When the American Hosta Association held their national convention in Boston last month, they picked five gardens to show to visitors from around the country. One of those belongs to Mary Arnberg. Mary is not just an expert on the plantain lily, she’s a terrific speaker who combines humor with an encyclopedic knowledge of her subject. You’ll walk away with an appreciation for what may well be the most versatile garden plant around. Come to the Education Building at Elm Bank on Wednesday, August 3 at 7 pm for this continuation of the Wednesday at Elm Bank series. The cost to Massachusetts Horticultural Society members is $10, and non members will be charged $15. Refreshments and beverages are served. For directions, log on to www.masshort.org.