Repotted plants that are not root pruned may appear healthy but really are not. Check for soils of different consistencies or remnants of a fiber pot as indicators of trees that have been shifted up. To check for well-rooted plants, grasp the trunk of the tree near the base and try to move the tree in the container. Well-rooted plants should not create a hole in the soil when the stem is shaken. The container and the tree should move as one.
Healthy roots are firm and usually lighter in color than the surrounding soil.
There should be no offensive odor or mushiness. Carry trees by their container or root ball rather than by their trunks to avoid damaging their root systems. The ball should not have cracks in the soil or large clumps of loose soil. If it does, these are indications of improper handling which could mean trouble later on. Buy nursery stock from reliable nurseries which are knowledgeable about the plants they sell, offer plant guarantees, and practice proper handling and care of their nursery stock.