Root Damage From Digging Rhododendrons

Rhododendron Roots

• Rhododendrons are sturdy, woody plants above ground, but below ground they're supported by a wide network of fibrous, silky roots that grow close to the soil's surface. The shallow roots spread far out from the crown, extending nearly as wide as the shrub itself.

Proper Digging of Rhododendrons

• The Azalea Society of America recommends digging a 12-inch deep trench around the outer perimeter of the shrub, then widening it in the direction of the shrub's center 1 inch at a time. Make the trench 18 inches deep for large, mature rhododendrons. Stop widening when you find roots in the soil, then slide the shovel underneath the root system. Tilting the shrub first to one side and then the other, slide a square of burlap larger than the root ball's diameter underneath the shrub, creating a sling to lift and move the plant with minimal root disturbance. Enlist some friends to help, since even small rhododendrons are heavy. If you're not replanting the shrub immediately, wrap the burlap around the root ball and secure it with twine. Keep the root ball moist but not soggy.

Wilting After Transplanting

• If too many roots are lost when a rhododendron is dug and transplanted, the remaining roots are unable to absorb enough water to keep the plant from wilting. If the soil is adequately moist but your plant continues to exhibit drought stress symptoms such as drooping leaves, flower buds that fail to open or brown, scorched-looking leaf spots, you must reduce the plant's canopy to compensate for the lost roots. Prune the stems back by one-quarter to one-third with hand pruners, making the cuts one-quarter inch above a leaf bud. Water the shrubs often enough to keep the soil moist but not soggy. You'll know the roots have re-established when new top growth appears.

Chlorosis From Transplant Shock

• Caused by an iron, manganese or zinc deficiency, chlorosis, a leaf disorder resulting from a lack of chlorophyll, is common in plants with damaged root systems. Rhododendrons that lose a significant percentage of their roots when dug cannot absorb enough minerals from the soil to maintain healthy foliage. Chlorosis first appears as lightening or yellowing of the leaf tissue between the veins, which remain dark green. Chlorosis caused by root damage is worse in soils with a high pH, since rhododendrons require acidic soil with a pH between 4.0 and 5.5 to properly absorb soil nutrients. If your transplanted rhododendron develops chlorosis, first check the soil pH and adjust it, if necessary; your garden center can recommend an appropriate soil additive. If the pH is satisfactory, remove approximately one-quarter of the rhododendron's top growth to compensate for root loss, then spray the remaining foliage with a water-soluble iron chelate solution. You may need to treat the plant several times before the root system recuperates.

Mulch Considerations

• With most plants, the first step in transplanting them is to remove the mulch over the root zone. However, rhododendrons have shallow, hair-like surface roots that grow up into the mulch layer. Always leave the mulch intact over your rhododendrons when digging in order to protect those roots.