BETULACEAE (Birch Family)

Contributed by Alan Whittemore

Plants trees or shrubs, monoecious. Leaves alternate, short- to less commonly long-petiolate. Leaf blades simple, pinnately veined, the margins toothed. Stipules scarious or somewhat hardened, broadly ovate, mostly shed during leaf development. Inflorescences of separate staminate and pistillate catkins (the pistillate ones in globose clusters in Corylus). Flowers actinomorphic, imperfect. Staminate flowers with calyces absent or of (1–)4(–6) minute, scalelike sepals; corollas absent; stamens mostly 4–6, with a reduced, nonfunctional pistil sometimes present. Pistillate flowers with calyces rudimentary or absent; corollas absent; stamens and staminodes absent; ovary inferior (but often appearing naked in the absence of perianth), with 2 locules toward the base but often appearing 1-locular toward the tip, the placentation axile. Styles 2 (sometimes united basally), each with a linear stigmatic region toward the tip. Fruits nuts, nutlets, or samaras, surrounded by bracts and often grouped into conelike infructescences. Six genera, 125–150 species, North America to South America, Europe, Asia.

Species of Betulaceae form an important part of the woody vegetation in many parts of Missouri. Many Betulaceae are tolerant of flooding and waterlogging, and they are a common component of the woody cover on stream banks and wet bottomlands. Other species dominate the woody understory in some Missouri forests. The seeds of all of our species are eaten by birds and other wildlife.