Ken Druse, whose books the New York Times describes as “bibles for serious gardeners,” will discuss shade gardening and offer highlights from his new book, “The New Shade Garden: Creating a Lush Oasis in the Age of Climate Change.” This date is also a Garden Conservancy Open Day, and Margaret Roach opens her garden to visitors. Broken Arrow Nursery, growers of rare and unusual plants, will sell shrubs, perennials, and trees from a pop-up shop at Margaret’s home.