Betula nigra (River Birch)
|Also known as:|
|Life cycle:||perennial woody|
|Habitat:||part shade, shade, sun; moist; floodplain forest|
|Bloom season:||April - May|
|Plant height:||50 to 80 feet|
|Wetland Indicator Status:||GP: FACW MW: FACW NCNE: FACW|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Male and female flowers are borne separately on the same tree (monoecious), in clusters called catkins. Male catkins are in groups of 1 to 3 at tips of 1 year old twigs, pendulous in flower, 1½ to 3½ inches long, developing in fall as a slender spike of tightly appressed scales and opening up the following spring. Female catkins are erect and stout, cylindrical, 1/3 to ½ inch long from new, spur-like lateral twigs on the same branch as the males.
Leaves and bark:
Leaves are alternate and simple in 2s or 3s on short, spur-like lateral twigs, and singly on the new, elongating terminal branchlets. The blade is broadly lance-shaped to nearly diamond-shaped, widest towards the base, 2 to 4 inches long, 1¼ to 2¾ inches wide, pointed at the tip, wedge-shaped to obscurely angled at the base, on a ¼ to 1/3 inch hairy stalk. Edges are coarsely and deeply double-toothed, the upper surface dark green and sparsely hairy becoming smooth, the lower surface lighter green with hairs on veins and in vein axils.
Bark is light reddish brown to salmon pink to creamy colored, typically very papery-shaggy and peeling in layers on younger stems and branches, older bark becoming coarse with gray, scaly plates on the lower trunk. Trunks can reach 20 inches diameter at breast height (dbh), though more commonly 12 to 16 inches.
Naturally occurring only in the floodplain forest of the Mississippi River in southestern Minnesota, River Birch might not be so familiar to people if it wasn't used so extensively in urban landscape plantings. While our other four native birch species are restricted to the cooler northern temperate zone, River Birch's North American range extends all the way south the the Gulf of Mexico. This higher heat tolerance is one reason River Birch is not so susceptible to the bronze birch borer that is so lethal to our other species when planted in hotter and drier urban sites. The deeply salmon pink, often heavily exfoliating bark and deeply double toothed leaves with wedge-shaped bases easily distinguish this from other birches.
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- River Birch tree in a landscape planting
- River Birch in a Mississippi River floodplain
- trunk of old tree
- winter catkins
Photos courtesy Peter M. Dziuk taken in various urban landscapes and nursery production fields, and in Winona County.
Have you seen this plant in Minnesota, or have any other comments about it?