3. Competition: Due to its spreading by rhizomes the species 

 seems competetively well-adapted to survive in the dense grass 

 and shrub cover at the site. It doesn't, however, extend into 

 nearby dense Agropyron smithii grassland. 



4. Herbivory: The ca 50 percent decrease in the population 

 from early July to late August was probably because the area 

 went from moderately to heavily grazed within this time, and 

 a few individuals had been cropped. It is likely that most 

 plants were mechanically damaged rather than grazed because 

 the latex in this genus is unpalatable to most animals. 



F. Assessment and management recommendations: This species is 

 detrimentally affected by late season grazing. Exclusion from 

 grazing or a shift in the period of grazing to earlier in the 

 season would diminish the threats. Revisits to determine seed set 

 are appropriate to include in assessing its management response. 

 This species was not found in the South Dakota units, is a 

 peripheral species addition to the Montana flora, is affected by 

 management actions, and is recommended for designation as 

 sensitive. 



Asclepias stenophylla Gray 

 Asclepiadaceae 

 Narrow-leaved milkweed 

 A. Description 



1. General description: Herbaceous perennial, stems mostly 

 single or sometimes paired from a stout rootstock, prostrate, 

 decumbent or upright; usually simple, 25-51(91) cm (10-20 in), 

 puberulent to glabrate. Stamens evolved into a column to 

 which are attached sac-like "hoods", each hood with an 

 incurved "horn" appendage. Early flowering was in progress on 

 12 June 1994, and continued through 2 July in the study area. 

 Plants could not be relocated on 28 August. 



2. Technical description: Perennial herb from a stout 

 vertical rootstock; stems solitary or occasionally paired, 

 upright or decumbent from a mostly simple, thickened base, 

 simple or occasionally sparingly branched, slender, 2-10 dm 

 tall, puberulent to glabrate. Leaves mostly alternate to 

 subopposite; blades linear, erect to moderately spreading, 

 puberulent, apex narrowly acute, margins often revolute, base 

 narrowly acute, petiole, if present, 1-2 mm long. 

 Inf loresences few to several, scattered in leaf axils of upper 

 1/3 - 2/3 of plant, 10- to 25-flowered; peduncles 1-4(15) mm 

 long or more commonly none; pedicels slender, 0.5-1.1 cm long, 

 puberulent. Flowers 7.5-9 mm tall, 1.1-1.2 mm wide; hoods 

 narrowly oblong, attached in lower 1/4, erect, 3.3-3.8 mm 

 long, somewhat fleshy, freely open above, the apex deeply 

 emarginate and appearing 3-toothed or lobed, the shorter 



20 



