Fall is the time to plant trees. However, not all trees are healthy when purchased. Here are some considerations when choosing a tree.
Smaller trees are less expensive and establish a root system quicker, requiring several months of irrigation. The disadvantage is an immature, small landscape for a number of years.
Large trees are more expensive and may take years to establish a root system, relying much longer on supplemental irrigation. The advantage is establishing a mature landscape much quicker.
A field-grown tree is dug with a tree spade and wrapped in burlap and a wire basket, often referred to as balled-in-burlap, or B and B. This method is typically done for trees with a 2-inch caliper (diameter of trunk measured at breast height) or larger. They are too heavy to move by hand and are typically reserved for commercial installation using tree dollies or heavy machinery.
Container-grown trees are found at garden centers growing in plastic pots of 3, 5, 10 or 15 gallons or larger. Since they are not dug from the field, there is no root loss at planting. When trees remain in pots too long, however, the roots begin to circle around the perimeter. Root-bound trees establish slowly, if at all.
Air-pruned containers are plastic pots with holes along the sides and bottom. When roots reach the edge, the root tip dies back and prevents circling. Root systems in air-pruned pots can be more fibrous without being root bound.
Copper-coated containers have copper material on the inside of the pot that prevents roots from circling.
Tree trunks should have a wider base and taper upward for stability. A container-grown tree that is staked too long may not develop the structure to stand on its own when planted.
Check for insects and disease along the branches and leaves. These ailments may not be a deal breaker since they can be treated. For instance, aphids will not threaten the health of the tree. If leaves and stems are dying at the tips, however, this could be a sign of something endemic and incurable. Look for healthy tissue all the way to the end of branches.
Always inspect the trunk for handling damage. Injuries can occur during loading and transportation and may not affect the rest of the tree until much later.
Don't forget about the root ball. Start by pushing the tree trunk back and forth. If the base of the trunk moves loosely, this could indicate a poorly established root system. Scrape the soil away from the top of the root ball. The roots should be at or near the surface rather than buried. The thicker main roots should not be crossing or wrapping around the base of the tree. This will lead to problems.
Finally, tip the tree on its side and slide it out of the pot. Root-bound trees are difficult to remove with a significant amount of roots growing out of the bottom. Once out of the container, tightly wound roots that take the shape of the pot are an indication of root-bound root balls. If planting a tree with this characteristic, cut three lines along the perimeter and an X along the bottom with a utility knife to stop the circling growth.
If the bottom half of the root ball falls off, this could indicate root rot disease from overwatering and would not be advisable to purchase. A closer inspection would indicate brown, mushy roots that strip off easily.
Occasionally, in spring, a smaller root ball can be pulled from a larger pot, indicating the tree hasn't had time to grow into the container. While this may not harm the health of the tree, you would essentially be overpaying for the tree.