Betula lenta is a tree to 25 m; roots of birches associated with ectomycorrhizal fungi, especially the Basidiomycete family Russulaceae (Bills et al. 1986; Smith and Read 1997); outer bark black, smooth dark when young, often shiny, rough with age, with thick loose edged plates, lenticels horizontal, twigs and inner bark sweetly aromatic, wintergreen odor when crushed; winter buds sharply pointed.
Leaves alternate, egg-shaped, to 10 cm long, tip pointed, base rounded to slightly lobed, margin very finely toothed; leaves expand mid-May; winter plant leafless 166 days (Britton 1874).
Flowers with sexes separate (monoecious), tiny, in catkins to 3 cm long, April, wind pollinated before leafing out.
Fruit: dry, tiny winged nuts, in enlarged catkin, ripen Aug.-Sept., wind dispersed, Sept.-Nov. Seeds &/or buds and catkins eaten by a few birds and small mammals. (Martin et al 1951).
Wetland status: FACU.
Frequency in New York City: Common.
Habitat: Moist to dry, upland, forests. It grows well on relatively acidic, gneiss-derived soils (Balter and Loeb 1983). Seedlings need partial shade, trees moderately shade tolerant, index 4-6; grows fast. Growth rate 4.75 (relative to 9.24 for B. populifolia and 0.99 for sugar maple). Growth rate was found to correlate well with relative intolerance to shade (Grime 1965). Needs well-drained acid soils, pH 3.6-6.8 (USDA, NRCS 2010). Resistant to ozone Moderately tolerant of salt and drought. Sensitive to sulfur dioxide and soil compaction (Hightshoe 1988; Baker 1945).
Notes: Twigs eaten by deer & rabbits (Martin et al 1951). Black birch is quite susceptible to Nectria canker (Nectria galligena, Ascomycotina, Pyrenomycetes) with red, bead-like fruiting bodies. This fungus causes cankers that begin as small dark depressed areas on young bark. As the canker progresses it develops a target-like appearance as successive layers of callus tissue are killed and die back. Eventually it girdles and kills branches. White trunk rot, of black birch is caused by Phellinus igniarius, (Basidiomycotina). The fruiting body of this is a woody brown or gray bracket fungus called the flecked-flesh polypore. Brown wood rot of black birch is caused by Pholiota limonella, (Basidiomycotina, Hymenomycetes). The fruiting body of this fungus is the yellow cap fungus, a yellow, slimy, scaly-capped mushroom that grows in clusters on infected wood (Sinclair et al. 1987; Agrios 1988; Lincoff 1981). Black birch is also attacked by the larvae of the dusky birch sawfly, Croesus latitarsus (Hymenoptera: Symphyta). These feed on leaves, generally in groups. The mature larvae has a shiny black head and yellow-green body with rows of large black spots. Black birch is also attacked by gypsy moths, Lymantria dispar; the birch tubemaker, Acrobasis betulella, the larvae of this moth is about 2 cm long with a dark purplish body. It binds unfolding leaves together with silk and fecal pellets and skeletonizes the leaves. The birch skeletonizer, Bucculatrix canadensisella, (Lepidoptera, Lyonetiidae), has a small larva that eats soft leaf tissues leaving a transparent, vascular skeleton behind. Larvae of the luna moth, Actias luna; promethea moth, Callosamia promethea; polyphemus moth, Antheraea polyphemus; imperial moth, Eacles imperialis; four-horned sphinx moth, Ceratomia amyntor; small-eyed sphinx moth, Paonias myops; white-marked tussock moth, Orgyia leucostigma; Virginia tiger moth, Spilosoma virginica; tiger swallowtail butterfly, Papilio gaucus; mourning cloak butterfly, Nymphalis antiopa; also eat birch (Opler 1992; Tallamy 2003). Black birch is easily killed by fire (Burns & Honkala 1990; Hightshoe 1988; Johnson and Lyon 1991; Borror and White 1970).