Clustered lady’s slipper (Cypripedium fasciculatum Kellogg ex S. Watson; synonym includes Cypripedium knightiae A. Nelson) is considered a candidate for listing by the Oregon Department of Agriculture, a Federal Species of Concern, and a Heritage List 2 species (threatened with extirpation in Oregon; ORBIC 2010). This orchid is rare throughout its range in the western United States. More than 800 locations for clustered lady’s slipper have been identified in the Medford District BLM. Many of these populations had ten or fewer individuals at their last survey date but the current status of most of these populations is unknown. Small populations may be normal and healthy in this species or they may be at an elevated risk of extirpation. In an analysis of clustered lady’s slipper and mountain lady’s slipper (Cypripedium montanum) populations in California, we found that over the period of time follow-up observations were made (1 to 23 years), approximately 66% of populations declined in size and 30% – 45% fell to zero (Kaye and Cramer 2005). Both population size and time since previous observation were significantly correlated with extinction events.
The purpose of this project was to survey populations of clustered lady’s slipper in the Medford District BLM in order to expand on this earlier analysis and better model the probability of extinction [Population Viability Analysis (PVA)] for this species.