The success rate for transplanting dogwoods from the wild is very low. Very young trees that have seeded near an older specimen may do well if moved without disturbing the sensitive root system. Transplanting wild trees may also transplant diseases. You are most likely to be successful if you choose only small trees not over 3 feet tall. Whether this size or somewhat larger, you have to be careful to keep the root system intact as much as possible.
Dogwoods have many near-surface roots so don t disturb the soil around the tree more than necessary.
Dig with a sharp spade, preferably a sharpened King of Spades or similar tool to cut any roots cleanly rather than tearing them. This also helps keep the rootmass intact. Plan to support the root-mass as much as possible by sliding out of it s place onto burlap. Wrap the burlap up around the root-mass. Try to avoid wind-burn by also protecting upper tree when in transport.