Transplanting Large Shrubs
Techniques for safely moviing mature plants
How do I move a rhododendron that's too near the front steps? It's 5 feet tall and about 3 feet across, and I'd like to move it to a point about 15 feet away, where it will have room to grow larger.
— Cliff, Redwood City, CA
Roger Cook replies: Rhodys are among the easiest plants to move. What's most important, however, is the care administered afterward. That determines whether the move is successful.
The first step is to tag the best side of the plant so you'll have no trouble positioning it for best effect later on. Then tie up the shrub's branches so you can dig around it more easily. I use heavy two-strand jute twine circled around several times. Now dig a trench around the root ball. The rule of thumb is to make the ball 10 to 12 inches in diameter for every inch of stem diameter. In your case, the main stem is probably about 3 inches thick, so the ball should be 30 to 36 inches in diameter. Using a regular spade, make a 12- to 18-inch-deep trench around the plant. Chop through the roots with the blade held vertically, its back toward the stem. Using a hand pruner or loppers, sever any roots the shovel can't, and make clean cuts on any ripped roots.
With the trench complete, slip your spade as far under the ball as you can and lift up gently so you don't break the handle. If the plant doesn't lift easily, there might be a root going straight down; cut it with the loppers.
nce the plant is free, I typically wrap the ball in burlap, but since you're going such a short distance, you can just drag it to the new location on a heavy-duty tarp. If the plant isn't too heavy, two people can lift it onto the tarp by grasping it low on the main stem. Another approach is to tip the plant one way and slip the tarp beneath, then tip it the other way and pull the tarp under.
Dig the receiving hole slightly shallower than the old one — never put a plant in deeper than it was originally — and about two or three times the diameter of the ball. Lift the rhody into its new hole, then fill in around the root ball with compost mixed into the excavated soil. Rhodys love soil with a lot of organic material, and I like to add in some low-nitrogen, high-phosphorus fertilizer, which promotes root growth. Use any extra soil to make a temporary ring around the shrub outside the ball, not on top of it, then flood the area with water two or three times to settle the earth. Resist the temptation to pack the soil with your boot.
Finally, rake the ring flat and apply 2 to 3 inches of organic mulch over the ball, but not in contact with the main stem. Then just cut the jute twine and water your rhody as needed to keep the root ball moist.