Quaking aspen trees grow wild throughout the United States. They can grow anywhere from 20 to 80 feet in height, and their trunks are typically 3 to 18 inches in diameter. Aspen is considered a pioneer species, as they have a habit of springing up in forests that were recently destroyed by wind, fire or disease. Aspen needs full sunlight to grow to its full potential and is an extremely fast-growing tree in the right conditions. When other trees have died out, aspen is able to grow quickly in the available sunlight. However, it will die back when other trees overshadow it.
Purchase a quaking aspen tree from your local nursery. Few aspens are nursery grown. Most have been taken directly from their original forest. It is best to find a tree near the end of winter, as the tree will be dormant during the transfer to its new home. Planting after the last frost will also give the tree time to establish itself before the next harsh winter.
Find the permanent location for your tree. Aspen trees need full sunlight to thrive and will not tolerate any shade. An open area is best for aspen. However, as the trunk is thin and somewhat brittle, wind damage may be a problem. Consider planting your trees near a tall fence as a backdrop or on the north or east side of your house. If planting near the house, position the tree at least 10 to 20 feet away from the wall.
Prepare the soil. Dig a hole twice as wide and deep as the aspen's root ball. If planting more than one tree, space the holes 10 to 15 feet away from each other. Mix equal parts of compost and native soil. Aspen prefer medium to heavy soil, as long as the soil is well-draining and not clay-like. Aspen can tolerate sandy or silty soil, but water and nutrients will be more readily lost in this type of media. Add two handfuls of granulated fertilizer, high in nitrogen.
Fill the hole a quarter of the way with the soil mixture. Water the hole and allow the soil to settle, eliminating any air in the bottom of the hole.
Uncover the roots of the tree and spray water over them if they appear dry. Separate the roots so they are not tangled together. Gently place the tree in the hole and fill in the hole with the rest of the soil mixture. Water the area thoroughly and wait for the soil to settle again. Fill in any holes or cover any exposed roots.
Spread a layer of mulch 1 to 2 inches thick around the tree, leaving 10 to 15 centimeters around the stem uncovered. Consider laying a soaker hose under the mulch for the first 6 weeks. Aspen need a lot of water in their first weeks. Always allow the soil to dry slightly before watering the tree again. Drooping leaves indicate both underwatering and overwatering. Paying attention to your tree's appearance will tell you how much water is needed. Allow the soil to dry out more between waterings in the winter.
Once every early spring, apply a slow-release fertilizer. The fertilizer can be a general, balanced type, but fertilizer high in nitrogen will encourage faster growth.
Prune the trees every winter, removing any dead, diseased or crossing limbs. Aspen trees are very susceptible to disease. The best way to prevent tree death from disease is to keep the tree healthy and always remove any limbs that are not vigorous. Aspen trees also need to be kept thin. Branches cannot grow across each other, as this may cut sunlight from other parts of the tree.