Purchase a container with drainage that is at least four times the diameter of the seedling. The seedling, and especially the root system, should have plenty of room to grow, but you want a container that is easy to move around, too. Purchase a plant caddy, or an attachment with wheels, to make this task easier.
Plant your seedling as soon as you get it home, as delays can dry out the root system quickly.
Cut any long, stringy roots with pruning shears. Do not rip or tear the roots with your hands.
Fill the container three-quarters full with a premium potting soil.
Sprinkle the top of the potting soil with water until it is spongy-wet. Do not create puddles with the water.
Press the seedling into the soil. Then place extra soil over the roots until they are completely covered. Press the soil firmly with your hands, and add more soil, if necessary.
Cover the soil with 1 inch of mulch to keep the soil insulated.
Water the seedling thoroughly.
Keep the soil consistently moist, not soggy, during the first two years as the seedling grows. Water is vital to the development of the root system, but too much water can be harmful.
Move your seedling away from drafts, cold air and out of temperatures that dip below 50 degrees for the first few years. After this time, the seedling should be able to withstand harsher temperatures and periods with less water.
Watch the progress of your seedling. Depending on the species you have chosen, as well as where you live, your seedling should grow about six inches the first few years, and a great deal faster after that. Then, with a hearty and established root system, it should be ready to be planted outdoors.