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Betula occidentalis

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Betula occidentalis

Secure  (NatureServe)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fagales
Family: Betulaceae
Genus: Betula
Subgenus: Betula subg. Betula
B. occidentalis
Binomial name
Betula occidentalis
Natural range of Betula occidentalis
  • B. fontinalis Sarg.

Betula occidentalis, the water birch or red birch, is a species of birch native to western North America, in Canada from Yukon east to Northwestern Ontario and southwards, and in the United States from eastern Washington east to western North Dakota,[citation needed] and south to eastern California, northern Arizona and northern New Mexico, and southwestern Alaska. It typically occurs along streams in mountainous regions,[1] sometimes at elevations of 2,100 metres (6,900 feet) and in drier areas than paper birch.[2]

Trunk from along the Columbia River in Chelan County, Washington

It is a deciduous shrub or small tree growing to 14 m (46 ft) high, up to 25 centimetres (10 inches) thick.[2] It tends toward epicormic growth, with many small limbs sprouting from the trunk and causing the wood to be full of small knots. The bark is dark red-brown to blackish,[2] and smooth but not exfoliating. The twigs are glabrous or thinly hairy, and odorless when scraped. The leaves are alternate, ovate to rhombic, 1–7 cm (122+34 in) long and 1–4.5 cm (121+34 in) broad, with a serrated margin and two to six pairs of veins, and a short petiole up to 1.5 cm (12 in) long. The flowers are wind-pollinated catkins 2–4 cm (341+12 in) long, the male catkins pendulous, the female catkins erect. The fruit is 2–3 cm (341+14 in) long and 8–15 millimetres (1412 in) broad, composed of numerous tiny winged seeds packed between the catkin bracts.[1][3][4]

The identity of similar birches in Alaska is disputed; some include them in B. occidentalis, while others regard them as hybrids between Betula neoalaskana and Betula glandulosa.[1] A 2023 study sequenced chloroplast genomes of species from the genus Betula for phylogenetic analysis. Of the Betula species, B. occidentalis was most closely related to B. pendula purple rain and B. platyphylla.[5]

The foliage is browsed by sheep, goats,[6] and birds; some small birds also consume the seeds.[2]

Some Plateau Indian tribes used water birch to treat pimples and sores.[7]

It is also a riverside tree found in western USA that reacts to water stress by becoming isohydric.[8]


  1. ^ a b c Flora of North America: Betula occidentalis
  2. ^ a b c d Arno, Stephen F.; Hammerly, Ramona P. (2020) [1977]. Northwest Trees: Identifying & Understanding the Region's Native Trees (field guide ed.). Seattle: Mountaineers Books. pp. 215–220. ISBN 978-1-68051-329-5. OCLC 1141235469.
  3. ^ Plants of British Columbia: Betula occidentalis Archived 2017-12-06 at the Wayback Machine
  4. ^ Jepson Flora: Betula occidentalis
  5. ^ Zhang, M.; Gao, Y.; Su, X.; Liu, W.; Guo, Y.; Jiang, J.; Ma, W. (2023). "Access Electronic Resources". Mitochondrial DNA. Part B, Resources. 8 (2): 281–284. doi:10.1080/23802359.2023.2176182. PMC 9946319. PMID 36845004.
  6. ^ Little, Elbert L. (1980). The Audubon Society Field Guide to North American Trees: Eastern Region. New York: Knopf. p. 368. ISBN 0-394-50760-6.
  7. ^ Hunn, Eugene S. (1990). Nch'i-Wana, "The Big River": Mid-Columbia Indians and Their Land. University of Washington Press. p. 352. ISBN 0-295-97119-3.
  8. ^ Saliendra, Nicanor Z.; Sperry, John S.; Comstock, Jonathan P. (1995-05-01). "Influence of leaf water status on stomatal response to humidity, hydraulic conductance, and soil drought in Betula occidentalis". Planta. 196 (2): 357–366. doi:10.1007/BF00201396. ISSN 1432-2048. S2CID 40158479.

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