Branched phacelia (Phacelia ramosissima) COSEWIC assessment and status report: chapter 4

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Distribution

Global range

Phacelia ramosissima occurs in western North America, from the southern Okanagan Valley in south-central British Columbia south through Washington and Oregon to Nevada and southern California (Figure 3, Wilken et al. 1993, Douglas et al. 1999a, Kartesz 1999). The nearest population in Washington State is about 175 km south of the Osoyoos localities in Chelan County, just south of Entiat (D. Giblin, pers. comm.)

Canadian range

In British Columbia, Phacelia ramosissimahas been collected or observed at 12 sites on the slopes of Mount Kruger, near Osoyoos, in the southern Okanagan Valley (Figure 4). The first collection of this species in British Columbia was recorded by H. Moore in 1986. George W. Douglas and Shyanne J. Smith searched a number of apparently suitable habitats throughout the southern Okanagan Valley and the southern Similkameen valley in 2003 and located only three new sites. One previously reported site was reconfirmed and two subpopulations were determined to have been extirpated.  The search effort would appear to be sufficient since George W. Douglas has searched most (approximately 80%) of the 6100 ha of potential habitat (Figure 5) at various times over the past 12 years.

Phacelia ramosissima is just one of a number of species recently discovered (since the 1980’s) along the British Columbia border from the Princeton area to the Roosville area. Some of these species include: Antennaria flagellaris, Carex vallicola, Collomia tenellus, Floerkea proserpinacoides, Hedeoma hispida, Lipocarpha micrantha, Orobanche ludoviciana, Orthocarpus barbatus, Psilocarphus brevissimus, Silene spaldingii and Trichostema oblongum (Douglas et al. 1998a, b). Most of these species have at least one thing in common; the areas in which they were found were never subjected to botanical collecting. Examination of collection localities in all major herbaria in Canada reveal that none of the many active field botanists working along the border in British Columbia ever collected in the immediate vicinity of the recently collected plants. In the case of P. ramosissima in British Columbia, the dry rocky slopes on which it occurs are also the habitat of extremely high numbers of rattlesnakes. This presence of rattlesnakes and the low plant diversity of these slopes discourage most potential visitors (even keen botanists) during spring or summer.