.5-0.9 mm. deep, the tube 1.9-3.2 mm. long, 1.7-2.4 mm. in diameter, the teeth 1.3-2.3 mm. long; banner 4.4-6.4 mm. wide; wings 7.3-9 (9.5) mm. long, the claws 2.1-3.1 mm., the blades 5.7-7 (7.4) mm. long, 2-2.8 mm. wide; keel-claws 2.1-3.2 mm. long, the blades 3.3-4.2 mm. long, 1.9-2.2 mm. wide; pod 1-1.6 (2) cm. long, 1.8-3.5 mm. in diameter.—Collections: 22 (o); representative: Eastwood & Howell 5266 (CAS, GH, NY); Eastwood 3818 (CAS, GH, NY, WS); Hoover 393 (NY, UC), 4332 (NY); E. K. Abbott (from near Salinas) in 1889 (CAS).

Alkaline flats and low meadows moist in spring, below 200 feet, local but forming colonies, central Great Valley and Delta region of California, from Solano to Stanislaus County, west to the east shore of San Francisco Bay (where now largely exterminated) and (formerly) to the east slope of San Francisco Peninsula; apparently isolated in the lower valleys of the San Benito and Salinas Rivers in Monterey and San Benito Counties.—Map No. 148.—March to early June.

Astragalus tener (tender and delicate) Gray in Proc. Amer. Acad. 6: 206. 1864.— "California, Douglas: from Monterey or San Francisco."—Holotypus, GH! isotypi, BM, NY, OXF, P!—Tragacantha tenera (Gray) O. Kze., Rev. Gen. 948. 1891. Hamosa tenera (Gray) Rydb. in Bull. Torr. Club 54: 323. 1927.

Phaca astragalina ß H. & A., Bot. Beechey Voy. 334. 1838.—" ... California ...," no collector mentioned, but by inference Douglas.—Holotypus, so labeled, K!

Astragalus Hypoglottis var. strigosus (stiffly hairy) Kell, in Proc. Calif. Acad. Sci. 2: 115, fig. 37. 1861.—No locality or collector mentioned.—No spm. preserved at CAS, probably none extant.—A. strigosus (Kell.) Sheld. in Minn. Bot Stud. 1: 24. 1894 (non A. strigosus Coult. & Fish., 1893). Hamosa Kelloggiana (Albert Kellogg, 1813-1887, a founder of CAS) Rydb. in Bull. Torr. Club 54: 323. 1927.

Astragalus tener var. rattanoides (resembling A. Rattani) Jones, Rev. Astrag. 268, Pl. 68. 1923 ("Rattanoides").—"Mt. Eden, California, Brandegee, April 27, 1890."—Holotypus, UC! isotypi, DS, NY, US!—Hamosa rattanoides (Jones) Rydb. in Bull. Torr. Club 54 : 324. 1927.

The alkali milk-vetch, A. tener, is the prototype of the cismontane annual astragali with narrow, dorsally grooved pods. It may be distinguished from its close kindred by the sub- capitate most fugitive annuals of dry climates the plants vary greatly in stature from year to year, and from one to the next within a colony. The leaflets of var. tener are subject to an unusual type of variation, first noticed by Dr. Kellogg (1861, l.c.) and described in detail by Jepson (1936, p. 378) from observations at Vacaville in Solano County. Within the space of a few square feet the leaflets sometimes vary from linear and acute to oblong-obcordate; they may be alike in all leaves of some plants or pass upward from oblong in the lower to linear and either obtuse or acute in the upper leaves. The pod of the alkali milk-vetch may be straight, gently incurved, or rarely a trifle decurved, and varies in orientation from ascending to declined. This is probably correlated with the attitude of the peduncle, which is apparently sometimes divaricate and possibly humistrate when the fruits are ripe. The valves of the pod may be either glabrous or strigulose, both states being found occasionally together. Thus Hamosa Kelloggiana, with lunately incurved, glabrous pod and linear leaflets in the upper leaves, and H. rattanoides, which differs in its pubescent pod from the preceding and from the typus of A. tener in its narrower leaflets, are clearly no more than arbitrarily selected individual variations belonging to a continuous series.

A plant of adobe flats and low-lying meadows in the central Great Valley and around San Francisco Bay, where man has so vastly altered the pristine ecology and destroyed forever hundreds of square miles of the original plant cover, A. tener is a comparatively rare plant, no longer to be found in most of the stations marked on the distribution map. Unless unpublished notes of David Douglas exist, its type-locality cannot be known with certainty. However Howell (in Leafl. West. Bot. 2: 140. 1938) found an especially close match for an isotypus (LE) in the specimen collected near Salinas by Dr. Abbott (CAS, cited supra), and it is possible that Douglas first encountered the alkali milk-vetch in the lower Salinas Valley.