Follow these steps to grow a plant from an avocado stone. Remember that it takes a very long time (up to 15 years) for the plant to produce fruit and that the avocados produced may be very different from the original variety.
Prepare the stone
Carefully wash the avocado stone. Use three toothpicks to suspend it in a glass with the broad end down. Fill the glass with water, so that the bottom inch of the stone is covered. Put the glass and stone in a warm location away from direct sun. Check the water level every day and refill it as needed.
Grow the stem and roots
After 2 to 6 weeks, the stone should sprout roots and a stem. Let the stem grow until it is about 7 inches long, then cut it back to about 3 inches long. Allow the roots to keep growing.
Plant the stone
When the stem has begun to leaf and the roots are thick, the stone is ready to plant. Use rich soil and a pot at least 10 inches in diameter. Plant the stone so the top half is exposed above the soil.
Care for the plant
Keep the soil moist, but don't saturate it. Frequent, light waterings are best. If the leaves begin to turn yellow, the soil is too moist, and you should let it dry for a few days before watering again. Let the plant grow in a sunny spot. When the stem is about 12 inches long, cut it back to 6 inches. This encourages new shoots to grow.