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Petrophytum hendersonii

Olympic Mountain rockmat

Habit Shrubs, 2–9 dm diam.
Stems

decumbent to ascending, 1–10 cm, internodes 0.5–1.5 cm.

Leaves

blade narrowly obtrullate, sometimes oblanceolate to spatulate-obovate, 1–2(–3) × 0.2–0.6 cm, palmately 3-veined, venation visible through hairs, apex acute, abaxial surface sparsely strigose, pilose to pilose-sericeous, sometimes glabrate, sparsely strigose along veins.

Panicles

densely racemose, 2–5 × 1–2 cm, sparsely sericeous;

bracts linear, 2–4(–6) mm, pilose.

Pedicels

2–5 mm;

bracteoles 1, rarely extending to base of sepals.

Flowers

3–5 mm diam.;

hypanthium 0.5–1 mm, sparsely pilose;

sepals reflexed, oblong to obtuse, 1–1.5 mm, margins ciliate, abaxial surface sparsely pilose;

petals oval, oblong, or obovate, 2–2.5 mm, apex obtuse, sometimes 2-lobate;

stamens 25–40, lengths 1–1.3 times petals (2 times sepals);

carpels (4–)5(–6), abaxially connate.

Follicles

1.5–2 mm.

2n

= 18.

Petrophytum hendersonii

Phenology Flowering Jul–Sep.
Habitat Rock outcrops, cliffs, talus slopes
Elevation 1000–2300 m (3300–7500 ft)
Distribution
from FNA
WA
[WildflowerSearch map]
[BONAP county map]
Discussion

Petrophytum hendersonii is known only from the Olympic Mountains of northwestern Washington.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 9, p. 412.
Parent taxa Rosaceae > subfam. Amygdaloideae > tribe Spiraeeae > Petrophytum
Sibling taxa
P. caespitosum, P. cinerascens
Synonyms Eriogynia hendersonii, Luetkea hendersonii, Spiraea hendersonii
Name authority (Canby) Rydberg: in N. L. Britton et al., N. Amer. Fl. 22: 253. (1908)
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