What Causes Yellow Leaves on Rose of Sharon?
Poorly drained soil is one of the primary reasons for rose of Sharon leaves turning yellow. The moisture can’t drain effectively and soggy soil suffocates the roots, which causes drying and yellowing rose of Sharon leaves. You may need to move the shrub to a more suitable location. Otherwise, improve drainage by digging a generous quantity of compost or bark mulch into the soil. Similarly, overwatering may be the culprit when leaves turn yellow on rose of Sharon (especially when overwatering is compounded by poorly drained soil). Allow the top 2 to 3 inches (5-7.5 cm.) of soil to dry, and then water deeply enough to soak the roots. Don’t water again until the top of the soil is dry. Watering in the morning is best, as watering late in the day doesn’t allow sufficient time for the leaves to dry, which may invite mildew and other moisture-related diseases. Rose of Sharon is relatively pest resistant, but pests such as aphids and whiteflies may be a problem. Both suck the juices from the plant, which can cause discoloration and yellowing rose of Sharon. These and other sap-sucking pests are usually easily controlled by regular applications of insecticidal soap or horticultural oil. Remember that a healthy tree, properly watered and fertilized, is more resistant to infestation. Chlorosis is a common condition that frequently causes the yellowing of shrubs. The problem, caused by insufficient iron in the soil, is usually ameliorated by applying iron chelate according to label directions. Inadequate fertilization, especially lack of nitrogen, may be the cause for rose of Sharon leaves turning yellow. However, don’t overdo it, as too much fertilizer can scorch the foliage and cause yellowing. Excessive fertilizer can also burn the roots and damage the plant. Apply fertilizer only to moist soil, and then water well to distribute the substance evenly.
