Rare Plants of the Boise Foothills

Many things make Boise a special place to live, one of them being its proximity to the foothills. Over a century of pressure of being adjacent to Idaho’s largest city Boise has taken its toll on native habitats, however. Development, heavy recreational use, invasive species and more, has resulted in a marked decline in biodiversity of the Boise foothills over the last ten years (Moseley et al. 1992). This trend is particularly evident in the status of four rare plants:

The U.S. Fish and Wildlife Service (USFWS), City of Boise (COB), and Ada County developed a Boise Foothills Conservation Agreement (Conservation Agreement) for three of the rare plant species - Aase’s onion, Mulford’s milkvetch (Astragalus mulfordiae), and slickspot peppergrass (Lepidium papilliferum) in 1996 and revised the agreement in 2008. Boise sand-verbena had not yet been identified as its own unique species. The Conservation Agreement was put in place to help protect and ensure the long-term conservation of the three species and their habitats on property owned by Boise City, foothill properties with conservation easements held by Boise City, and the Ada County Sanitary Landfill (U.S. Fish and Wildlife Service 2008).

Monitoring for rare plants is on-going on city property, and in partnership with the Idaho Native Plant Society – Pahove Chapter. The goal of the program is to collect rare plant population and habitat information to understand and evaluate population abundance and habitat condition trends (possible trend outcomes include stable, increasing, decreasing, or fluctuating). The objective for the monitoring program is to provide COB land managers with information that will allow them to assess the conservation status of rare plants and inform any conservation actions that may be needed. Trend information will be used to prioritize invasive species management treatments, inform locations where additional signage is needed to educate the public about conservation efforts, and other possible pro-active conservation measures.