Grey Birch Seeds: How Do They Get Spread?

Identification

• Though many of the birches (Betula spp.) are noted for their attractively exfoliating bark, which comes off in large, curling sheets, the grey birch’s bark does not peel. Its landscape appeal stems from its shiny, dark-green leaves and bark, not from its insignificant flowers or its relatively uninteresting form. It is intolerant of heat, which means it grows best in areas where summer temperatures stay below 75 degrees Fahrenheit. It prefers well-drained, drier soils in full sun or part shade, and grows to heights of 20 to 40 feet under ideal conditions.

Flowering and Fruiting

• The grey birch is monoecious, which means it produces both male and female flowers on the same tree rather than producing two different trees, one for each sex. Upright 3/4-inch male catkins grow near the end of the twig, while female catkins are about 1/2 inch long. Male flowers are preformed and elongate in spring, while female blossoms appear early in the growing season. Because the tree has both sexes on the same structure, it will form seeds every year. Pollinated female flowers mature to large cone-like structures that are roughly 3/4-inch long at maturity.

Seed Dispersal

• The grey birch’s mature cones each contain a large complement of winged nutlets. Unlike the distinctive samaras or helicopters of some trees, grey birch’s small seed is embedded in a paper substance which extends to either side. The cones mature by late summer or early autumn, and the seeds slowly disperse over the late fall and winter, falling from the cone and borne on wind across the landscape.

Grey Birch Reproduction

• In addition to freely self-seeding under optimum conditions, grey birch often suckers, meaning it puts up new shoots from its root structures. If left to its own devices, grey birch can form attractive stands or thickets. If you do not wish to cultivate a miniature birch forest on your property, you will need to manage seedlings and suckers. Both can be lopped below the soil line using a sharp pair of shears or mowed when they are still small enough, before the wood hardens.