You and your child can start a garden in almost any container. Cardboard egg cartons are ideal for starting seeds and observing sprouts. You also can put seeds in a plastic storage bag full of dirt so your child can see how roots spread down into the dirt as the sprout finds its way up to the surface. Transfer the sprouts to larger pots or a garden plot as they develop. Plants that grow quickly and produce food your child can eat right out of the garden are pea pods, string beans, radishes and carrots.
To plant a bucket garden, fill a 5-gallon bucket with dirt and composted soil, dig a hole in the center, crack an egg into the soil for extra fertilizer and plant a tomato seed over the top of the egg. Plant herbs and smaller vegetables around the perimeter of the bucket. Explain to your child each step of the planting process and what the fertilizer is for as well as the seeds' need for sunlight and water. Track the vegetables' growth with your child.
To make a grass head, take a knee-high length of nylon hose and put a handful of grass seed into the toe. Next take a softball-sized clump of dirt and place it in the nylon on top of the seeds. Tie the nylon off under the ball of dirt and leave about three inches of dangling nylon. Place the dangling nylon in a cup of water with the ball of dirt on top of the cup. Water will absorb through the nylon to the dirt. Also mist the ball once or twice a day. As you and your child watch the grass seeds sprout into a hairdo, you can decorate the nylon with googly eyes and a pipe cleaner smile.
You also can plant grass seeds in a small cup of dirt and decorate the cup as a face.
Encourage your child to keep a journal of your plantings. She can document growth and draw pictures of the process. To make it more of an experiment, plant the same seeds in different soils with different sun exposure and give the seeds different amounts of fertilizer and water. Document differences in growth and production. Or plant a variety of vegetable seeds in one plot and keep track of which seed is the first to sprout, which is the first to blossom and which is the first to produce fruit.
For a flower garden experiment, have your child see how many different species of flowers she can plant that are all the same color. Or ask your child to try to create a pattern such as a flag or rainbow by plantings seeds that produce flowers in a variety of colors.