10 



SOIL RELATIONSHIPS: Limestone larkspur occupies shallow, 

 gravelly soils usually overlying limestone outcrop but also found 

 on alluvial sand in the Boulder Valley and locally on thin soils 

 overlying sandstone. In all of these settings, regardless of 

 topographic position, soils are droughty and calcareous. 



CLIMATE FACTORS: This species is among the majority of species 

 in the local flora that flowers and reaches peak growth early in 

 the growing season, coinciding with the peak precipitation and 

 mild temperatures of spring before extreme heat and drought of 

 summer. 



POPULATION DEMOGRAPHY AND BIOLOGY 



PHENOLOGY: Plants were in full bloom in late May and early June, 

 with one or more mature flowers. Most inf loresences only had 2-5 

 flowers. 



POPULATION SIZE AND CONDITION: In the study area, limestone 

 larkspur were usually in low densities, distributed in patches, 

 with less than 20 flowering plants per acre. There were more 

 nonf lowering plants compared to flowering plants. The Elkhorns 

 populations were incompletely surveyed because they extended off 

 of public land onto lower elevation private lands where they seem 

 to have their center. Providing some basis for estimation, 

 Vanderhorst and Lesica (1994) characterize the Tendoy Mountains 

 populations as typically large, ranking between 200-10,000 

 plants. 



REPRODUCTIVE BIOLOGY: Larkspurs are adapted for pollination by 

 insects, with the upper sepal modified into a nectar-bearing spur 

 that lures visitors. 



G. POPULATION ECOLOGY 



1. BIOLOGICAL INTERACTIONS 



a. COMPETITION: Limestone larkspur is considered to be a poor 

 competitor, occupying some of the most sparsely-vegetated ridges 

 in the study area. It was also observed in early-successional 

 settings like readouts. The spot invasion of noxious weeds poses 

 the immediate and most insidious potential threat to its habitat. 



b. HERBIVORY: Larkspurs are known to be toxic to cattle, 

 particularly the species which are taller and late-flowering. 

 Limestone larkspur has been observed in heavily-grazed areas 

 where it appears resistant or even favored by grazing 

 (Vanderhorst 1993) . In the study area, this plant occupies 

 secondary range having little or no livestock use, but it may 

 still be an "increaser" under some circumstances. 



