Search / Plant Profile / Trifolium thompsonii

Plant Profile

Thompson's Clover (Trifolium thompsonii)

Trifolium thompsonii is an integral part of this striking landscape. Photo Credit: Ed Guerrant

Global Rank: G2 - Imperiled
Legal Status: N/A
Family: Fabaceae
State: WA
Nature Serve ID: 148240
Lifeform: Forb/herb
Date Inducted in National Collection: 04/04/1991

Description:

Trifolium thompsonii probably doesn't look like any other clover you've ever seen. It grows up to two feet tall and its large, spherical, reddish-lavender flower heads rise above the swaying grass like a sea of cheerleader pom-poms. Unlike most clovers, the leaves of this plant are comprised of 3 to 8 narrow, pointed leaflets (most clovers have three leaflets, hence the name "trifolium" or "three leaves"). It grows only within a fairly limited geographical distribution (only 20 miles north to south), but Trifolium thompsonii can be found in a wide variety of habitats. It grows in open ponderosa pine woods, grass and herb dominated areas, and sagebrush steppe. Steep slopes, along ridgelines, in alluvial fans and along canyon bottoms anywhere from 140 feet to 3760 feet (40m to 1130 m) in elevation are likely places to find this species.

Where is Thompson's Clover (Trifolium thompsonii) located in the wild?

Habitat:

Trifolium thompsonii grows in a wide variety to habitats. The majority of populations grow on the fringe of the ponderosa pine (Pinus ponderosa) zone in open ponderosa pine woods or grass and herb dominated areas. It grows along ridgelines, on steep slopes, in alluvial fans, and in canyon bottoms anywhere from 140 feet to 2760 feet (40 m to 1130 m).

Distribution:

WA: Columbia Basin, Eastern Cascades. Chelan County and Douglas County, WA.

States & Provinces:

Thompson's Clover can be found in Washington

Which CPC Partners conserve Thompson's Clover (Trifolium thompsonii)?

University Of Washington Botanic Gardens

Not Sponsored

Assigned 06/09/17

Rae Selling Berry Seed Bank & Plant Conservation Program

Not Sponsored

Conservation Actions

Assigned 08/07/19

CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

Conservation Actions

10/01/2020

Germination trials at The Berry Botanic Garden were inconclusive. Seeds were subjected to either 8 weeks of cold stratification or no cold stratification followed by either constant 68F (20C) or alternating 50 /68F (10/20C) temperatures. Without cold stratification, both temperature treatments showed 40% germination. With cold stratification, the constant 68F treatments showed 40% germination while the alternating 50/68F treatment showed 80% germination (BBG File).

10/01/2020

10/01/2020

10/01/2020

Nature Serve Biotics

05/02/2017

Endemic to Chelan and adjacent Douglas counties in Washington State. There are 14 occurrences known extant (although the number of reproductively isolated populations may be much smaller). Conversion to orchards, range degradation, and fire suppression leading to conifer invasion of the grasslands are all on-going threats. Invasions of noxious weeds, and subsequent efforts to control them, also pose threats.

Edward Guerrant, Ph.D.

01/01/2010

Threats include (in WNHP 1999): The invasion of exotic species such as knapweed (Centaurea diffusa) and cheatgrass (Bromus tectorum). Agricultural conversion. Livestock grazing. Illegal ORV use in population areas.

Edward Guerrant, Ph.D.

01/01/2010

Approximately 15 sites have been observed since 1986. Numbers range from as low as 30-40 to as high as several thousand per site. 11 of the known sites are on Forest Service Land (WNHP 2000).

Edward Guerrant, Ph.D.

01/01/2010

Comprehensive study of the ecological life history of Trifolium thompsonii. Geology, soil characteristics, phenology and morphology, floral biology, seed biology, predation, effects of fire, interactions with cheat grass (Bromus tectorum), population dynamics and effects of cover on the taxon were all investigated (Canfield 1977). Germination trials at The Berry Botanic Garden were inconclusive. Seeds were subjected to either 8 weeks of cold stratification or no cold stratification followed by either constant 68F (20C) or alternating 50 /68F (10/20C) temperatures. Without cold stratification, both temperature treatments showed 40% germination. With cold stratification, the constant 68F treatments showed 40% germination while the alternating 50/68F treatment showed 80% germination (BBG File).

Edward Guerrant, Ph.D.

01/01/2010

A proposal was made in 1975 to designate an area to help preserve this taxon. This resulted in the establishment of the Thompson Clover Natural Research Area in 1977 by the U.S. Forest Service.

Edward Guerrant, Ph.D.

01/01/2010

Search suitable habitats in Douglas and Chelan County for populations (WNHP 1999). Study potential factors influencing the limited distribution of Trifolium thompsonii.

Edward Guerrant, Ph.D.

01/01/2010

Collect and store seeds from across the known range. Collect from a variety of habitats and elevations. Determine optimum germination conditions. Test conditions corresponding to natural elevation and habitat gradients for this species. Determine propagation and reintroduction protocols.