Tree transplanting shock occurs in new trees brought home from the nursery and in existing landscape trees that are dug up and planted elsewhere. The horticultural equivalent of failure to thrive, transplanting shock can be prevented with proper planning and good follow-up, and cases vary in severity.
According to North Dakota State University, two major causes of tree transplanting shock are placing the tree in too small of a hole and giving the tree the wrong amount of water in the weeks after transplanting. The university recommends leaving the tree 12 inches of soil ball per every inch of tree trunk diameter (which is 12 inches of root and soil per inch of tree diameter). Trees need a deep soak every 10 to 14 days. If you're not sure whether to water, check the soil's moisture content 3 to 4 inches below the soil surface: if the soil here is still wet, delay watering until it becomes dry.
The best way to prevent tree transplanting shock is to consider the needs of your tree before you transplant. If your tree loves sun, don't transplant it into a shadier environment. Avoid placing the tree in unnecessary stress by transplanting at a poor time of year, such as fall. Fall-transplanted trees are often still in shock when winter hits, and they can suffer from not being adapted to the cold.
One main symptom of transplanting shock is reduced vigor. Trees appear to grow very little or not at all. Some branches may die, losing foliage and becoming brittle. Trees that aren't receiving enough water after transplanting may appear wilted or shriveled.
Prevent tree transplanting shock by only moving trees when it's necessary, such as when they've outgrown their existing site or appear to be faring poorly in that site. Then select a new site that suits their growing conditions and wait for early spring, when the tree is dormant but the soil is warm enough to be worked. Trees planted at this time have a better chance of adapting to the new environment before winter. Also, only grow trees suited to your climate.
If your tree does show signs of transplanting shock, it may die or it may suffer for an extended time period. You can expect a tree to suffer from transplanting shock without dying for up to three years, notes the University of Kentucky. Not all trees take this long to recover, though.