The seeds from grocery store avocados (Persea americana) sprout and grow into a lush houseplant if properly planted. These seeds are often germinated in a glass of water, with toothpicks inserted into the sides to support the seed so it's isn't completely submerged. Although avocados can grow into 30-foot or taller trees in U.S. Department of Agriculture plant hardiness zones 10 through 12, they are often grown as much smaller houseplants in cooler climates. The seed requires transplanting into a pot of soil after it germinates if it's to continue growing healthy roots and foliage.
Fill an 8-inch diameter pot one-third to one-half full with a standard potting soil mixture. Use a pot with a bottom drainage hole and water the soil until the excess moisture drips from the hole. Form the soil into a 1-inch-tall mound in the center.
Lift the avocado seed out of the water in which it germinated, handling it gently around its center so you don't disturb the roots or top growth on the seed. Pull the toothpicks from the seed carefully.
Set the seed in the pot, allowing the roots to trail down the side of the mound. Remove the seed and adjust the soil depth, if necessary, so the top of the seed sits 1 inch beneath the rim of the pot. Fill in around the seed with additional soil until the top of the seed sits just beneath the soil surface.
Water the soil a second time until water begins to drain from the pot bottom. Add more soil, if needed, after watering settles the soil further around the seed.
Set the avocado in a location that receives bright, indirect sunlight in summer and direct sunlight in winter. Water the soil when the top 1 inch begins to feel dry.