They could grow a sweet potato in water, in a clear glass container and watch the roots grow, stems and leaves grow.
this is not my idea,
Materials: 1 knee high pantyhose foot/student ----soil
-----rye grass seeds (can get at any nursery-cheap)----string----mugs ---variuos beads, toothpicks, etc. to decorate grass heads Procedure:
Drape the foot of the pantyhose into a mug, folding the top edges around the rim of the mug to hold the hose in place. Drop a generous amount of rye seeds in the bottom of the hose. Top with enough soil to make a small ball, the size of a tennis ball. Take the pantyhose off the mug and shake until the soils falls all the way to the bottom of the hose. Gather the top of the panty hose and tie with string to form a ball. Cut off any extra pantyhose. Put the grass heads in a shallow container and water generously. Continue to water daily until the grass hair begins to grow. After the hair has grown, the kids can decorate the heads with beads, toothpicks for earrings, etc. The cutest thing...you can gather a small portion of soil, tie w/ string, forming a small ball for the nose. This is hard to visualize, but they are really cute!