Flora of North America species comparison

P. A. Rydberg (1898) used var. alpicola (as Horkelia gordonii var. alpicola) for compact, high-elevation plants throughout the range of Ivesia gordonii. As circumscribed here, var. alpicola is restricted to plants occurring disjunctly in an arc around the northwestern part of the species range. Populations occur in the northern Coast Ranges and central Sierra Nevada of California, sporadically to Mount Adams and the Wenatchee Mountains in Washington, and from there to the mountains of central Idaho and the Bitterroot Range of Montana. The variety is also disjunct on the Owyhee Mountains of southwestern Idaho.

Plants of var. alpicola average shorter than those of var. gordonii, which occurs farther east and south. In var. alpicola, stems with only glandular indumentum are common; such stems are rare in var. gordonii. Unlike those of var. gordonii, the leaflets of var. alpicola are frequently glandular with only marginal hairs.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

As circumscribed here, var. ursinorum encompasses “tenuicaulis” of N. H. Holmgren (1997b) but is more broadly defined to encompass generally prostrate to decumbent plants found at widely scattered locations in and adjacent to the northwestern Intermountain Region. Such plants are most common in the Independence and Jarbidge mountains (Elko County, Nevada) and on Steens Mountain and other ranges in southeastern Oregon. Similar plants dominate the mountains of central Idaho and the Wallowa Mountains of Oregon, mostly south of var. alpicola. In northern California, var. ursinorum is found on the Modoc, Scott, and Sweetwater mountains, and around Sonora Pass in the Sierra Nevada.

In general, var. ursinorum may be distinguished from var. alpicola by its more commonly prostrate to ascending habit, reddish stems, narrowly cylindric (bottlebrushlike) leaves, and rounder leaflet lobes. The inflorescence is also more prone to becoming lax at maturity. Plants are most often glandular-pubescent and minutely glandular but otherwise glabrate, the conspicuous exception being the type of var. ursinorum from northern California. Plants in the Wallowa Mountains approach var. alpicola, as do some populations in California and central Idaho, where they are sometimes only tentatively assigned to one variety or the other. Some central Idaho collections included here in var. ursinorum have more cupulate hypanthia and wider petals approaching those of Ivesia lycopodioides.

(Discussion copyrighted by Flora of North America; reprinted with permission.)