''Ivesia tweedyi'', Tweedy's mousetail or Tweedy's ivesia, is a perennial herb in the

rose family Rosaceae (), the rose family, is a medium-sized family of flowering plants that includes 4,828 known species in 91 genera. The name is derived from the type genus ''Rosa''. Among the most species-rich genera are ''Alchemilla'' (270), ''Sorbus' ...

. It is native to the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

in the United States, from

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered on ...

east to westernmost

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

Taxonomy

''Ivesia tweedyi'' was described and published in 1908 by

Per Axel Rydberg Per Axel Rydberg (July 6, 1860 – July 25, 1931) was a Swedish-born, American botanist who was the first curator of the New York Botanical Garden Herbarium. Biography Per Axel Rydberg was born in Odh, Västergötland, Sweden and emigrated to t ...

, who named it in honor of

Frank Tweedy Frank Tweedy (1854–1937) was an American topographer and botanist. He worked on pioneering surveys first in the Adirondacks, and then in the American West. He also made major contributions to our knowledge of the western flora and vegetation. H ...

, the first to collect it. Tweedy's specimen, the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, is deposited at the New York Botanical Garden Steere Herbarium.''Ivesia Tweedyi'' holotype, NY
/ref>

Aven Nelson Aven Nelson (March 24, 1859 – March 31, 1952) was an American botanist who specialized in plants of the Rocky Mountains. He was one of the founding professors of the University of Wyoming, where he taught for 55 years as professor and served as ...

and James Francis McBride reclassified ''Ivesia tweedyi'' as ''Horkelia tweedyi'' in 1916, but this name was not generally accepted. Botanist

John Thomas Howell John Thomas Howell (November 6, 1903 – May 7, 1994) was an American botanist and taxonomist. He became an expert of ''Eriogonum'' (buckwheat) species, which are widely represented in the native California flora. He was the assistant of Alice ...

transferred Tweedy's mousetail to ''Potentilla tweedyi'' in 1945. ''Ivesia tweedyi'' is the currently accepted name."Ivesia tweedyi" in Flora of North America
/ref>

Description

''Ivesia tweedyi'' is a perennial herb to from a stout taproot. It has finely-dissected, pinnate basal leaves which often lie somewhat flat, appearing to radiate from the central root crown. The reddish or purplish stems are glandular and usually finely hairy above, each with 1 to 3 small leaves and topped with a cluster of several flowers. Each flower has five yellow petals surrounded by a shallow bowl-shaped hypanthium.Mosely, RK. 1993. Floristic inventory of subalpine parks in the Coeur D'Alene River drainage, northern Idaho. P. 23.
/ref> ''Ivesia tweedyi'' is similar to '' Ivesia gordonii'', with which it cooccurs in the

. However, the latter is much more widespread. The finely-dissected flat-lying basal leaves of Tweedy's ivesia are a useful distinguishing character. Also, its petals are oblanceolate or spoon shaped (spatulate) or even broadly obovate, and wider than the petals of ''I. gordonii'', which are narrowly lanceolate or narrowly spatulate at most. The "mousetail" in the common name refers to the cylindric arrangement of the many small leaflets around the leaf

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

Distribution and habitat

''Ivesia tweedyi'' is endemic to the

in the United States, growing in central and northeastern

, northern

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...

, and northwestern-most

(Mineral County).Tweedy's Ivesia, Montana Field Guide
/ref>''Ivesia tweedyi'' in Burke Herbarium Image Collection
/ref> It grows on dry, gravelly to rocky flats, slopes, alpine ridges, and in subalpine conifer woodlands. It is notable for its occurrence on serpentine.

Conservation status

Tweedy's ivesia is ranked G4, i.e., apparently secure overall. It is of state conservation concern in

History

named ''Ivesia tweedyi'' in honor of

, who made the first collection, in the Yakima area of Washington Territory in 1883. At that time Tweedy was working as a topographer on the Northern Transcontinental Survey.

Cultivation

Tweedy's ivesia is suitable for rock gardens. It does best in dry sunny spots "with a good rock to cover the taproot".Kruckeberg, A.R., & Chalker-Scott, L. 2019. Gardening with Native Plants of the Pacific Northwest, 2nd ed. U. Washington Press. P. 197

References

{{Taxonbar, from=Q17271287 tweedyi Flora of the United States Plants described in 1908