Once the seedlings are about two inches high, have students measure the heights with Unifix cubes every three or four days. Provide data sheets for recording the height measurements and the number of days since planting. Provide a large calendar with the planting day prominently marked to help with this data collection procedure.

After a few weeks, when the plants reach full height, have students create bar graphs showing how their own plants grew each time they were measured.

In a follow-up discussion, be sure students realize that like humans, plants grow steadily at first, and then their growth slows or even stops. Unlike humans, however, many plants keep growing indefinitely, as long as they have enough nutrients and water and remain disease-free. Trees are a familiar example.