Mapping Castilleja christii (Christ’s paintbrush) on Mount Harrison, Cassia County, Idaho

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Castilleja christii (Christ’s paintbrush) is a perennial forb known from a single occurrence in southern Idaho. It is endemic to the top of Mount Harrison, the third highest peak in the Albion Mountains, Cassia County, where it inhabits subalpine plant communities dominated by forbs, graminoids, and shrubs. Castilleja christii was designated as a candidate for threatened and endangered listing in 1980 and removed from candidate status in 2012. Because it is one of Idaho’s rarest plants, it remains a high priority for the US Fish and Wildlife Service, US Forest Service, and Idaho Department of Fish and Game. Prior to mapping, all surveyors were familiar with the identification of Castilleja christii and the two look-alikes C. linariifolia (Wyoming paintbrush) and C. miniata (scarlet paintbrush, giant red paintbrush) known from the highest parts of Mount Harrison, as well as C. pallescens and C. angustifolia, which are known from nearby areas. In late July to early August 2016 and 2017, we mapped the perimeters of the main occurrence and two disjunct occurrences. We walked a meandering route along the perimeters searching for the outermost C. christii plants. Our perimeter routes totaled 32.3 km (20.1 mi). For each individual or cluster of plants observed along the perimeter, we recorded a waypoint using a handheld Garmin GPS unit. In 2018, we walked an interior route south and east of Howell Canyon Road to determine if the main occurrence was non-continuous as previously mapped in 1993, and we found that the area was occupied continuously. We also surveyed for C. christii north and south of the main occurrence, where the associate Cymopterus davisii (Davis’ wavewing) had been mapped in prior years. C. davisii is a rare endemic known from Mount Harrison and nearby peaks. No new disjunct occurrences of C. christii were found. Our survey routes totaled 7.6 km (4.7 mi). We found C. christii at elevations of 2621 to 2810 m (8600 to 9220 ft). The total area mapped as occupied by C. christii was 65.5 ha (161.9 ac), which was essentially the same total area—66.8 ha (164.9 ac)—that had been hand-mapped in 1993. Some differences in occupied regions are apparent in comparing the two maps. We recommend remapping the occurrence in about 10 years to assess potential change in the size of the main occurrence or the two small disjunct occurrences. We also recommend revisiting a few spots along the perimeter where we were uncertain of the species identification of some Castilleja plants that appeared intermediate between C. christii and congeners in the area.

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Reference Code: U20MIL04IDUS <br>

Full Citation: Miller, J.J., and C.L. Kinter. 2020. Mapping Castilleja christii (Christ’s paintbrush) on Mount Harrison, Cassia County, Idaho. Idaho Natural Heritage Program, Idaho Department of Fish and Game, Boise, ID. 26 pp. plus appendices. <br>

Location: ELECTRONIC FILE - BOTANY: PLANT SPECIES: Castilleja christii <br>

Keywords: Castilleja christii, Christ’s paintbrush, Cymopterus davisii, Davis’ wavewing, Albion Mountains, Mount Harrison, rare plant conservation, Idaho, endemic species, occurrence, habitat <br>