Next time you slice an avocado for a salad or sandwich, or mash one for guacamole, don't throw away the seed. With very little effort and practically no expense, you can turn an avocado seed into a large, lovely houseplant. Planting an avocado seed is a good way to introduce kids to the pleasure of gardening, but can be fun for seasoned gardeners, as well. Don't expect avocados to grow on your plant, as avocados can take up to 20 years to develop, and are rarely produced on indoor-grown avocados.
Rinse the avocado pit under warm running water, and remove all of the pulp. Set the avocado pit aside until the brown covering dries and begins to crack.
Fill a 6-inch pot with commercial potting mixture for African violets. Spray the potting mixture with a spray bottle until the soil is damp clear through, but not dripping wet.
Plant the avocado pit in the soil with the bottom half of the pit in the soil and the pointy top half above the soil. Place the pot in a plastic bag, and secure the plastic bag around the pot with a rubber band. Poke a few holes in the plastic bag so the avocado pit will have air circulation.
Place the pot in a warm room where the avocado pit will be in bright, indirect light. Avoid hot, sunny windows. You should see sprouts appear in one to four months.
Remove the plastic bag when the avocado seed sprouts. Move the new avocado plant into bright sunlight.
Water the avocado plant regularly, and don't allow the soil to dry out. The potting mixture should be moist, but not soggy.
Fertilize the avocado plant once every month during spring and summer, using a liquid houseplant fertilizer. Don't fertilize the plant during fall and winter.
Pinch new growth on the avocado plant so that the plant will grow bushy instead of tall and spindly. Every time you see a pair of tiny, new leaves, pinch them off with your fingernails and the plant will grow two new branches at that point. Pinch the new growth on those new branches, and continue pinching new growth as needed until the plant has a rounded, compact appearance.