Once limited to a handful of tried-and-true choices, gardeners today can choose from an abundance of cultivars when creating a perennial garden. Creating that dramatic garden is a matter of both choosing the right plants and knowing how to combine them to best effect. Join the Massachusetts Horticultural Society and Laura Eisener of Laura Eisener Landscape Design on Thursday, May 17, at 7 pm at Elm Bank in Wellesley. Register online at www.masshort.org.  Based in Saugus, Massachusetts, Landscape Designer Laura Eisener also teaches at the Arnold Arboretum Landscape Design Institute of Harvard University.