Thereâ€™s nothing more satisfying to a gardener than growing plants from seeds. From annuals and perennials to trees and shrubs, success can be achieved if you understand what triggers germination. Expert propagator Jack Alexander will share techniques for starting various types of plants from seeds in this Saturday, April 16 class at the Dana Greenhouse Classroom at the Arnold Arboretum. Students will leave class with a selection of seeds raring to grow. Aftercare will be necessary. Level: Beginner. Fee: $55 nonmember. To register, contact Marc Devokaitis at 617-384-5209, or log on to www.arboretum.harvard.edu.