Page authors: David Giblin, Don Knoke
Petrophytum cinerascens
Chelan rockmat

Distribution: Occurring east of the Cascades crest, where endemic to the Columbia River region of central Washington.

Habitat: Basaltic cliffs.

Flowers: June-August

Origin: Native

Conservation Status: Endangered in Washington (WANHP)


Prostrate, matted sub-shrub.


Leaves oblanceolate-spatulate, 15-25 mm. long and 2-4 mm. broad, 3-nerved, sparsely appressed-pubescent.


Inflorescence a tight, spikelike, bracteate raceme 2-6 cm. long on a peduncle 5-15 cm. tall, with scattered, bract-like leaves below and more numerous linear, acute bracts above bearing rudimentary buds; pedicles 0.5-2 mm. long; calyx grayish-sericeous, top-shaped, 1 mm. long, with 5 triangular-lanceolate, erect lobes 1.5 mm. long; petals narrowly oblanceolate with a wedge-shaped base, scarcely exceeding the sepals; stamens 20-25; pistils 5, the styles slender, 2 mm. long.


Follicles nearly 3 mm. long.

Accepted Name:
Petrophytum cinerascens (Piper) Rydb.
Publication: North American Flora 22(3): 253. 1908.

Synonyms & Misapplications:
Petrophyton cinerascens (Piper) Rydb., orthographic variant
Spiraea cinerascens Piper
Additional Resources:

PNW Herbaria: Specimen records of Petrophytum cinerascens in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Petrophytum cinerascens checklist entry.

E-Flora BC: Petrophytum cinerascens atlas page.

CalPhotos: Petrophytum cinerascens photos.

USDA Plants: Petrophytum cinerascens information.

5 photographs:
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