I recently saw two products which I think are great for children.  The first are Eco Plants, which have a variety of things to grow like aloe, basil, cactus, and a venus fly trap).  Go to http://www.Dunecraft.com for find out more information.  (They are priced at $2.99)

The second is a, “Matchstick Garden” for beginner planters, too cute!  Go to http://www.Ahamodernliving.com to view them.

Children love to get their hands dirty, and watch as their plant grows.  They can make a planting journal to track weekly their findings and make a prediction for each week.  This can be done as early as two, all the way to adulthood, lol!  Great activity for the summer!