Yes, you can grow your own avocado tree from a pit—if you have patience.
Remove the pit from an avocado. Eat the flesh. Wash the pit and allow it to dry for 2 to 3 days.
Stick three toothpicks into the pit’s equator (or middle), equidistant apart and about ½-inch deep. Place the pit, with its fat base down, on the rim of a water glass, using the toothpicks to suspend it so that it doesn’t fall into the glass. Add enough water to the glass to cover about an inch of the pit.
Put the glass in a warm place out of direct sunlight. Add more water as needed. Roots and a stem should sprout in 2 to 6 weeks.
When the stem is 6 to 7 inches long, cut it back to about 3 inches.
When the roots are thick and the stem has grown out again, plant it in potting soil in an 8- to 10-inch-diameter pot, leaving the pit half exposed.
Set the pot in a sunny spot. Water the tree often, lightly, keeping the soil moist but not soaking wet. (Yellow leaves are a sign of too much water.)
When the tree is about a foot high, cut it back to 6 inches so that new shoots will sprout.
Your tree can live outside in the summer. Bring it indoors if winter temperatures go below 45°F.
Be patient! It may take 10 to 15 years for your tree to begin producing fruit. In the meantime, enjoy the plant.