Page authors: Don Knoke, David Giblin
Asclepias cryptoceras
Humboldt milkweed, pallid milkweed

Distribution: Occurring east of the Cascades crest in southeastern Washington; southeastern Washington to California, east to Idaho, Wyoming, and Colorado.

Habitat: Gravelly to heavy clay soil in the foothills and lower mountains.

Flowers: April-June

Origin: Native

Growth Duration: Perennial

Conservation Status: Threatened in Washington (WANHP)

Pollination: Bumblebees, bees, butterflies, beetles, wasps


Herbaceous, rather fleshy perennial from a large, woody root, the stems prostrate or decumbent, 1-3 dm. long.


Leaves opposite, obovate to oval, 2-6 cm. long and nearly as broad, glabrous except for small, marginal hairs.


Inflorescence usually of terminal umbels, the central one 5-10 flowered, with peduncle and pedicles 2-4 cm. long, the lateral ones few-flowered and sessile; sepals 5, linear to lanceolate, 5-9 mm. long, green, with long, fine, tangled hairs; corolla pale greenish-yellow, the 5 lobes lanceolate, 8-12 mm. long, reddish tinged on the back, reflexed; stamens 5, attached to the base of the corolla tube and to each other, forming a column, to which are attached saccate structures, pinkish, bi-lobed above, the lobes projecting into erect teeth that exceed the anthers; pistil 1, 2-carpellary, the ovaries superior and distinct.


Follicles ovoid, 3-5 cm. long, smooth.

Accepted Name:
Asclepias cryptoceras S. Watson
Publication: Botany Fortieth Parallel 283, pl. 28, f. 1-4. 1871.

Synonyms & Misapplications:
Asclepias cryptoceras S. Watson ssp. davisii (Woodson) Woodson [KZ99]
Asclepias cryptoceras S. Watson var. davisii (Woodson) W.H. Baker
Asclepias davisii Woodson
Additional Resources:

PNW Herbaria: Specimen records of Asclepias cryptoceras in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Asclepias cryptoceras checklist entry.

OregonFlora: Asclepias cryptoceras information.

E-Flora BC: Asclepias cryptoceras atlas page.

CalPhotos: Asclepias cryptoceras photos.

USDA Plants: Asclepias cryptoceras information.

26 photographs:
Group by