Caution: A few days before you dig, call 811 to have your underground utilities marked.
If you plant the root-ball of a tree too deep, new roots can girdle the trunk and may also suffer from a lack of oxygen. Plant a tree so the root collar—where the uppermost roots attach to the trunk—is about an inch above the soil level.
In many cases, containerized trees from nurseries are planted too deep. Don’t go by the soil level in the container. Dig down into the planting medium to find the root collar so you know how deep to plant the tree.
If you’re planting a bare-root tree, leave a cone of soil at the bottom of the planting hole and set the root system on top. Place the handle of your shovel flat across the hole from one side to the other to make sure the crown is level with the surrounding soil. You should be able to partially see the root collar, or trunk flare, after the tree is planted.
The ideal time to plant a tree is in early spring before “bud break” or in the fall before the tree goes dormant. Cool weather allows the tree to establish roots in its new location before new top growth puts too much demand on it. Some trees establish better if planted in early spring. These include oaks, pines, dogwoods, American holly, willows and black gum. Avoid planting trees during the summer when they’re in full leaf and susceptible to heat stress.
Dig a saucer-shape hole three to five times the diameter of the root-ball (or the spread of the roots for a bare-root tree). This allows the roots to easily penetrate the softened backfill and properly anchor the tree.
If you’re planting in clay or wet soil, use a garden fork or your spade to roughen the bottom and sides of the planting hole to avoid “glazing.” Glazing happens when the sides and bottom of a hole become so smooth and compacted that water can’t pass easily through the soil. In extreme situations, it could block roots from penetrating the sides of the planting hole.