Monographs Details: Astragalus didymocarpus subsp. milesianus (Rydb.) Hoover
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:

360b.  Astragalus didymocarpus var. Milesianus

Closely resembling var. didymocarpus except for the larger flowers, the racemes at full anthesis (10) 12—15 mm. in diameter; stems mostly erect, coarse or sometimes quite slender; leaflets (9) 11-15; calyx at anthesis (3.5) 4-5.7 mm. long, the tube (2.5) 3—3.8 mm. long, 1.8—2.4 mm. in diameter, the teeth 1-2.4 mm. long, the ventral pair broadest and often longest; banner oblanceolate, 7.5-10 mm. long, 3.4-4 mm. wide; wings 5.8-8 mm. long, the claws (2.5) 3.3-4.1 mm., the blades 4.2—5 mm. long, 1.3—1.8 mm. wide; keel (4.7) 5.3—6.9 mm. long, the claws (2.6) 3—3.7 mm., the blades 2.5-3.6 mm. long, 1.5-1.8 mm. wide, incurved through ± 110° to the broadly rounded apex; anthers (0.25) 0.3-0.4 mm. long; pod ± 3.5-4 mm. long, glabrous or distally pilosulous.—Collections: 10 (o); representative: J. H. Barber (from Morro) in 1899 (UC); Belshaw 1740 (UC); Elmer 3838 (CAS, NY, ORE, UC).

Grassy hillsides and meadows along and near the ocean, mostly below 200 feet, apparently quite local, known only from southern San Luis Obispo and western Santa Barbara Counties, California.—Map No. 160.—March to May.

Astragalus didymocarpus var. Milesianus (Rydb.) Jeps., Fl. Calif. 2: 376. 1936, based on Hesperastragalus Milesianus (the collector) Rydb. in Bull. Torr. Club 53: 169. 1926.—"Type collected at San Luis Obispo, California, April 1886, M. M. Miles.’’—Holotypus, NY!

The var. Milesianus apparently replaces var. didymocarpus in the coastal region from Gaviota and Lompoc north to Cayucos. Its extreme phase is found only around San Luis Obispo and Morro, where the plants are immediately distinguished from var. didymocarpus by their thick spikes of comparatively handsome and brightly colored flowers. The variety was recognized independently by Rydberg and Jepson, who annotated the Barber specimen cited (UC) with an unpublished name. The material from Santa Barbara County is less well marked but has flowers substantially larger than coastal and insular var. didymocarpus from farther south.

The variety was collected first in 1832, between San Miguel and Santa Barbara, by Thomas Coulter (No. 440, K).