> 



20 



C. Phenology. 



1. Patterns: In Montana, the flowering period for 

 C. lonqistylum starts near the end of June, 

 peaks in July and extends into August. 

 Flowering occurs basipetally in C. longistyluin , 

 with the lowermost flowering heads developing 

 last. Seeds mature in August and September, 

 and are primarily wind dispersed. Seeds of 

 this species have been germinated successfully 

 without cold stratification or scarification 



(Sarah Mathews, pers. comm.), and therefore may 

 germinate in the fall. 



2. Relation to climate and microclimate: Plants 

 occurring at lower elevations, and on more 

 southerly slopes begin to flower two to three 

 weeks before plants occurring at the higher 

 elevations. This may be important with respect 

 to weevil infestations, since timing of egg- 

 laying by Rhinocyllus conicus is related to 

 temperature, and higher elevation sites have 

 extremes in temperature fluctuations (Dr. 

 Charles Turner, pers. comm.). 



D. Reproductive ecology. 



1. Types of reproduction: Cirsium lonqistylum 



reproduces both asexually by biennial offsets 

 from a perennial rhizome (Moore and Frankton 

 1963), and sexually by seeds produced from 

 perfect flowers. Observations of populations 

 indicate a good range of plants at each life 

 history stage, from single whorl rosette, 

 through larger multiple whorl rosettes, to 

 flowering and fruiting adults. It is not yet 

 certain that this species is a strict biennial; 

 small (single whorl) to large (multiple whorl) 

 rosettes were observed in populations as well 

 as flowering plants. Results of demographic 

 monitoring studies begun in 1990 should give a 

 better indication of these life history as 

 traits exhibited by this species. 



2. Pollination. 



a. Mechanisms: Cirsium lonqistylum is known 

 to be insect pollinated. Whether self- 

 pollination occurs is not known. 



> 



