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U.S. Forest Service

Plant of the Week

Cypripedium fasciculatum, Parry’s agave, range map. Cypripedium fasciculatum range map. USDA PLANTS Database.

Clump of Clustered Lady's Slipper orchids. Classic clump of Clustered Lady's Slipper orchids. Photo by Matt Brown.

Clustered Lady's Slipper flowers. Clustered Lady's Slipper flowers. Photo by Matt Brown.

Clustered Lady’s Slipper (Cypripedium fasciculatum Kellogg ex S. Watson)

By Matt Brown

The clustered lady’s slipper is a terrestrial orchid native to Western North America. This unique orchid is often found growing in cool seasonally dry mountain slopes or moist stream terraces, often in partially to fully shaded coniferous forest. The orchid is rather uncommon, occurring in small isolated populations from Washington to northern California and east in the mountains of Idaho, Montana, Wyoming, Utah, and Colorado. Currently the U.S. Forest Service protects C. fasciculatum on all National Forests where the orchid occurs.

The clustered lady’s slipper is a member of the Orchid family (Orchidaceae) and can be easily identified in spring and early summer by its distinct flower that forms an inflated lip or “slipper” which is the namesake for the genus. Flower color ranges from brown markings on a green or golden background to complete brown, appearing to be nearly red. The orchid has two opposite elliptical leaves borne on a short stem (5-20 cm), and tends to form small clusters of 5-10 stems on the forest floor often under the cool shade of dogwoods or other forest shrubs.

The dust-like seeds of most orchids, including the clustered lady’s slipper, are unique compared to most plants because the seeds are underdeveloped when mature, lacking roots, leaves, and chlorophyll. The seeds remain partially or entirely inactive after being dispersed, until the seed is invaded by hyphae of fungi found in the soil. The seedling then enlarges and forms a bulb like structure that eventually gives rise to photosynthetic tissue and finally a mature plant. For the clustered lady’s slipper, this process is believed to take up to three years, which means that for the first three years the orchid seedling is subterranean and completely dependent on soil fungi for water, carbohydrates, and nutrients (heterotrophic). In the association between the soil fungus and the orchid, the fungus degrades cellulose in leaf litter and coverts it into sugar, which is used by the developing orchid. Some have gone so far as to suggest that the orchid seedling is actually parasitizing the soil fungi, however it is currently unknown if the soil fungus receives anything in return from associating with the orchid.

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