While the most familiar technique of starting an avocado seed may be to stick toothpicks in the seed and suspend it in water, there is another way that is better for the plant. If planted loosely in potting soil, avocado seeds readily germinate. Kept in a humid environment and provided plenty of water and sun, an avocado seed germinates in about two months, on average. While a bit slower than sprouting in water, this method provides the soil the plant needs to grow beyond just a few inches in a glass container.
Select a ripe and soft avocado. Carefully remove the skin and flesh to reveal the seed within the fruit.
Allow the avocado seed to dry out for two to three days until the thin papery skin on the outside of the seed is loosened. Peel the skin from the avocado seed.
Fill a 6-inch plant pot with equal parts sand and potting soil. Dig a small hole large enough to hold the avocado seed.
Place the seed in the hole so that the broad end of it is in the soil and the pointed end is facing up. Cover the seed to within one-third of its top.
Water the soil so that it is damp, but not wet, and water regularly to keep the soil moist.
Place the avocado seed and the plant pot in a medium-size clear plastic bag. Poke several holes in the bag to allow for proper ventilation. Seal the mouth of the bag with a rubber band. This provides a humid environment for the avocado seed.
Place the planted avocado seed in a warm, well-lit area where it will receive at least six hours of indirect sunlight. Allow the seed to germinate for the next one to three months.
Remove the plant pot from the plastic bag when the avocado seed sprouts. Once the seed has a stem and several leaves, cover the remainder of the seed with soil. Pinch the tip of the seedling back when it's about 6 inches tall to encourage branching.