notes This robust and riotously floriferous specimen of Astragalus pachypus var. pachypus was spotted by the illustrious plant-explorer and naturalist RT Hawke....while he was simultaneously driving at 60+ mph ;-). A handsome movie star was wrangled from nearby to provide a sense of scale. The images here provide all that's needed to get to species using the Astragalus key in the Jepson eFlora, given the hints that: 1) this plant is not an annual; 2) my thumbnail is 15 mm long (see 3rd image); and 3) miraculously, one fruit was present (and captured near the middle of the left edge the 5th photo of the series). The crucial characters in the keying sequence here, using the Jepson key, are: plants of the Mojave Desert (Group 2); terminal leaflet jointed to midrib, like other leaflets (see 8th image); hairs simple (i.e. not dolabriform); perennial; fruit glabrous; leaflet hairs present on both sides (here densely silvery-strigulose adaxially, less densely so abaxially); flowers large, keel 15-17 mm; calyx strigose, fruit not ''bladdery''; flowers white, leaflets narrow and very well-spaced along rachis; banner around 20 mm.
Somewhat puzzling to me is the key's reference to the ''banner recurved < 50°''. If they mean the (distal) banner (blade) is recurved (upwards?) from the apex of the keel by < 50° I can buy that...as in this plant the apices of the keels are upturned by about 40° from the horizontal axis of the calyx-tube and petal bases. That is, the distal portion (or ''blade'') of the banners are roughly perpendicular to the horizontal axis of the calyces & basal portions (or ''claws'') of the petals...which I think would be better described for my photos as ''banners 70-90+° recurved'' (e.g. see 3rd photo). But perhaps the flowers here are at variance with those typical for the species?
I like to consult Barnaby's epic ''Atlas of North American Astragalus'' when working on an Astragalus ID (link here...but note the 'book-reading interface' is a bit unwieldy). To get to A. pachypus in Barnaby's ''Key to Mohave (sic) and Colorado Deserts'' (on pg. 82) one needs to know that...in addition to what's visible in the photos here...the stipules of the lower leaves are not fused, and the fruits have a short stipe at their bases (e.g. as seen here). Barnaby's description & discussion of A. pachypus var. pachypus (on pp. 487-489) is in excellent agreement with the plant here...except he describes typical plants as ''sparsely leafy'', which is not the case for this remarkably robust plant. Like the Jepson treatment, he similarly states the banner is ''recurved through about 45° ''...though he also notes the keel is 'rather gently incurved through 50-95° '! Note that Barnaby specifies in his introduction (on pg. 14) that he measures the banner angle as swept (presumably downward?) ''from the vertical''. The conventions & usage of the ''banner angle character'' are thus rather confusing to me (I would think the natural inclination would be to measure the angle ''upwards'' between the axis of calyx tube and petal bases to the plane of the banner...all as seen laterally in a vertical cross-section).
Barnaby mentions a record for the species at 'Ricardo, Kern Co.'...which is an old name for the locality where the State Park Headquarters & campground are now. There are a number of CalFlora records for A. pachypus var. pachypus near here...and this useful plant list for Red Rock State Park lists only 3 species of Astragalus...of which only A. pachypus var. pachypus fits here.
At any rate, this is a beautiful Astragalus species, and a lovely exemplar. Thanks, RT! :-)
