By John Parrish. First published by the National Park Service's National Capital Region Network in 2011, and online in 2024.
There is more to the nine native members of the birch family in the National Capital Region than white bark and canoes.
The birch family
Most trees and shrubs of the birch family (Betulaceae) are native to subarctic and cool temperate parts of the Northern Hemisphere. The family has six genera and about 150 species worldwide, seventeen of them native to the eastern United States.
- Flowers. Birches carry male and female flowers on the same plant. Long, pendulous male catkins hang conspicuously near the branch tips in winter and early spring, and wind carries their pollen to the smaller female flowers.
- Fruit. After pollination the flowers become nuts (Corylus), nutlets (Carpinus and Ostrya) or tiny winged samaras (Betula and Alnus) — important food for birds and small mammals.
- Uses. Most American-made toothpicks are birch wood; birch oil flavours food; hazelnuts go into nut butters and other foods; and the shock-resistant wood of hop hornbeam and ironwood makes tool handles, mallets and golf club heads.
The nine natives
| Species | Form and where | How to know it | Notes |
|---|---|---|---|
| Yellow birch (Betula alleghaniensis) | tree of the mountains; at Catoctin Mountain Park along streams and at high elevations | bronzy-yellow bark peeling in thin, flaky strips; twigs and inner bark faintly taste and smell of wintergreen | wood used for cabinets, flooring and toothpicks; likes cool climates, so its range will likely shrink with climate change — worth monitoring as a gauge of regional impacts |
| Black birch (Betula lenta) | tree, most plentiful in the mountains, uncommon in the Piedmont, absent from the Coastal Plain | dark bark like a cherry's | birch oil (methyl salicylate), also found in wintergreen, is distilled from its inner bark and twigs — the original flavouring of birch beer, also used in sweets; tapped in spring for birch syrup, like maple syrup |
| Gray birch (Betula populifolia) | a northeastern tree at the southern edge of its range, so extremely rare here; known along the fall line in the upper Anacostia watershed but in no park | grayish-white bark | a pioneer of forest edges, burned areas and disturbed sandy or gravelly ground; the Baltimore–Washington Parkway and Greenbelt Park have the best habitat for it |
| River birch (Betula nigra) | the region's most common birch; a multi-trunked tree, locally abundant on the Potomac's banks and along smaller streams, often leaning over water in floodplains | graceful, drooping small branches; chalky white to tan bark peeling from trunk and branches, becoming dark gray and scaly with age | a popular landscaping tree |
| Smooth alder (Alnus serrulata) | shrub, always near water — stream banks and swamps; widespread but uncommon | — | lives in partnership with nitrogen-fixing bacteria in its root nodules, trading carbon for nitrogen; alder thickets give birds nesting habitat, and many birds eat the seeds |
| Ironwood (Carpinus caroliniana), also American hornbeam, blue beech or musclewood | common understory tree of moist slopes and bottomlands | smooth, gray, fluted trunk and branches; usually leaning and well branched, with fine twigs | very hard, durable wood |
| American hazelnut (Corylus americana) | multi-stemmed shrub of rich, moist soil; widespread but uncommon | one of the earliest woody plants to flower, sometimes in late winter; male catkins up to four inches long; tiny magenta female flowers under two millimetres, best seen with a hand lens | edible nuts in a leafy husk by late summer — relished by wildlife, so you are unlikely to find any |
| Beaked hazelnut (Corylus cornuta) | shrub like the American hazelnut; rare, known here only at Catoctin Mountain Park and Harpers Ferry National Historical Park, in habitats from dry rocky woods to seepage swamps | husk tapered into a "beak" | edible nuts favoured by wildlife |
| Hop hornbeam (Ostrya virginiana), also called ironwood | uncommon small understory tree of rocky ground in the Piedmont and mountains | mature bark shaggy, flaking in short vertical strips, unlike the smooth, cherry-like bark of young branches | very hard, durable wood |
Relatives just outside the region
- Speckled alder (Alnus rugosa) and paper birch (Betula papyrifera) are the only birch-family natives of the Potomac watershed not found in the region. Both grow at high elevations on the Appalachian Plateau to the west. Speckled alder might just turn up at Catoctin Mountain Park or the far western C&O Canal National Historical Park; paper birch, which prefers cooler northern climates, almost certainly will not.
- Seaside alder (Alnus maritima) grows on Maryland's Eastern Shore, and green alder (Alnus viridis) to the north in south-central Pennsylvania.
The National Capital Region Network's Inventory and Monitoring programme tracks trees such as these as part of its forest vegetation monitoring.
Sources
- John Parrish, "Birch Family Natives of the National Capital Region," National Park Service, National Capital Region Inventory and Monitoring Network. https://www.nps.gov/articles/000/birches-of-the-ncr.htm
- The photographs, licensed from North Carolina State University's collection, Purdue Arboretum and the University of Minnesota, are not reproduced.
- Rewritten in hubnx's own words.
In these publicationsChesapeake & Ohio Canal National Historical ParkAntietam National BattlefieldCatoctin Mountain ParkGeorge Washington Memorial ParkwayHarpers Ferry National Historical ParkManassas National Battlefield Park
LanguagesEnglish
Licence: CC0 1.0 (public domain) · Adapted from www.nps.gov
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