Ask Mr. Smarty Plants

Ordinarily, our first recommendation is to do that in the late Fall or Winter, when the tree is semi-dormant. Cercis canadensis (eastern redbud) is native to your area at the mouth of the Chesapeake Bay, according to our Plants of Chesapeake Bay list in our Special Collections section.   In Austin, Central Texas, USDA Hardiness Zone 8a, our redbuds have already bloomed, leafed out and are beginning to show some seed pods. In Fairfax County, you are in Zone 7a to 8, very near ours, and we would hate for the tree to be moved while it is in bloom, because almost certainly you would lose the blooms. No matter how carefully you do so, it is always a shock to move a tree, and we believe it would be preferable to wait until Fall to do so. However, if there is some compelling reason, such as construction in the area where the tree is now, then the sooner you get it moved, the better. The research we have seen indicates that a young tree can be successfully transplanted in Spring or Fall. 

For more information on the tree itself, read this USDA Forest Service article on Eastern Redbud. Some more specific instructions are found in this eHow website How to Grow a Redbud Tree. Even with your best efforts and planting it in the cooler Spring, you may still have some leaf loss. This is transplant shock, and if it begins to bother you, trim off about 1/4 of the crown. Mostly what that tree will be doing this year is getting its roots back into working order. Don't fertilize! In the first place, fertilizer is to encourage new growth, which the roots don't have the time or energy for at first. In the second place, fertilizer can actually shock those little new rootlets that are trying to get going in the new soil and access nutrients from the soil. Trimming off some of those upper stems and leaves reduces the transpiration, or loss of water, that the roots must supply. Don't trim off too many leaves, though, they are needed for photosynthesis to provide nutrition to the whole tree.