Plant an herb garden with the third graders. Give each child a small pot, some planting soil and a plant such as basil, sage, mint or thyme. Instruct the children to place the ball, or bottom of the plant, several inches deep into the potted soil. Have them water their plants and place along a window sill. Teach them the importance of monitoring water levels and turning the plants to face the sun from different angles every few days. Allow them to check their plants and their classmate's plants every morning.
Take third graders on nature walks around the school campus or do a "mental" nature walk having the children close their eyes and imagine walking in a forest. Converse with the children about what different plants are seen or imagined. Talk about foods they enjoy that are made from plants and why various plants grow in the places they do. Ask them what plants do for the atmosphere, for medicine or other uses they may have.
If there is a small section of usable space on the school grounds, plant a small garden. Allow the children to help decide what items to plant. Instruct them in ways to grow plants from seeds or from seedlings. Let them take turns turning over the soil and planting seeds or seedlings. Watering can be done on a "take-turn" basis incorporating the aid of other classes studying plant life. The children will enjoy watching and eating the fruits of their labor.
Incorporate a theme into the third grade classroom. Pick a geographical area such as tropical forests, prairie states or a country. Help the students make posters depicting the theme of the area chosen. Make poster board trees, grasses, flowers or food plants to fit the area. Turn the classroom into tropical forest, for instance, by adding cut-out monkeys in trees, rain sounds from a recorder and plenty of large plants that can be found in the tropical forest. Aid students in discovering what plants would be found and what they might be used for.
Using worksheets, drawings and lectures, discuss different ways seeds are dispersed, their life cycle and their uses. Help students draw charts or keep notebooks about how different seeds develop. Use worksheets where children label parts of a plant in different colors or draw lines between various plants and how their seeds might be dispersed. Imagination and interesting lesson plans will help third graders enjoy learning about plants.