Purchase grass seeds at the garden center of a home-improvement store or department store. Common grass seeds include Bermuda, Bahia, St. Augustine and Zoysia. Alternatively, purchase wheat berry seeds at a nursery or a natural foods store. If using wheat berry seeds, soak them overnight. The best time to plant grass seed is in the fall and the spring.
Purchase potting soil or collect soil from the garden. Preschoolers can help check for debris such as sticks and stones and remove them. If there are any clumps of soil that are larger than a half dollar, break them up. Be sure that the potting soil is moist. If it is not, allow children to mist the soil with water in a water bottle. Preschoolers can use a shovel to help fill a shallow, rimmed tray with about 2 inches of soil.
Preschoolers can help plant the grass seeds. Position letter cookie cutters on top of the soil to create the message for the project. Arrange the cookie cutters so that they are at least one-half inch apart. Preschoolers can sprinkle a single layer of grass seeds into each cookie cutter. Show them how to press the seeds into the soil with their fingertips. Gently remove the cookie cutters up from the soil. Cover the seeds with 1/4 inch of soil. Water the soil until it is moist throughout. Place the tray in a windowsill that gets plenty of sunlight.
Once the grass seeds have been planted, preschoolers can observe the grass seeds as they grow. Children can take turns watering the plant lightly, once per day. Supervise children so that they do not saturate the seeds. Create a chart so that each preschooler can keep track of his responsibilities. Also keep a chart to record observations. Ask children to predict when the grass seeds will sprout. When the seeds have sprouted, determine which preschooler had the closest guess.