Page author: David Giblin
Ivesia tweedyi
Tweedy's mousetail

Distribution: Occurring east of the Cascades crest in Washington; Washington to Idaho and Montana.

Habitat: Dry, open to wooded areas, middle to high elevations in the mountains.

Flowers: June-August

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern


Herbaceous perennial from a strong taproot, the flowering stems 5-20 cm. tall, nearly glabrous below and glandular-pubescent above.


Basal leaves numerous, the blades 3-8 cm. long, pinnate, the leaflets 19-35, less than 1 cm. long, dissected into many filiform or linear segments; cauline leaves 1-3, greatly reduced, the stipules well developed.


Inflorescence a congested, terminal cluster; calyx bowl-shaped, yellowish-green, the 5 lobes deltoid-ovate, yellowish, 2.5-3 mm. long; petals 5, yellow, elliptic to spatulate, longer than the sepals; stamens 5, pistils 4-6.


Achenes 2 mm. long, smooth.

Accepted Name:
Ivesia tweedyi Rydb.
Publication: North American Flora 22(3): 288. 1908.

Synonyms & Misapplications:
Horkelia tweedyi Nels & Macbr. var. alpicola Rydb.
Potentilla tweedyi (Rydb.) J.T. Howell
Additional Resources:

PNW Herbaria: Specimen records of Ivesia tweedyi in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Ivesia tweedyi checklist entry.

E-Flora BC: Ivesia tweedyi atlas page.

CalPhotos: Ivesia tweedyi photos.

USDA Plants: Ivesia tweedyi information.

20 photographs:
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