OregonFlora: Betula lenta vs. Betula glandulosa

	Betula lenta	Betula glandulosa
		resin birch
Habit		Shrubs to 3 m; bark dark brown with pale lenticels, dull, not exfoliating.
Twigs		ascending, glabrous or puberulent with spreading hairs to 0.1 mm; dry or rarely glutinous near apex, with few to many resin-blisters.
Leaves		blades elliptic to almost circular, 15–28 × 12–21 mm (on fertile branches; up to 37 × 31 mm on sterile branches), green above, light green beneath; firm but flexible, bases obtuse or rounded (seldom broadly acute); margins crenate; crenations obtuse or rounded, 8–15 on a side, usually all approximately same size; ~1 mm; secondary veins 3–4(5) on each side; tips broadly rounded; surfaces abaxially glabrous or both sides vernicose; petioles 3–7 mm, glabrous.
Fruits		narrowly winged.
Pistillate catkins		15–24 mm; bracts with a long; narrow central lobe and short; broad lateral lobes.

	Betula lenta	Betula glandulosa
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion		Wet meadows, bottomlands, swamps, streambanks. Flowering May–Jul. 300–2200 m. BR, BW, Casc, ECas, Lava. CA, ID, WA; north to AK, east to Greenland. Native. Betula glandulosa and B. pumila are morphologically similar and difficult to distinguish. Elsewhere in North America, B. glandulosa is diploid and B. pumila is tetraploid, but no chromosome counts have been made from the Pacific Slope populations. Dugle (1966) has reported B. glandulosa × B. pumila (B. × sargentii) and B. glandulosa × B. occidentalis (B. × eastwoodiae) from other parts of western North America, but neither hybrid has been confirmed from Oregon.
Source		Flora of Oregon, volume 2, page 382 Alan Whittemore
Sibling taxa	B. glandulosa, B. occidentalis, B. papyrifera, B. pendula, B. pumila	B. occidentalis, B. papyrifera, B. pendula, B. pumila
Synonyms		Betula glandulosa var. glandulosa
Web links	WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Betula lenta

Betula glandulosa

resin birch

Habit

Shrubs to 3 m; bark dark brown with pale lenticels, dull, not exfoliating.

Twigs

ascending, glabrous or puberulent with spreading hairs to 0.1 mm; dry or rarely glutinous near apex, with few to many resin-blisters.

Leaves

blades elliptic to almost circular, 15–28 × 12–21 mm (on fertile branches; up to 37 × 31 mm on sterile branches), green above, light green beneath; firm but flexible, bases obtuse or rounded (seldom broadly acute);

margins crenate; crenations obtuse or rounded, 8–15 on a side, usually all approximately same size; ~1 mm;

secondary veins 3–4(5) on each side;

tips broadly rounded;

surfaces abaxially glabrous or both sides vernicose;

petioles 3–7 mm, glabrous.

Fruits

narrowly winged.

Pistillate catkins

15–24 mm;

bracts with a long; narrow central lobe and short; broad lateral lobes.

Betula lenta

Betula glandulosa

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Wet meadows, bottomlands, swamps, streambanks. Flowering May–Jul. 300–2200 m. BR, BW, Casc, ECas, Lava. CA, ID, WA; north to AK, east to Greenland. Native.

Betula glandulosa and B. pumila are morphologically similar and difficult to distinguish. Elsewhere in North America, B. glandulosa is diploid and B. pumila is tetraploid, but no chromosome counts have been made from the Pacific Slope populations. Dugle (1966) has reported B. glandulosa × B. pumila (B. × sargentii) and B. glandulosa × B. occidentalis (B. × eastwoodiae) from other parts of western North America, but neither hybrid has been confirmed from Oregon.