Abstract
The vascular flora described here covers ~2,295 km2 (~886 mi2) of the Selkirk mountains that lie in the Idaho Panhandle, covering an elevational range from 540–2330 m (1,770–7,670 ft.). The majority of the mountain range is underlain by granitic rock of the Kaniksu Batholith, and is diversified by the rich glacial history of the Panhandle. The study area contains multiple pockets of alluvial and glacial deposition that serve as specialized habitat for present day floristic diversity within the range. The study area is classified as the Northern Rocky Mountains, with floristic influence from the Pacific coast, boreal north, the Columbia Basin, and the Rocky Mountains to the south and east. Despite notable collection interest over the last century in the northern Idaho Panhandle, a comprehensive checklist did not exist prior to this project, and previous collecting efforts were uneven, creating significant gaps in coverage and poor documentation of the area. A total of 108 collection days were spent in the field in 2019 and 2020, resulting in 4,153 vascular plant collections, from 633 collection sites, documenting 844 total unique taxa in 94 plant families. Taxa that were previously collected but not recovered during this study were first verified by the author using historical specimens housed at multiple Pacific Northwest herbaria, and were then included in the final checklist. Fifty-four rare taxa and six state collection records were found in the study area, as well as range extensions and county collection records. While the primary objective for this study was to document and voucher all vascular plants of the Selkirk Mountains of Idaho to create an annotated checklist of the vascular flora, additional objectives included an assessment of the vegetation of the study area, and threats to the flora of the study area, as well as increasing documentation of sensitive, rare, and non-native species occurrences within the range.