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Astragalus gruinus is endemic to the Sierra San Pedro Martir of Baja California and was seen often during our two-day workshop growing in sandy areas (i.e. grus) of forest openings. It seemed to be the most common among the 8 Astragalus taxa appearing on the workshop plant list for the national park area. The other seven taxa were: acutirostris, circumdatus, didymocarpus obispoensis, douglasii glaberrimus, douglasii parishii, palmeri, and prorifer. During our two day visit, we only encountered one other species, A. circumdatus...and only once that I can recall.

I was able to confirm most the characters in the keying sequence for A. gruinus in Wiggins (1980) from the photos posted here. Among these are:

Pods bladdery-inflated, sessile in the calyx, 1-loculed (i.e. lacking a complete inner septum), beak 4-5mm; stipules all free opposite the petiole bases (not connate); racemes 10+ flowered; plants green (not silvery); terminal leaflet jointed to rachis; inflorescence not crowded into heads; peduncles 5-9 cm; plants not of alkali habitat; herbage and pods strigose to glabrate; pods 1.8-3cm, spreading (not ascending); petals purple; leaflets 17-25; Jun-Sep.

More images of Astragalus gruinus can be found on the SDMNH photo page (search under the species name there).

For those who absolutely love astragalean scholarship, Barneby's original description of A. gruinus appears on pp. 846–849 of the Memoirs of The New York Botanical Garden, Vol. 13 (1964)...and it can be read online starting at the bottom of pg. 846 at this link. His treatments are amazingly detailed!

BTW, Barneby used the common name ''crane milk-vetch'' for A. gruinus, since as he explained...the Spanish word for crane is grulla, or grui in Latin...and thus gruinus means ''of the crane''. Looking at the images, I can imagine how the arching leaves and inflorescence branches could give the impression of group of cranes foraging in shallow water :-) However, ''La Grulla'' is also a place name within the center of distribution for A. gruinus. Barneby indicated (in 1964) that the known occurrences of A. gruinus were limited to the Sierra San Pedro Martir, and apparently that continues to be the case, as the 2010 annotated plant list by Thorne, Moran & Minnich states that A. gruinus is endemic to the Sierra San Pedro Martir.