The Long Island Dahlia Society will hold a dahlia basic class about different methods of successfully wintering over dahlia tubers on Thurs., Nov. 20, 7 p.m. in the Carriage House at the Bayard Cutting Arboretum on Montauk Highway in East Islip. For information, visit www.LongIslandDahlia.com or call Joe at 631-754-1002 in the evening or 516-832- 3652 during the day.