Spring Wildflower Symposium and Plant Sale at Wintergreen Nature Foundation Trillium House at Wintergreen Resort. We are pleased to have a diverse group of instructors for our 40th Spring Wildflower Symposium, including well-known botanists, geologists, authors and artists, each prepared with a full weekend of activities to reconnect you with nature. Walk our trails, view the gardens, and enjoy everything we have to offer this weekend! Fee. Payment is due at time of registration. Advance registration required. May 16 9AM to 2PM. Spring Wildflower Symposium Plant Sale at The Nature Foundation. Enhance your property with adaptable, sustainable, and beautiful native plants, all propagated and grown from local seeds and cuttings. 434-325-8169.