The Color of Birch

Flowers

• Birch flowers are either male or female catkins, elongated flower clusters. Emerging before the leaves, they may be light or dark brown if they are male and pale green if they are female, like those of the paper birch (Betula papyrifera), hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 2 through 6 or 7 and the river or red birch (Betula nigra), hardy in USDA zones 3b through 9. Although individual catkins are never more than a few inches long, they cover the tree, providing color.

Bark

• Paper birch is a variety with exfoliating bark. Its young branches feature reddish brown bark that becomes smooth and white on branches and the trunk as the plant matures. The white bark peels and reveals orange-red bark underneath. Older paper birches feature black spots on their white outer bark. A young sweet or cherry birch (Betula lenta), hardy in USDA zones 3 through 7, features dark, reddish brown bark that turns brown-black as the tree ages. Silver birch (Betula pendula), hardy in USDA zones 2 through 6 or 7, features non-exfoliating white bark that turns mostly black with age.

Leaves

• Most birch species' leaves turn one or another shade of yellow in fall. Yellow birch (Betula alleghaniensis), hardy in USDA zones 3 through 7, features leaves that are green on top and lighter, greenish yellow on the underside in late spring and summer. In fall, the leaves turn golden yellow. Paper birch and sweet birch have either shiny or matte green leaves in summer, but they turn brilliant yellow in fall. Sweet birch has the best fall color among popular birch species, according to Michael A. Dirr, professor emeritus at the University of Georgia, in his book "Manual of Woody Landscape Plants."

Culture for Color

• Maximize the color of birch flowers, foliage and bark by planting a birch in a sunny to partly shady site with ample soil moisture. Those conditions are especially critical to the production of yellow fall leaf color and the retention of the leaves during fall. Applying mulch on top of the soil helps to retain soil moisture, but do not allow mulch to touch the birch tree's or shrub's trunk because that arrangement promotes the spread of bacteria and fungal diseases. Birches often are grouped for their optimal landscape effect.