Avocados trees grow well from seed but do not grow true to variety. Most avocados are hybrid varieties, and the seeds may not reflect the characteristics of the parent tree. Another disadvantage of starting trees from seed is that seed-grown trees take up to 15 years to bear fruit, while commercially grown trees produced from grafted rootstock usually produce fruit within two to three years.
Avocado seeds are often started in water but must be transplanted into soil within a few weeks of sprouting if the tree is to survive long-term. The most reliable method is to start the seed in a small pot of soil while the seed is fresh and viable, then transplant into the garden in the spring.
Plant the avocado seed in a 4- to 6-inch pot of moist potting mix. Plant so that the pointed end of the seed faces up and is just visible above the top of the soil.
Place the pot in a sunny location and water the plant regularly to keep the soil moist, but not wet.
Withhold fertilizer until the roots are established, then fertilize with a water-soluble houseplant formula every two weeks.
Pinch off the top of the plant when it reaches approximately 12 inches in height. Topping the plant encourages branching for a fuller plant.
Repot the plant into a larger pot or transplant it outside in the early spring. If the avocado tree has been kept inside, move it outdoors for a few hours daily before transplanting. Increase the time outside daily until it is ready to be outside all day.
Transplant the tree to a well-drained site with plenty of space. Allow 20 feet of space between other trees, buildings and power lines.
Keep the area under the tree free of grass and weeds. Mulch under the tree will help keep weeds out but should not be allowed to touch the tree trunk.