River Birch

(Betulaceae - Birch Family)

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• Form
  • large shade tree
  • maturing at about 60' tall by 40' wide
  • upright pyramidal to upright oval growth habit; single-trunked trees are the natural form and are commercially available, but River Birch is often sold in multi-trunked form with two to five trunks per tree
  • rapid growth rate

• Culture
  • full sun to partial sun
  • prefers moist, slightly acidic soils (alkaline soils sometimes result in leaf chlorosis due to iron deficiency), but performs well in either wet or dry soils that are acidic to neutral in soil pH
  • propagated primarily by rooted stem cuttings, but also by seed
  • Birch Family, being highly resistant to the Bronze Birch Borer and basically trouble-free of most of the diseases and pests which plague other Birches
  • abundantly available in ball and burlap form, and increasingly available in container form
  • pruning has a side-effect if performed in late Winter and throughout Spring, as sap will profusely bleed from the wounds (this will not harm the tree, however, if it is done); pruning is best accomplished for this reason in late Summer and throughout Autumn
  • River Birch is somewhat sensitive to being transplanted in Autumn, and care should be taken to amend the soil, fertilize, water thoroughly, mulch adequately, and avoid Winter salt spray, to enhance survival chances during the first Winter

• Foliage
  • alternate, ovate, doubly serrated, and slightly incised
  • medium to dark green uppersides, fluttering in the wind (as do all members of the Birch Family) to expose the silvery-colored undersides
  • fall color is chartreuse in poor years, but golden-yellow to yellow-brown in good years
  • alkaline soils may sometimes cause iron-poor chlorotic foliage (leaves are medium green to chartreuse with dark green leaf veins, instead of solid dark green by late Summer)

• Flowers
  • male catkins expand to 3" in length in April, with the female flowers being ornamentally inconspicuous

• Fruits
  • ornamentally insignificant, resembling immature catkins, opening and shedding small nutlet seeds in Spring

• Twigs
  • red-brown ultra-thin twigs transition into cinnamon-colored, heavily-lenticeled young branches, exfoliating as a gray-brown-light orange mixture on the species form, but exfoliating to a cream-light orange-lavender color on selected varieties

• Trunk
  • gray-brown to almost black bark is very scaly to platy on the trunks of the species form, but selected varieties have papery exfoliating patches of peach, gray, purple, and orange bark that is highly ornamental

• ID Summary
  • strongly exfoliating bark that has orange, gray, and lavendar colors, combined with a multitrunked form, is the ornamental highlight of this species and its various selections and cultivars; most other Birches have white or gray bark
  • other appealing features include the fluttering and subtlely bicolored ovate foliage, the highly symmetrical branching that yields an upright oval growth habit, and the branching structure that is composed of ultra-thin twigs that are nearly parallel to each other, but arranged in three dimensions, rather than a flattened two-dimensional branching pattern in a single plane

• Function
  • specimen, focal point, group planting, or shade tree (casts a light dappled shade in youth, but a solid medium shade with maturity)

• Texture
  • fine texture in foliage and when bare
  • open to average density in foliage but thick density when bare (on mature trees)

• Assets
  • not subject to infestation by the lethal Bronze Birch Borer, as are some Birches in many regions of the United States
  • rapid growth and establishment
  • wet or dry site adaptable
  • exfoliating flaky bark in various mixed shades of cream, orange, and lavender
  • bicolored Summer foliage that shimmers in the breeze
  • single trunk or multitrunked (clump) forms
  • very symmetrical branching
  • foliage casts a light to medium-density shade, depending upon the maturity of the tree
  • golden fall color in good years

• Liabilities
  • alkaline soils sometimes cause chlorotic foliage
  • a few surface roots occur with age

• Habitat
  • zones 4 to 9
  • native to the Eastern and Midwestern United States

• Alternates
  • trees for rapid shade (Acer x fremanii, Alnus glutinosa, Fraxinus americana, Fraxinus pennsylvanica, Gleditsia triacanthos inermis, Zelkova serrata, etc.)
  • trees for ornamental bark (Acer griseum, Betula papyrifera, Gymnocladus dioicus, Quercus bicolor, Zelkova serrata, etc.)
  • trees whose foliage flutters in the breeze (Betula species, Ginkgo biloba, Populus species, etc.) or is bicolored in the breeze (Acer rubrum, Acer saccharinum, Betula species, Magnolia virginiana, Quercus bicolor, etc.)

• Variants
  • Betula nigra 'Heritage' (also known as 'Cully') - the popular cultivar of choice, possessing great vigor, but primarily noted for its heavily exfoliating (peeling) branches in the 2" to 6" diameter range which yield a cream, salmon, orange, lavender, and gray combination of bark colors, making it an excellent Midwestern and Southern substitute in the United States for Paper Birch and other white-barked birches, the latter of which often develop heavy Bronze Birch Borer infestations with age, leading to apical branch dieback and tree death unless annual preventive spray programs are implemented. Heritage River Birch and other selections of this species are superior substitutes for the over-utilized shade tree known as Silver Maple (Acer saccharinum), since, in addition to its above-listed attributes, River Birch has wood that, although rapidly growing and relatively lightweight, is not brittle and therefore not prone to wind or ice damage, as is Silver Maple. River Birch is also much more symmetrically growing, has fewer and smaller surface roots, and does not have fruit litter problems, as does Silver Maple.

• Translation
  • Betula is the classical name for Birch.
  • nigra translates as "black", referring to the mature bark color of the wild species.

• Purpose
  • River Birch is one of the very best and most rapidly growing shade trees, that also has outstanding ornamental bark.

• Summary
  • Betula nigra is a large, rapidly-growing, fine-textured, highly symmetrical shade tree for dry or wet sites, with nursery-grown selections often sold in clumps of two to five trunks, having peach-colored exfoliating bark that is quite attractive, especially in Winter.