Photo: Doug McGrady from Warwick, RI, USA, CC BY 2.0 · Wikimedia Commons
Sweet Birch (Black Birch)
Betula lenta
Also called black birch, cherry birch, mahogany birch.
Wintergreen-scented twigs, tight cherry-like black bark that never peels and clear gold fall color on the birch that feeds 284 kinds of caterpillars.
Wildlife valueFall color
- Type
- Medium tree
- Mature height
- 40–70 ft
- USDA zones
- 3–8
- Growth rate
- Medium
- Sun
- Full · Part
- Soil moisture
- Average
210
Sweet birch is the dark-barked birch of the Appalachians, native from southern Maine and New York south through Pennsylvania, Maryland and the mountains to northern Georgia and Alabama, on cool north and east slopes and rocky ridges. Snap a twig and it smells of wintergreen; this tree was once the only source of oil of wintergreen, and its sap made birch beer. The bark is smooth, reddish black and ringed with horizontal lenticels like a cherry, and it does not peel; the leaves turn clear gold in fall. Birch is a keystone genus, host to 284 kinds of caterpillars, the mourning cloak, tiger swallowtail, green comma, polyphemus and cecropia among them, and the winged seed feeds redpolls, siskins and goldfinches through winter while grouse eat the buds. Ideal for a north or east slope, the edge of a woodlot or a lawn with room, where it takes the birch slot that river birch usually gets.
It is seldom sold because river birch fills that slot at garden centers, yet in the hills of Pennsylvania and Maryland it is the birch that belongs, and it is reported to resist the bronze birch borer. Male catkins hang on the twig tips all winter and open in April; the female cones shatter in fall. It wants a cool, uncompacted site: on a hot lawn in the coastal plain it sulks, and a stressed tree is prone to Nectria canker. Old trees break into dark plates and live past 200 years.
How to grow Sweet Birch
Sweet birch is hardy in zones 3 through 8 and grows in full sun or part shade in moist, acid, well-drained soil; it takes rocky or thin ground but not compacted soil or a hot paved strip, and likes a cool north or east slope. Expect 40 to 70 feet tall and 35 to 40 feet wide, so plant it 25 feet from the house.
Plant a dormant bare-root or potted sapling from leaf fall until bud swell, in a hole wider than the roots and no deeper, flare at the soil line, native soil back in and mulch kept off the trunk. The seed needs light: gather the cones in September as they turn brown, and sow the seed on the surface of a flat of moist mix, barely covered, left outdoors for the winter, or in spring after 4 to 8 weeks in a damp bag in the refrigerator. It comes up over 4 to 6 weeks and wants light shade its first summer.
Water weekly the first two summers when rain is short. Deer mostly leave birch alone, but bucks rub smooth young trunks in fall and rabbits and voles gnaw thin bark under snow, so cage it for three winters and keep the mulch thin at the stem. Prune in summer or after leaf fall; a birch cut in spring bleeds sap.
Growth is moderate to fast once it settles in, 46 feet at 20 years in Pennsylvania and West Virginia forests, and the first catkins come at 10 to 15 years. Male and female catkins share a tree and the wind carries the pollen. Leaf miners and skeletonizers mark the leaves some years. A sunken dead patch of bark on the trunk is Nectria canker, which sweet birch gets more readily than most trees; cut out cankered limbs.
Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.
- Multistem or single stem? Sometimes the trunk is hiding the answer
- Leaf litter, not wood chips, under the canopy
- Native trees and shrubs for butterflies and moths: host plants first, nectar second
- Native trees and shrubs for wildlife: what deer, squirrels, bears, bats, turtles and salamanders actually get from a planting
- Ten planting mistakes that quietly kill trees
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