Use pits from healthy fruit
image by pat herman: sxc.hu
Avocado trees grow from pits acquired from avocado fruit. These hardy trees need plenty of sun to produce fruit but you can plant them in shade if you only want an ornamental tree. Transplant avocado trees outside in mild winter zones 9 through 11 or grow in a large, mobile container so you can move it inside during the winter in colder zones. It takes approximately 7 years for an avocado tree to bear its first fruit.
Choose a large, ripe avocado. Grocery store avocados are fine. Remove the pit from the fruit and rinse off.
Poke 3 holes equidistant apart around the center of the pit with a sharp nail. Stick a toothpick in each hole.
Fill a glass or jar with water and place a piece of activated charcoal in the bottom. Balance the toothpicks on the rim of the glass so the pit's flat end is in the water and the pointy end faces up.
Sit in a warm, sunny window to germinate. Refill the glass with water as needed to keep the bottom of the pit submerged. Germination may take up to 6 months to occur but usually takes less than 8 weeks.
Fill a 5-inch diameter container with 1 part vermiculite, 1 part sand and 1 part compost. Scoop out a shallow hole in the center of the growing medium and set the avocado roots into the hole. Cover the bottom third of the pit in soil.
Water the seedling well, then place in a warm area with 6 to 8 hours of daily sunlight. Keep the soil moist, but not soggy, at all times.
Transplant to a large tree pot or outside once the plant is approximately 3 feet tall. Fill a new container halfway with the potting mix. Grasp the tree by the central trunk near the base and gently pull it from the pot and set it on top the soil in the new pot. Fill in around it with soil.