Page  97 ï~~2002 THE MICHIGAN BOTANIST 97 THE BIG TREES OF MICHIGAN 30. Betula pendula Roth European White Birch Kenneth M. Hiser & Elwood B. Ehrle Department of Biological Sciences Western Michigan University Kalamazoo, MI 49008 The largest known European White Birch tree in Michigan is located northwest of Traverse City in Leelenau County in the northwest portion of the Lower Peninsula. Description of the Species: The European White Birch is a member of the Birch family, Betulaceae. In Michigan, the family is represented by a number of large shrub and tree genera. Members of the Birch family are typically monoecious, producing catkins of unisexual flowers lacking petals. These appear before leaves are mature in spring, and are wind-pollinated. Voss (1985) distinguishes between two tribes within the family, Betuleae and Coryleae. The two tribes are most readily differentiated according to their fruit and inflorescence. The fruit of Betuleae is a samara, while that of Coryleae is a wingless nut. Betuleae produce elongate, cone-like inflorescences, while Coryleae bear shorter and raceme-like inflorescences. These and other features indicate that Betuleae are the more primitive tribe. Within the tribe Betuleae, Betula is characterized as having solitary pistillate catkins which disintegrate when ripe (those of Alnus are clustered and persistent) (Hora 1981). The bark of Betula is often papery and peeling, with horizontally elongated lenticels. The leaves are alternate, pinnately veined, and doubly serrate. The trees are monoecious, with male and female catkins borne separately on an individual tree. Male catkins form in the fall and overwinter, while female catkins emerge in spring (Barnes & Wagner 1981). The localities shown on Voss' map (Fig. 1) are specimens from trees that have escaped from cultivation or from trees persistent from cultivation, where a home may once have existed. The European White Birch may be identified at first sight by silvery-white bark and ascending branches with slender, drooping branchlets. Because of these two features, it is also known as the Silver or Weeping Birch. At closer inspection, the twigs are reddish and ovate to deltoid leaf blades are doubly serrated and attached to long, slender petioles. The wings of the samara are broader than its body. The leaves are alternately arranged and are borne singly on long shoots and in pairs on spur shoots (Barnes & Wagner 1981). Location of Michigan's Big Tree: From Traverse City, the tree can be located by taking M-22 north, through the intersection with M-72 West, to the traffic light at Cherry Bend Road. Turn left on Cherry Bend Road; the tree is located about 1% miles from the traffic light (about % mile past Breithaupt Road). The

Page  98 ï~~98 THE MICHIGAN BOTANIST Vol. 41 98 THE MICHIGAN BOTANIST Vol. 41 2 1 l. FIGURE 1. Documented distribution in Michigan and characteristics of the European White Birch. Map is from Voss (1985). The asterisk indicates the county where Michigan's Big Tree is located. Illustrations are from Brown (1938). 1. Twig showing pistillate and staminate aments x%. 2. Bract and bracteoles from staminate ament showing stamens, x7. 3. Staminate flowers with subtending bracts and sepals, x7. 4. Pistillate flowers with subtending bracts, x15. 5. Bract and bracteoles from staminate ament showing stamens, x 7. 6. Winged nutlet, x4. 7. Scale from fruiting strobilus, x4. 8. Twig with mature leaves and fruiting catkins, x%. 9. Winter twig, x%.

Page  99 ï~~2002 THE MICHIGAN BOTANIST 99 tree is easily visible from the road in the front yard of a yellow farmhouse at 9510 Cherry Bend Road. Description of Michigan's Big Tree: The trunk of the tree divides at just above 4.5 feet into four branches and a main trunk. The circumference of the largest of the four branches was measured at 117" (297 cm). The circumference of the main trunk at breast height is 158" (401 cm) [Diameter= 50" (128 cm)]. The crown has a spread of 71' (21.5 m), and has been pruned and trimmed considerably. The height of the tree was measured at 78' (23.75 m). INVITATION TO PARTICIPATE If you would like to join us in extending this series of articles by visiting and describing one or more of Michigan's Big Trees, please contact Elwood B. Ehrle for help with locations, specifications for taking measurements, and assistance with the manuscript. The Michigan Botanical Club encourages your involvement in this activity. Please remember to ask permission before entering private property. LITERATURE CITED Barnes, B.V., & W.H. Wagner, Jr. 1981. Michigan Trees. A Guide to the Trees of Michigan and the Great Lakes Region. University of Michigan Press, Ann Arbor. viii + 383 pp. Brown, H.P. 1938. Trees of Northeastern United States. Christopher Publishing House Boston, MA. 490 pp. Hora, B. 1981. The Oxford Encyclopedia of Trees of the World. Oxford University Press. Oxford, U.K. 288 pp. Voss E. G. 1985. Michigan Flora. Part II. Dicots. (Saururaceae-Cornaceae). Bulletin of the Cranbrook Institute of Science No. 59 and University of Michigan Herbarium. xix + 724 pp.