Fact Sheet No. 201, UMaine Extension No. 5030 Prepared by James Dill, Frank Drummond, and David Yarborough, The University of Maine, Orono, ME 04469. All photographs taken by James Dill.  Original prepared by J. Dill, H. W. Forsythe and A. A. Ismail in 1982 as Cooperative Extension Service Fact Sheet No. 201. Revised February 2001.