Rhododendrons are irresistible in springtime whether you fall for California rhododendron (Rhododendron macrophyllum), the showiest native shrub in the Pacific Northwest, or one of its cultivated cousins. Cultivar colors range from pure white through deep purple, and include cream and yellow, the palest pinks to scarlet, lilac and blue; many thrive in a Mediterranean climate. These shrubs need afternoon shade and well-draining, acidic soil to thrive, and resent any interference with their shallow roots. If transplanting becomes absolutely necessary, root prune first to help your rhododendron make the move successfully.
Measure the circumference of your rhododendron stem or trunk. If the plant is a shrub, measure the stem at its thickest point. If it is a tree, measure about a yard above the soil.
Determine the diameter of the stem or trunk by dividing the circumference by 3.14. To transplant the rhododendron, you'll need to dig out a root ball that is 1 foot wide for every inch of trunk diameter. For example, if you have a rhododendron tree with a trunk circumference of 6.28 inches, its diameter would be 2 inches and its root ball must be at least 2 feet wide.
Draw a circle on the soil with the rhododendron trunk at its center. Make the circle at least as wide as the minimum size of the root ball. Press a sharp spade into the circle circumference to a depth of 10 inches. Remove the spade and repeat the action until the entire circle circumference is cut to a depth of 10 inches. This prunes the plant's longer roots and encourages new, shorter roots to form. Act during the rhododendron's dormancy at least three to six months before transplanting day.
Shovel a trench around the rhododendron the day you transplant it, selecting a day during its dormancy. Make the trench no closer to the plant than the circle you traced months before. Dig out the trench until you can slip the shovel beneath the plant's root ball. Loosen the root ball by moving the shovel from side to side, then lift the root ball out of the ground.
Things You Will Need
- Measuring tape
- Prepare the new planting spot for your rhododendron before you even begin to dig the trench. Work the soil in the new site. Dig a planting hole as deep as the root ball and several times as wide.
- Do not allow the rhododendron roots to see the sun. If you must transport it a distance to replant, cover the roots with a tarp or wet blanket.
- Royal Horticultural Society: Rhododendron
- Missouri Botanical Gardens: Rhododendron Prinophyllum
- Wayside Gardens Voices: Azalea and Rhododendron Pruning
- Sunset: How to Transplant Shrubs, Trees
- Missouri Botanical Gardens: Gardening Help FAQs
- Lady Bird Johnson Wildflower Center: Native Plant Database: Rhododendron Macrophyllum
- Liz Gregg/Photodisc/Getty Images