You spark their interest in gardening. The knowledge will inspire them to do other things scientifically. Pinckney's Farley Hill Elementary has a project called Schoolyard Habitat where parents, teachers, and students work together to improve their natural surroundings. Last spring, Hornung students planted pumpkins and popcorn to harvest this fall. It also develops a respect for the natural environment.
Science is hard to retain unless they see how it relates to their everyday life.
You never know what will cause a child to connect. I did it at my old school, Voyager. I help with my mom's garden, too. She grows tomatoes, peas and lots and lots of flowers. You get to make a mess.