Take your child to a garden and talk with him about what he sees there. Let him smell herbs and flowers and compare leaf shapes, sizes, textures, colors, and patterns. Ask him open-ended questions to get him to think about what he's experiencing with all of his senses. If you're in your own garden, turn the hose to a trickle and ask your child to water the plants. Buy him some seeds and give him a flowerpot so he can plant them and, over time, see how they grow.
Interacting with the natural world enhances your child's sensitivity to plants and animals and helps him understand the relationships and connections among all living things.