The stream orchid or false helleborine orchid (Epipactis gigantea) is a critically imperiled plant that occurs at Filoha Meadows Nature Preserve in Pitkin County, Colorado. This report documents the fourth year of a longterm monitoring study tracking annual population trends of this orchid. In 2021, the density of the overall orchid population at Filoha was slightly less than in 2019 and 2020, but still higher than 2018. Orchid density appears to be highly correlated with precipitation patterns the preceding winter and spring, with lower densities observed in hot dry years. However spatial variation in orchid density occurs across the landscape with some locations having higher densities than others. Overall, the orchid population at Filoha appears to be stable and the culmination of this four-year study provides important baseline information upon which future monitoring can be compared.

This report also documents the lack of any adverse effects to the stream orchid density from Canada thistle (Cirsium arvense) control efforts which included both herbicide and
mechanical (hand-pulling) treatments.