Planting a potato in water is an excellent way for kids to see both sides of a plant's growth. Oftentimes, kids only see the growth of a plant above the soil, so it's fun for them to watch the roots expand in this simple experiment. Use a firm sweet potato. Insert toothpicks around the widest portion of the potato. The toothpicks will hold the potato in place once positioned inside a glass or jar. Place the pointiest tip into the water. The growth is very rapid and will not disappoint your little planters.
The basic concepts of planting a potato in water can be further expanded upon for older students, or any interested cultivator. The scientific method can be utilized by placing potatoes in different growth environments; one could be placed in plain water, one could be put into water enhanced with liquid food, and another could be planted in soil. Create a hypothesis for the growth of each potato and observe their development for a designated amount of time to determine the results.
Crafting a bonsai plant from a potato is time consuming and not entirely appropriate for impatient children. It can, however, be a very engaging and worthwhile experiment for those who are willing to wait. Use an already well-sprouted potato. Plant it in a shallow dish, preferably one constructed of clay. Cover it well, with just a bit of the potato's sprouted surface peeking out above the soil. Maintain a moist environment; a spray bottle is effective for daily misting. The potato's sprouts will begin producing leaves, but its upward growth will be stunted upon planting. The underside shoots, however, will continue to grow rapidly and will need to be cut back below the soil line. Trim the bonsai accordingly. Generally the height of a bonsai should be proportionate to the depth of its pot. Cutting off tip growth will prevent the plant from getting too tall, while encouraging outward branching.
A potato can creatively be used as a planter to demonstrate germination and seed growth. Cut both ends off of a potato and hollow out one side, using a melon baller. Scoop out enough of the potato to create a good sized cavity. Place cotton balls in the hollowed out portion and place, open-side up, on a small plate. Make a face on one side of the spud, using markers, paints, or various craft accessories such as squiggly eyes, or a fake mustache. Sprinkle grass seeds over the cotton balls, moisten with a spray bottle and place in a sunny spot. Within a day or two, the potato "face" will have a full head of hair.