Rhododendrons are a favorite plant of many gardeners on the East Coast. The high humidity and mild conditions with acidic soil contribute to easy growth. Moving a rhododendron is usually successful since the plant responds well to root and branch pruning. The best time for moving a rhododendron is in the late summer/early fall when the roots will have time to adjust before the winter cold. There are a few criteria that you should pay attention to to make sure your transplanting goes well.
Pull back any mulch that might be around the base of the plant. Rhododendrons have roots close to the surface so you should not have to dig very deep to get the plant out. Typically you can expect the roots to extend as far as the drip line around the top of the bush. Trim back any leggy branches that will just snap off anyway during the move.
Dig around the perimeter of the plant along the drip line. (The drip line is the area around the outside of the plant where the water will drip from the outermost branches.) Remove the soil as you work your way under the plant and try to keep as much soil around the roots as possible, especially if you are going to transplant it.
Pull the rhododendron out of the hole, keeping the root ball as intact as possible. If it is a larger ball, you may have to use a truck or heavy equipment just to lift it since the soil can be very heavy. Do not pull from the stem of the plant since it can be brittle and snap. Place ropes or straps around the outside of the root ball from which to pull.
Wrap the root ball with burlap to keep the roots from drying out and to hold on to as much of the soil as possible, unless you are just moving it to a new hole close by. Keep the plant watered and in the shade until it is ready to be planted in its new position.
Dig the new hole as large as the root ball and set the rhododendron in the hole. Remove as much of the burlap as possible by cutting it away so it won't constrict the growth of the roots. Pack the soil in around the plant and water well.