17 



acres. In 1993, thousands of plants were observed with a 

 more or less continuous distribution for miles on a belt of 

 limestone to the south of Clark Canyon Reservoir (007). In 

 1994, the population to the north of Clark Canyon Reservoir 

 was estimated to consist of 100 to 500 plants and to cover 

 at least 40 acres. 



2. Reproductive biology: Reproduction is by seed. The 



flowering period is May- June. Mature fruit have been noted 

 at only a few sites in the state, however, this is because 

 the taxon has been surveyed only at early dates; without 

 flowers, Delphinium bicolor ssp. cannot be distinguished 

 from the nominate subspecies, at least given current 

 knowledge of the taxon. Many populations have a large 

 proportion of vegetative plants (presumably juvenile), which 

 is taken as an indication of successful reproduction and 

 seedling establishment. Although larkspur species are known 

 to hybridize, no intermediates between the subspecies have 

 been seen, even when the two taxa were growing close 

 together. 



F. Management concerns: 



Recent studies in Montana have shown that what was previously 

 tracked as two separate species (Delphinium andersonii and 

 Delphinium geyeri) is better treated as one taxon, which will be 

 described as a subspecies of Delphinium bicolor (Warnock, in 

 preparation). In addition, many new populations of the taxon 

 have been recently discovered and its distribution in many areas 

 has been found to be more or less continuous over large areas of 

 suitable habitat. The taxon is, thus, now known to be much more 

 common than was thought just a couple of years ago. Populations 

 seem to respond well to grazing; at one site near Doherty 

 Mountain, in Jefferson County, a population which straddled a 

 fenceline was more dense on the heavily grazed side, and 

 flourishing populations have been observed elsewhere in grazed 

 habitat. Other populations, including those in this study area 

 around Clark Canyon Reservoir, occur in secondary range. Species 

 of Delphinium are known to be toxic to cattle. It now seems that 

 management for conservation of Limestone larkspur is not 

 necessary and no special BLM status is proposed. The taxon does 

 have special significance because it is a very attractive Montana 

 endemic. Although this species is now known to be too common to 

 warrant continued tracking by the Montana Natural Heritage 

 Program, it is appropriately placed on lists of state endemics 

 and species of limited distribution. 



