Betula pubescens subsp. tortuosa

(Ledebour) Nyman

Consp. Fl. Eur., 672. 1881.

Basionym: Betula tortuosa Ledebour Fl. Ross. 3: 652. 1851
Synonyms: Betula odorata Bechstein
Treatment appears in FNA Volume 3.

Shrubs, 1–12 m; trunks usually many, often interlacing, branches ascending. Twigs with numerous small resinous glands. Leaf-blade ovate, rhombic-ovate, or suborbiculate-rhombic, 1–2.5 (–3.5) × 1–2 (–3) cm, base cuneate to truncate, margins coarsely serrate or dentate, apex acute; surfaces abaxially moderately pubescent. Infructescences 1–1.5 (–2) × 0.4–0.8 cm; scales pubescent to glabrous, often ciliate, central lobe oblong or narrowly triangular, apex acute to obtuse, lateral lobes divergent and ascending, about equal in length but somewhat broader. Samaras with wings about equal in diameter to body, broadest near summit, usually extended beyond body apically. 2n = 56.


Phenology: Flowering late spring.
Habitat: Protected inland valleys
Elevation: 0–200 m

Discussion

Betula pubescens subsp. tortuosa, which also occurs in Iceland, the mountains of Scandinavia, and arctic Europe, is native to southwestern Greenland; it has also been reported as well from Baffin Island, although I have not seen specimens. Based on pollen analyses (B. Fredskild 1991), this subspecies arrived in Greenland from Europe ca. 3500 years ago. Hybridization of this taxon with other birches in Greenland, Iceland, and Scandinavia has been studied by M. Sulkinoja (1990).

Selected References

None.

Lower Taxa

None.

"equal" is not a number."broader" is not a number."broadest" is not a number."equal" is not a number.

Acute (?) +  and Obtuse (?) +
John J. Furlow +
(Ledebour) Nyman +
tanniferous +  and furrowed +
light reddish-brown +  and tan or brownish or grayish white +
exfoliating +
cuneate to truncate +
Betula tortuosa +
2 (?) +  and 3 (?) +
slender +
staminate +  and pistillate +
solitary +  and in small racemose clusters +
ovoid +  and cylindric +
expanding +
triangular +  and oblong +
multibracteate +
Native +, Greenland +  and Europe +
0–200 m +
pistillate +  and staminate +
expanding +
subpendulous +  and pendulous +
cylindric +
Protected inland valleys +
1.5 cm15 mm <br />0.015 m <br /> (2 cm20 mm <br />0.02 m <br />) +
1 cm10 mm <br />0.01 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
1 cm10 mm <br />0.01 m <br /> (4 cm40 mm <br />0.04 m <br />) +
0.4 cm4 mm <br />0.004 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
membranaceous +
2.5 cm25 mm <br />0.025 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +
2 cm20 mm <br />0.02 m <br /> (3 cm30 mm <br />0.03 m <br />) +
1 cm10 mm <br />0.01 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
1 cm10 mm <br />0.01 m <br /> (2 cm20 mm <br />0.02 m <br />) +
dentate +  and serrate +
not obvious +  and defined +
membranaceous +
Flowering late spring. +
2(-3)-carpellate +
Consp. Fl. Eur., +
1-seeded +  and 2-winged +
extended +
crowded +  and imbricate +
deciduous +
pubescent +  and glabrous +
(1-)3-lobed +
expanding +
not woody +  and leathery +
paper-thin +
2 (?) +  and 3 (?) +
nearly +  and distinct +
Betula odorata +
Betula pubescens subsp. tortuosa +
Betula pubescens +
subspecies +
excurrent +  and branching +
interlacing +
differentiated +
tanniferous +
light +, nearly white +  and reddish-brown +
soft +  and hard +