Home/Species/ Henderson's Rockmat

Petrophytum hendersonii

(Canby) Rydb.

Henderson's Rockmat

G3Vulnerable Found in 4 roadless areas NatureServe Explorer →

G3VulnerableGlobal Rank

LowThreat Impact

Identity

Unique IDELEMENT_GLOBAL.2.161457

Element CodePDROS18040

Record TypeSPECIES

ClassificationSpecies

Classification StatusStandard

Name CategoryVascular Plant

Endemicendemic to a single state or province

KingdomPlantae

PhylumAnthophyta

ClassDicotyledoneae

OrderRosales

FamilyRosaceae

GenusPetrophytum

Synonyms

Petrophyton hendersonii(Canby) Rydb.

Other Common Names

Olympic Mountain rockmat (EN) Olympic Mountain Rockmat (EN)

Concept Reference

Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

Conservation Status

Rank Method Rank calculation - Biotics v2

Review Date2024-04-15

Change Date1988-05-16

Edition Date2000-07-27

Edition AuthorsMacBryde, B. (2000), rev. Eberly and Wessel (2024)

Threat ImpactLow

Range Extent1000-5000 square km (about 400-2000 square miles)

Number of Occurrences6 - 20

Rank Reasons

Petrophyton hendersonii is a shrub that of the western United States that is endemic to the Olympic Mountains. While there are only around 12 occurrences, they are largely on National Park Service lands where threats are low.

Range Extent Comments

Petrophytum hendersonii occurs in the western United States where it is endemic to the Olympic Mountains of northwestern Washington.

Threat Impact Comments

This species is threatened by recreation, competitive invasive plant species, and herbivory by introduced mountain goats (Crawford et al. 2009). Occurrences of this species are largely on National Park Service lands which provides protection against many threats including development and roads. It is expected to be more resilient to projected effects of climate change in the Olympic alpine in comparison to other taxa that are more restrictive in their habitat associations (Wershow & Dechaine 2018). There is a potential minor threat of collection for horticultural trade and propagation in rock gardens.

Ecology & Habitat

Habitat

This species grows on outcrops, cliffs, and, talus slopes at elevations of 1,000 to 2,300 m (FNA 2014).

Terrestrial Habitats

Bare rock/talus/screeCliff

Other Nations (1)

United StatesN3

Province	Rank	Native
Washington	S3	Yes

Threat Assessments

Threat	Scope	Severity	Timing
5 - Biological resource use	Unknown	Unknown	High (continuing)
5.2 - Gathering terrestrial plants	Unknown	Unknown	High (continuing)
5.2.1 - Intentional use (species being assessed is the target)	Unknown	Unknown	High (continuing)
6 - Human intrusions & disturbance	Restricted - small	Moderate - slight	High (continuing)
6.1 - Recreational activities	Restricted - small	Moderate - slight	High (continuing)
8 - Invasive & other problematic species, genes & diseases	Large (31-70%)	Unknown	High (continuing)
8.1 - Invasive non-native/alien species/diseases	Restricted (11-30%)	Moderate or 11-30% pop. decline	High (continuing)
8.1.1 - Unspecified species	Restricted (11-30%)	Moderate or 11-30% pop. decline	High (continuing)
8.2 - Problematic native species/diseases	Large (31-70%)	Unknown	High (continuing)
8.2.2 - Named species	Large (31-70%)	Unknown	High (continuing)
11 - Climate change & severe weather	Pervasive (71-100%)	Slight or 1-10% pop. decline	High - low
11.1 - Habitat shifting & alteration	Pervasive (71-100%)	Slight or 1-10% pop. decline	High - low

Plant Characteristics

DurationPERENNIAL

Economic Value (Genus)No

Roadless Areas (4)

Washington (4)

Area	Forest	Acres
Jefferson Ridge	Olympic National Forest	6,512
Lightning	Olympic National Forest	7,179
South Quinault	Olympic National Forest	11,081
Upper Skokomish	Olympic National Forest	9,311

References (11)

Abrams, L. 1944. Illustrated flora of the Pacific states: Washington, Oregon, and California. Vol. 2. Polygonaceae to Krameriaceae. Stanford Univ. Press, Stanford, California. 635 pp.
Crawford, R.C., C.B. Chappell, C.C. Thompson, and F.J. Rocchio. 2009. Vegetation classification of Mount Rainier, North Cascades, and Olympic national parks. Plant association descriptions and identification keys: Appendices A-G. Natural Resource Technical Report NPS/NCCN/NRTR--2009/D-586. National Park Service, Fort Collins, CO. 586 pp.
Flora of North America Editorial Committee (FNA). 2014b. Flora of North America north of Mexico. Vol. 9. Magnoliophyta: Picramniaceae to Rosaceae. Oxford University Press, New York. xxiv + 713 pp.
Hitchcock, C.L., A. Cronquist, M. Ownbey, and J.W. Thompson. 1961b. Vascular plants of the Pacific Northwest. Part 3: Saxifragaceae to Ericaceae, by C.L. Hitchcock and A. Cronquist. Univ. Washington Press, Seattle. 614 pp.
Hitchcock, C.L., and A. Cronquist. 1974. Flora of the Pacific Northwest: An illustrated manual. 2nd printing, with corrections. Univ. Washington Press, Seattle. xix + 730 pp.
International Plant Names Index (IPNI). 2012. Online. Available: http://www.ipni.org. (Accessed 2012).
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Washington Natural Heritage Program. 1981. An illustrated guide to the endangered, threatened and sensitive vascular plants of Washington. Washington Natural Heritage Program, Olympia. 328 pp.
Washington Natural Heritage Program. 1997. Endangered, Threatened and Sensitive Vascular Plants of Washington - with Working Lists of Rare Non-Vascular Species. Department of Natural Resources. Olympia. 62 p.
Washington Natural Heritage Program (WNHP). 2024. Online Field Guide to the Rare Plants of Washington. Online. Available: https://fieldguide.mt.gov/wa (accessed 2024).
Wershow, S. T. and E. G. DeChaine. 2018. Retreat to refugia: Severe habitat contraction projected for endemic alpine plants of the Olympic Peninsula. American Journal of Botany 105(4):760-778.

Petrophytum hendersonii

Habitat

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