color and may be somewhat hairy when young. The flowers are wind-pollinated catkins; the female flowers are greenish and long growing from the tips of twigs. The male (staminate) flowers are long and a brownish color. The tree flowers from mid-April to June depending on location. Paper birch is monoecious, meaning that one plant has both male and female flowers. The fruit matures in the fall. The mature fruit is composed of numerous tiny winged seeds packed between the catkin bracts. They drop between September and spring. At 15 years of age, the tree will start producing seeds but will be in peak seed production between 40 and 70 years. The seed production is irregular, with a heavy seed crop produced typically every other year and with at least some seeds being produced every year. In average seed years, are produced, but in bumper years may be produced. The seeds are light and blow in the wind to new areas; they also may blow along the surface of snow. The roots are generally shallow and occupy the upper of the soil and do not form taproots. High winds are more likely to break the trunk than to uproot the tree. Genetics and taxonomy B. papyrifera hybridizes with other species within the genus Betula. Several varieties are recognized: B. p. var papyrifera the typical paper birch B. p. var cordifolia the eastern paper birch (now a separate species); see Betula cordifolia B. p. var kenaica Alaskan paper birch (also treated as a separate species by some authors); see Betula kenaica B. p. var subcordata Northwestern paper birch B. p. var. neoalaskana Alaska paper birch (although this is often treated as a separate species); see Betula neoalaskana Distribution Betula papyrifera is mostly confined to Canada and the far northern United States. It is found in interior (var. humilus) and south-central (var. kenaica) Alaska and in all provinces and territories of Canada, except Nunavut, as well as the far northern continental United States. Isolated patches are found as far south as the Hudson Valley of New York and Pennsylvania, northern Connecticut, and Washington. High elevation stands are also in mountains to North Carolina, New Mexico, and Colorado. The most southerly stand in the Western United States is located in Long Canyon in the City of Boulder Open Space and Mountain Parks. This is an isolated Pleistocene relict that most likely reflects the southern