In celebration of the 100th anniversary of its founding in 1915, the American Dahlia Society will hold a special Centennial Show September 17 – 21 in Hempstead, New York.  Hosted by the Mid Island Dahlia Society, this event includes tours of the dahlia garden at Planting Fields Arboretum as well as tours of private gardens, dahlia competitions, and educational symposium.  Three speakers sponsored by the American Horticultural Society will present: Hanu Pappu, head of the Dahlia Research Project at Washington State University, Allan M. Armitage, and Keith Hammett, ornamental plant breeder from New Zealand.  Register at www.dahlia.org by August 1.