Monographs Details: Astragalus flexuosus (Hook.) Douglas ex G.Don var. flexuosus
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
Synonyms:Phaca flexuosa Hook., Tragacantha flexuosa (Hook.) Kuntze, Homalobus flexuosus (Douglas ex Hook.) Rydb., Pisophaca flexuosa (Hook.) Rydb., Astragalus flexuosus var. albus Douglas ex G.Don, Phaca elongata Hook., Astragalus flexuosus var. elongatus (Hook.) M.E.Jones, Pisophaca elongata (Hook.) Rydb., Phaca elongata var. minor Hook., Phaca fendleri A.Gray, Astragalus fendleri (A.Gray) A.Gray, Tragacantha fendleri (A.Gray) Kuntze, Astragalus flexuosus var. fendleri (A.Gray) M.E.Jones, Homalobus fendleri (A.Gray) Rydb., Pisophaca sierrae-blancae Rydb., Astragalus flexuosus var. sierrae-blancae (Rydb.) Barneby, Pisophaca ratonensis Rydb., Pisophaca saundersii Rydb.
Description:Variety Description - Stems 1.5-6 cm. long; herbage greenish or silky-canescent, the vesture appressed, ascending, or rarely incurved; leaflets 11-25 (29), mostly linear or narrowly oblong-oblanceolate; peduncles 4-19 cm. long; racemes (7) 12-26 (30)-flowered, the axis 3-13 cm. long in fruit; calyx 3.5-5.8 long, the tube 2.7 4.3 mm. long, 1.8-2.9 mm. in diameter, the teeth 0.5-1.7 mm. long; banner 7.4—11 mm. long; wings 7.3-10.5 mm. long, the claws 2.6-4.2 mm., the blades 5.3-7.9 mm. long, 1.7-2.7 mm. wide; keel 5.3-7.5 mm. long, the claws 2.3-3.9 mm., the blades 3.4-4.3 mm. long, 1.8-2.4 mm. wide; pod stipitate or subsessile, the stipe 0.5—1.3 mm. long, concealed by the marcescent calyx, the body linear- oblong, -oblanceolate, or narrowly oblong-elliptic in profile, (8) 12-24 mm. long, 2.7-4.8 mm. in diameter, straight, gently incurved, or very rarely a trifle decurved, flattened or very shallowly sulcate dorsally, finely strigulose, villosulous, or rarely glabrous, mottled or not; ovules 14—20.

Distribution and Ecology - Grassy hills and stony knolls on the prairies, open gravelly banks, abandoned sandy fields, cobblestone river bluffs, canyon floors and terraces, in grassland, about oak thickets, in piñon-juniper woodland, ascending (southward) into yellow pine forest, 2200-9300 feet, common and locally abundant in the southern Rocky Mountains from southeastern Wyoming to northcentral New Mexico, in Colorado on both slopes of the Continental Divide but rarer westward, reaching just into southeastern Utah (Abajo Mountains); White and Sacramento Mountains, southcentral New Mexico; Black Hills, South Dakota; again common in the eastern foothills of the Rocky Mountains in Montana and southern Alberta, and thence east, apparently interruptedly, across the plains to southwestern Manitoba, North Dakota, the upper Sioux River in eastern South Dakota, the Minnesota River in westcentral Minnesota, and western Nebraska; southeastern British Columbia (probably introduced, fide J. M. Calder, in litt.).—Map No. 14. May to August, continuing into late September in summer-rainfall areas of New Mexico.


Processes of racial differentiation are clearly at work in var. flexuosus as defined in these pages, but have not reached a point at which segregates can be described in terms of substantial morphological characters. Two relatively distinct phases can be discerned in the material seen from Colorado and New Mexico. One, var. Fendleri sensu Jones (1923, p. 194), is a relatively slender plant with short, pallid-puberulent calyx ± 3.5-4 mm. long and small, pale flowers with banner ± 7.5-9.5 mm. long. The other is more robust in general growth-habit and has a slightly longer, commonly black-hairy calyx and bright purple flowers with banner 9.5-11 mm. long. The first is found at middle altitudes in the mountains, on both slopes of the Divide but more strongly marked westward; the second is most common on the higher prairies and foothills drained by the Arkansas, Canadian, and Pecos Rivers and the Rio Grande. Toward its northern limit var. flexuosus tends to become more densely silky as to calyx and herbage, but is not invariably so; and variation in size of the calyx and corolla and, to a less extent, in color of the calyx-hairs and petals, nearly spans the range exhibited by the two southern forms collectively. It is sometimes possible to predict without help from the label the approximate provenance of a given specimen—a good proof of the existence within the variety of genuine geographic trends; but no practical method of defining the minor variants has been discovered. The six following are the most likely to attract attention:

M. v. 1. Calyx white-silky; petals lilac or pale purple; pod usually elongate, 14—23 mm. long.—Range of the species, except for the s.-w. corner of Colorado and adjoining New Mexico ( = A. flexuosus, sens. strict.).

M. v. 2. Similar, but petals white. An uncommon albinistic mutant (presumably = var. alba Dougl. ex Don).

M. v. 3. Like M. v. 1, but pod gently incurved.—N. Colorado n.-ward ( = Phaca elongata Hook.).

M. v. 4. Robust; leaflets of lower leaves often broadly oblong or obcordate, herbage usually green; calyx 4.2-5 mm. long, black-hairy; petals bright purple, the banner mostly 9.5-11 mm. long; pod 1.3-2.4 cm. long, often mottled.—N.-e. New Mexico and n. to the Arkansas Valley in Colorado ( = Phaca Fendleri Gray; Pisophaca ratonensis Rydb.).

M. v. 5. Similar, but pod glabrous.—White and Sacramento Mountains, New Mexico, where common, but occurring with the pubescent-fruiting form ( = Pisophaca sierrae-blancae).

M. v. 6. Slender; stems and herbage dark green; calyx pale puberulent, 3.5—4 mm. long; petals whitish or pale lilac, the banner 7.5-9.5 mm. long; pod more thinly papery, especially when fully ripe, (8) 12-15 (18) mm. long, thinly puberulent or glabrous.—Rocky Mountains of Colorado, extending into n.-w. New Mexico and s.-e. Utah (= Pisophaca Saundersii, approximately).

Distribution:Wyoming United States of America North America| Colorado United States of America North America| Utah United States of America North America| New Mexico United States of America North America| South Dakota United States of America North America| North Dakota United States of America North America| Nebraska United States of America North America| Minnesota United States of America North America| Montana United States of America North America| British Columbia Canada North America| Alberta Canada North America| Saskatchewan Canada North America| Manitoba Canada North America|