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BETULACEAE BIRCH FAMILY

John O. Sawyer, Jr.

Shrub, tree; monoecious. Stem: trunk < 35 m; bark smooth to scaly, peeling in thin layers or not, lenticels present or not. Leaf: simple, alternate, petioled, deciduous; stipules deciduous; blade ovate to elliptic, generally serrate, generally ± doubly so. Inflorescence: catkin, generally appearing before leaves, often clustered; bracts each subtending 2–3 flowers, 3–6 bractlets. Staminate inflorescence: pendent, ± elongate. Pistillate inflorescence: pendent or erect, developing variously in fruit (see key to genera). Staminate flower: sepals 0–4, minute; petals 0; stamens 1–10; pistil vestigial or 0. Pistillate flower: sepals 0–4; petals 0; stamens 0; pistil 1, ovary inferior or superior, chambers 2, each 1-ovuled by abortion, stigmas 2. Fruit: achene, nut, winged or not, subtended or enclosed by 1–2 bracts.
6 genera, 155 species: generally northern hemisphere; some cultivated. [Furlow 1997 FNANM 3:507–538] —Scientific Editor: Thomas J. Rosatti.

Key to Betulaceae

BETULA BIRCH
Stem: trunk < 30 m; bark smooth or scaly, aromatic, often peeling in thin layers; twigs puberulent, glandular, or both; lenticels prominent; winter buds sessile, 3-scaled. Leaf: glandular-hairy; blade 2–5 cm, wide-elliptic, base ± truncate to tapered. Staminate inflorescence: 2–7 cm; bracts each subtending 3 flowers, 3 bractlets. Pistillate inflorescence: 2–3 cm; bracts each subtending 3 flowers, 3 bractlets. Staminate flower: sepals 4; stamens 2. Pistillate flower: sepals 0. Fruit: many, in a non-cone-like catkin, not enclosed by bract, winged; bracts lobed, papery, released with but not attached to fruit.
50 species: circumboreal. (Latin: birch) Important wildlife food; wood used for interior finishing; many species cultivated.

Key to Betula

B. occidentalis Hook. WATER BIRCH
NATIVE
Stem: trunks to 10 m; bark red-brown to black, not peeling; twigs with large resin glands, hairy. Leaf: petiole < 15 mm, hairy; blade 2–5 cm, wide-ovate, glands especially adaxially, base ± truncate to tapered. Pistillate inflorescence: 3–5 cm; bract fringed with hairs.
Streamsides, springs; 600–2900 m. Klamath Ranges, High Cascade Range, High Sierra Nevada, Great Basin Floristic Province, Desert Mountains; scattered in western North America. Apr–May [Online Interchange]

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Nov 1 2014
Citation for this treatment: [Author of taxon treatment] 2013. Betula, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=15658, accessed on Nov 1 2014

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click for enlargement Betula occidentalis
See CalPhotos for additional images
Jo-Ann Ordano © 2000 California Academy of Sciences

Geographic subdivisions indicated for the distribution of Betula occidentalis Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.