29 



3. Soil relations: As its name suggests, rock-tansy grows out 

 of cracks in rock pavement and in shallow, poorly developed 

 lithosols. At least in Montana and Utah (Welsh 1987) the 

 parent material is limestone. 



E. Population demography and biology 



1. Demographic details: The two populations in the study area 

 were estimated to consist of between 100 and 500 plants 

 each. 



2. Reproductive biology: Plants are probably quite long lived; 

 all observed were mature, reproductive adults. Plants were 

 in a flower bud stage at both survey dates in June. 



E. Management considerations: 



Sphaeromeria capitata is probably fairly common on limestone 

 outcrops around Clark Canyon Reservoir. It is abundant on the 

 south side of the Pryor Mountains, where 16 populations were 

 discovered in 1991 (Lesica and Achuff 1992), and is common with a 

 wide distribution in Wyoming. The limestone outcrop habitat is 

 not generally threatened except possibly by mining, and the 

 plants tough and low growing habit make it resistant to grazing 

 and trampling. No special BLM status is recommended for this 

 plant. Rock-tansy should be considered a species of limited 

 distribution in Montana, but should not continue to be actively 

 tracked by the Montana Natural Heritage Program. 



