Betula papyrifera |
Betula michauxii |
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paper birch |
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Habit | Trees to 20 m; bark white with dark lenticels, peeling off in papery sheets. | |
Twigs | ascending, glabrous or with scattered coarse hairs; resin-blisters few or none. |
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Leaves | blades usually narrowly ovate, sometimes ovate, 47–93 × 34–66 mm, green above; very pale green beneath; thin, bases broadly obtuse or rounded; seldom truncate; margins sharply toothed throughout; teeth mostly acuminate, irregular in size; largest teeth 1–2 mm; secondary veins 5–8 on each side; tips short-acuminate; surfaces glabrous except for spreading long hairs on midrib (at least in axils of secondary veins abaxially); petioles 17–30 mm, glabrous or with a few coarse hairs. |
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Fruits | broadly winged; wing at least as broad as seed. |
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Pistillate catkins | 25–28 mm; bracts with a long; narrow central lobe and short; broad lateral lobes. |
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Betula papyrifera |
Betula michauxii |
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Distribution | ||
Discussion | Riverbanks. Flowering Mar–May. 300–1100 m. BW. ID, WA, north to Yukon, east to Newfoundland. Native. In Oregon, paper birch is known only from a few sites along the Minam River in the Wallowa Mountains and one site on the Umatilla River in the northern Blue Mountains. Several ploidy levels have been reported from B. papyrifera (Li et al. 1996; Dugle 1966), but no chromosome counts are available from Oregon populations. |
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Source | Flora of Oregon, volume 2, page 383 Alan Whittemore |
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Sibling taxa | ||
Synonyms | Betula papyrifera var. commutata, Betula papyrifera var. subcordata | |
Web links |
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