Purshia (bitterbrush or cliff-rose) is a small genus of 5-8 species of flowering plants in the family Rosaceae, native to western North America, where they grow in dry climates from southeast British Columbia in Canada south throughout the western United States to northern Mexico. The classification of Purshia within the Rosaceae has been unclear.[1][2] The genus was originally placed in the subfamily Rosoideae, but is now placed in subfamily Dryadoideae.[3]

Purshia stansburiana 2.jpg
Purshia stansburyana
Scientific classification e
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Rosales
Family: Rosaceae
Subfamily: Dryadoideae
Genus: Purshia
DC. ex Poir.
Type species
Purshia tridentata

See text

Purshia distribution.svg

They are deciduous or evergreen shrubs, typically reaching 0.3–5 m tall. The leaves are small, 1–3 cm long, deeply three- to five-lobed, with revolute margins. The flowers are 1–2 cm diameter, with five white to pale yellow or pink petals and yellow stamens. The fruit is a cluster of dry, slender, leathery achenes 2–6 cm long. The roots have root nodules that host the nitrogen-fixing bacterium Frankia.[4]

The evergreen species were treated separately in the genus Cowania in the past; this genus is still accepted by some botanists.



  1. ^ Morgan, D.R.; Soltis, D.E.; Robertson, K.R. (1994). "Systematic and evolutionary implications of rbcL sequence variation in Rosaceae". American Journal of Botany. 81 (7): 890–903. doi:10.1002/j.1537-2197.1994.tb15570.x. JSTOR 2445770.
  2. ^ Eriksson, T.; Hibbs, M.S.; Yoder, A.D.; Delwiche, C.F.; Donoghue, M.J. (2003). "The phylogeny of Rosoideae (Rosaceae) based on sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA and the trnL/F region of chloroplast DNA". International Journal of Plant Sciences. 164 (2): 197–211. doi:10.1086/346163.
  3. ^ Potter, D.; Eriksson, T.; Evans, R.C.; Oh, S.; Smedmark, J.E.E.; Morgan, D.R.; Kerr, M.; Robertson, K.R.; Arsenault, M.; Dickinson, T.A.; Campbell, C.S. (2007). "Phylogeny and classification of Rosaceae". Plant Systematics and Evolution. 266 (1–2): 5–43. doi:10.1007/s00606-007-0539-9.
  4. ^ Swensen, S.M.; Mullin, B.C. (1997). "The impact of molecular systematics on hypotheses for the evolution of root nodule symbioses and implications for expanding symbioses to new host plant genera". Plant and Soil. 194 (1–2): 185–192. doi:10.1023/A:1004240004063.

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