If you've ever eaten an avocado from a grocery store, chances are you threw away the pit. The pit, which is the size of an egg, is actually a seed. You can start a new tree from that seed quite easily. Although the tree may take up to 15 years to mature to the point that it can produce new avocados, eventually you will have a tree full of avocado fruits. These fruits may not look like your original fruit, since most store avocados are hybrids. But you will have the satisfaction of having grown your own fruits.
Wash the avocado seed to remove any remaining pulp and let it dry two to three days.
Insert four toothpicks into the seed along a circumference two-thirds of the way down from the narrow end of the seed. The toothpicks should be located at points equidistant from one another.
Place the seed into the mouth of a quart jar with the wide end pointing downward so that the toothpicks prevent the seed from falling into the jar.
Fill the jar with water so that the bottom one-third of the seed is covered with the water.
Wait until roots form from the lower part of the seed and the top begins to split open and sprout.
Repot the avocado seedling in a 6-inch container with well-drained potting soil. Place the container in a sunny windowsill.
Repot the avocado in a slightly larger container after the plant becomes root-bound. Avocados do well when they're slightly root-bound. Transplant your avocado into a sunny location with well-drained soil if you live in zone 9 or warmer. If you live in zone 8 or cooler, leave your avocado tree in a container.
Check the soil weekly by inserting your finger into the soil up to your second knuckle. Water the plant when the soil appears dry. Avocado plants like soil that is as damp as a wrung-out sponge.