When Do Birch Trees Bloom?

Not every spring wildflower fits well into a bouquet. The slender birch tree offers both male and female flowers in the form of catkins. Birch pollen fertilizes female flowers about the time the birch leaves open.

The birch is a hardy pioneer tree, among the first to colonize a cleared or burned-out area. Its bark is papery and its leaves delicately toothed. Birches are monoecious: they carry both male and female flowers on the same branch.

Male flowers appear on birch trees at the end of summer as clusters of erect catkins. Initially about 2 inches long, the green catkins overwinter on the tree, growing longer in the springtime. When the male catkins "bloom," they turn purple and release pollen to fertilize female flowers.

Female birch flowers also pass the winter on the birch tree, but they are enclosed in buds. In late May or early June, they emerge from the scaly buds to "bloom" as short catkins. Female birch flowers are receptive shortly before nearby male flowers release pollen.