The Kemper Center for Home Gardening at the Missouri Botanical Garden will give away Missouri native tree saplings on a first-come, first-served basis in honor of Arbor Day. (One per visitor.)
Master gardeners will be on hand to answer questions and give advice on planting trees.
9 a.m. to 5 p.m. or while supplies last.
More information: mobot.org
Explore the St. Louis Zoo after dark at Boo at the Zoo. Bring your little ghouls and goblins to this non-scary celebration designed just for kids. Though this is not a trick-or-treating experience, costumes are encouraged, and each child 12 and under will receive a treat bag when they leave.
Engage your young scientist in science-related learning at the Saint Louis Science Center's Preschool Science Series. Through interactive stories and hands-on exploration, children learn about science, as well as language, problem-solving and social skills.