Fill a plastic toy dump truck with organic potting soil.
Plant several nasturtium seeds about 1/4 inch deep in the mound of dirt and cover lightly with soil. Put in a sunny spot.
Water when the soil starts to dry out, about twice a week. The seeds should sprout in about 5 to 12 days.
The spindly plant's leaves look like small lily pads; the yellow and orange blooms are edible and have a spicy bite. Your child can throw them in a salad, or even put them on a sandwich if he's feeling daring.
We used Tonka's Chuck My Talking Dump Truck, $15, hasbro.com