(reprint from May/June 2001 Sego Lily Vol. 24 no. 3)
Rare Indeed!


By Bill King
Utah Native Plant Society

There are some 29 species of vascular plants in Utah that are federally listed as threatened, endangered or are candidates for listing as such. But there are many more species that are almost as rare or are being threatened by one cause or another.

Two such species grow in the Goose Creek Valley of the far northwest corner of Utah in Box Elder County and Cassia County in Idaho at an elevation range of about 4900 to 5700 feet. They are the Goose Creek Astragalus, Astragalus anserinus and the Idaho Penstemon, Penstemon idahoensis, which are restricted to living on hummocks of tuffaceous barren soil of the Salt Lake Formation usually in Utah juniper or big sagebrush communities. Goose Creek flows into the Snake River and is near the southern limit of the greater Columbia Basin. Both species of plants were recently described in the Great Basin Naturalist: the astragalus in 1984 by Duane Atwood, Sheryl Goodrich and Stanley Welsh and the penstemon in 1988 by Duane Atwood and Stanley Welsh.

Astragalus anserinus looks a bit like a compact form of the Utah Milkvetch, Astragalus utahensis, with gray leaves and pink to purple flowers but the sessile pods are caramel colored rather than white and hairy. Penstemon idahoensis is 3 to 8 inches tall and has blue to purple flowers that are all on one side. It is glandular and sticky all over with adhering sand grains. Both plants are very attractive and specially adapted to a unique habitat (see illustrations).

Mancuso and Mosley (1991a and b) and Baird (1991) in their surveys of these plants in 1990 gave the total known population in Utah and Idaho of Astragalus anserinus at only about 8,000 individual plants and Penstemon idahoensis at only about 7,300. Jim Morefield, Nevada Natural Heritage Program, in a personal communication in 2001, reported 827 Astragalus anserinus in Nevada, but no Penstemon idahoensis have been reported from that state. The Utah Natural Heritage Program ranks both species as S1, which indicates extreme rarity in Utah, or other factors making the species especially vulnerable to extinction or extirpation. Globally, or range wide, they rank Penstemon idahoensis as a G1 and Astragalus anserinus, which has a bit wider distribution, as a G2.

These two species are being impacted by a number of factors. Mancuso and Moseley, stated in their 1991a report on page 22 that: "Indirect impacts due to cattle grazing, such as increased erosion of fragile slopes, trampling and trailing and the construction of access roads and water tank facilities are the principle existing threats to Goose Creek Milkvetch" and they said much the same thing about the Idaho Penstemon (Mancuso and Moseley, 1991b, page 19). A recent proposal by the BLM to build a four and one half mile water pipeline and new cattle troughs near known populations of these two rare plants could aggravate the situation.

Other impacts threaten these species, aggressive leafy spurge, Euphorbia esula, has been reported to be invading some of the Idaho populations. Idaho agencies have removed the spurge from some of the areas but others remain. Most of this area has also been designated by the BLM as open to off highway vehicle (OHV) use where cross country travel is permitted by all types of vehicles at all times. The dramatic increase in OHV in Utah could pose a threat to these rare species. Furthermore, the Goose Creek fires of August, 2000 over ran some of the known populations of A. anserinus.

What is needed here is an updated survey of Utah’s populations of Astragalus anserinus and Penstemon idahoensis to determine what impact the many threats to these plants may be having and, if need be, a plan or conservation agreement should be implemented to prevent these two species from becoming endangered.

Selected References:

Baird, G. I. 1991, "Report for 1990 Challenge Cost Share Project, USDI Bureau of Land Management. Target Species: Astragalus anserinus Atwood, Goodrich, & Welsh, Penstemon idahoensis Atwood & Welsh, Potentillia cottamii Holmgren".

Mancuso, M. and R. Moseley. 1991a. "Report on the Conservation Status of Astragalus anserinus, Idaho Department of Fish and Game, Conservation Data Center, Boise, Idaho".

Mancuso, M. and R. Moseley. 1991b. "Report on the Conservation Status of Penstemon idahoensis, in Idaho and Utah, Idaho Department of Fish and Game, Conservation Data Center, Boise, Idaho".

Copyright 2001 Utah Native Plant Society