Every time you eat an avocado, you have the opportunity to grow an avocado tree. A fun and educational project for kids and adults alike, planting avocado seeds is simple. If you live in a warm climate, your avocado can eventually move outdoors year-round. If you live in a climate with cold winters, your avocado must come indoors in the winter. Note that no matter what type of avocado your seed came from, the resulting tree may be a bit different than its parent.
Rinse any remaining avocado meat off the seed. Identify the flat side of the seed and set it on a table facing downward.
Poke three toothpicks into the seed, at approximately an equal distance around the sides.
Fill the glass jar with water and suspend the avocado seed on the jar's rim, using the toothpicks. Submerge the flat side of the seed in the water, so that it is covered by about an inch.
Place the jar somewhere warm, away from drafts and direct sunlight; the seed will germinate in a couple weeks. Trim the plant by half when it reaches 6 inches tall, using pruning shears. Place the plant in direct sunlight once it has sprouted.
Add water whenever the water line recedes down the sides of the seed. Change the water whenever it looks dirty.
Plant the seedling in a 12-inch pot filled with potting soil after it has grown 7 inches tall (for the second time, after you trimmed it previously). Leave the top of the seed exposed above the soil, but cover the roots completely.
Water consistently, so that soil is always moist (but not soggy). Fertilize with a balanced liquid fertilizer once a week, according to package instructions.