29 



that become more remote as the plant matures. Yellowish-white flowers are ca. 20 mm long with a 

 reflexed upper petal and a blackish-hairy calyx, 8-10 mm long. Glabrous, green to reddish, oblong pods 

 are 15-20 mm long and 2-chambered in cross-section. Each pod is on a stem as long as the pod that 

 spreads out and then arches up, holding the fruit nearly erect (Figure 12; Appendix D-4). Astragalus 

 scaphoides flowers in mid-late June and produces fruit from June-July. 



The long fruit stalks arch out and up, holding the pods like a candelabra. The pods are also 4-6 mm 

 wide, collectively distinguishing it from the similar species, A. atropubescens and A. terminalis. 



GEOGRAPHICAL DISTRIBUTION 



Global distribution: Astragalus scaphoides is a narrow endemic restricted to Lemhi County, 

 Idaho, where it is in the foothills of the Bitterroot Mountains and adjoining valleys, and in a 

 separate area of the foothills and high plains in southwestern Beaverhead County, Montana. 



Montana distribution: Astragalus scaphoides is found in southwestern Beaverhead County in 

 the drainages of the Grasshopper, Horse Prairie, and Medicine Lodge Creeks, and in the upper 

 Beaverhead River, constituting a total of 17 Montana occurrences. The majority, including all of 

 the largest occurrences, are on BLM lands (Figure 13). 



Grasshopper distribution: Twelve of the 17 Montana occurrences are from the Grasshopper 

 Study Area (Figure 13). One is an historic collection made on private land at the mouth of 

 Grasshopper Creek that is presumed extirpated, and one is an historic collection made near the 

 Bannack townsite that has also likely been destroyed. 



HABITAT: Astragalus scaphoides is distributed across "open valleys, low hills, (and) canyon benches 

 ..." (Bameby 1964) in foothills and lower montane settings. In the study area, it occurs on lower slopes, 

 terraces, and flood plains, extending high on slopes when the slopes are gentle or sheltered. It occupies a 

 wide range of slopes and aspects. Mesic microhabitat appears to be good potential habitat throughout 

 the study area, though large areas of potential habitat have been altered and are unoccupied such as the 

 valleybottoms of Grasshopper Creek and tributary mouths (see management discussion). With higher 

 elevations, as found outside the study area in the Tendoy Mountains, the species extends onto exposed, 

 southerly slopes. Its elevation in Montana ranges from 5300-6900 ft. 



It typically grows in sagebrush grasslands dominated by Artemisia tridentata and Agropyron spicatum. 

 Under heavy grazing, the sage takes on a rank, spindly form and Astragalus scaphoides is absent or 

 present in only trace amounts (e.g., segments of Cold Springs Creek, Appendix D-6), with or without, 

 population remnants at the base of the valley slope (Appendix D-15). Other shrub species which are 

 subdominant or in some cases replace big sagebrush in these habitats include Artemisia nova and 

 Chrysothamnus nauseosus. Common or subdominant grasses at the sites include Stipa comata, 

 Oryzopsis hymenoides, Festuca idahoensis, and Poa secunda. Although there are several other species 

 of milkvetches in the vicinity, mc\\xd\ng Astragalus agrostis, A. adsurgens. A. atropubescens, A. 

 drummondii, and A. lentiginosus, they are not regularly found in the same mesic setting as A. 

 scaphoides. 



