Senecio debilis Nutt. 

 Rocky Mountain ragwort 



A. DESCRIPTION 



1. General description: This herbaceous perennial belongs to a 

 large genus in the Asteraceae (sunflower family) . The plants 

 have a basal rosette of simple petioled leaves. Leaves along 

 the flowering stem are progressively smaller toward the top, 

 more deeply pinnately lobed and without petioles. The flower 

 heads have a single series of green bracts of equal length. 

 The yellow to orange flowers are all tubular and have pappuses 

 of capillary bristles. 



2. Diagnostic characters: S. debilis can be separated from 

 other Montana species of Senecio by its lack of ray flowers 

 and its stem leaves wtih deep, rounded lobes (Dorn 1984). 



B. GEOGRAPHIC DISTRIBUTION 



1. Species range: "...central Idaho and southwest Montana to 

 Colorado (Hitchcock and Cronquist 1973)." 



2. Montana distribution: Previously known from twelve sites 

 in Beaverhead, Lewis and Clark, and Madison counties. 



3. Occurrences in the study area: Six populations were 

 documented in the basins of Muddy Creek and upper Big Sheep 

 Creek. 



C. HABITAT 



Populations in the study area occur at elevations from 6,800 

 to 7,200 ft. in moist alkaline meadows dominated by Potentilla 

 fruticosa, Juncus balticus, Deschampsia caespitosa and Carex 

 praegracilis . Most of the sites are subject to use by 

 livestock, some are heavily grazed. 



D. POPULATION BIOLOGY 



Populations in the study area are relatively large with 

 estimated numbers ranging from over 100 to 5,000 plants. 



E. MANAGEMENT CONSIDERATIONS 



S. debilis is now known from well over a dozen sites in 

 southwest Montana. It was associated with almost every 

 alkaline meadow in the study area. Although many Montana 

 populations are small, a large percentage of those in the 

 study area are relatively large. This species' alkaline 

 meadow habitat is often along streams, and most populations 

 are subject to livestock grazing, but S. debilis was most 

 common at some of the most heavily grazed sites. It appears 

 to be able to persist under moderate and even heavy livestock 

 use. This species is not recommended further BLM 

 consideration but may be appropriate to place in the state 

 limited distribution category. 



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