Something Is Killing My Hydrangea

Pests

• Hydrangeas are generally healthy plants, and the presence of pests is often a sign of an underlying problem. Aphids are fairly common and if left uncheck may cause severe, but not usually lethal defoliation to the shrub. Leaftiers are green caterpillars that are most active in the spring. If left untreated, leaftiers will severely defoliate a hydrangea, which may lead to plant death. Additional concerns include rose chafers, oyster scale and spider mites. Most of these pests may be controlled by introducing natural pests, the most common of which are ladybugs, or by applying a dose of insecticide or horticultural soap.

Disease

• Fungal and bacterial diseases are prominent when excessive rain or humidity is present in the environment. Root rot is a fairly common disease that occurs when bacteria enters the roots, turning them to a useless mushy material. Once symptoms, including stunted growth and leaf yellowing, are present, it is often too late for treatment. Powdery mildew, which produces a dust-like covering on the leaves, is rarely fatal. Additional problems may come from cercospora leaf spot, anthracnose fungi and botrytis blight that may be treated with fungicidal sprays and thorough cleaning of dead or fallen debris.

Environmental Problems

• As with most other plant species, if hydrangeas are not supplied with the proper environment, severe damage, growth reduction and death may result. Once established, hydrangeas require moderate amounts of water, approximately 1 inch per week. In times of drought or long periods of heat, it may be necessary to provide more water. Soil should be kept moist, not wet, and should provide good drainage and plenty of nutrition. Slightly acidic soil and afternoon shade are ideal for optimal flower production. If these conditions are not met, plant health may deteriorate and lead to death.

Nutrient Deficiency

• About 16 nutrients are required to keep a plant healthy. When even one of these is in short supply, it may lead to death. Among the most common are nitrogen and iron deficiencies. Both elements are essential in producing chlorophyll, and without it leaves will turn yellow and die. Both problems should be corrected as soon as possible to prevent irreversible damage. Growers should mix in a bit of compost that is heavy in decayed organic matter. This will correct nutrition, drainage problems and improve air flow to roots. A nitrogen-rich fertilizer may be applied, which will correct nitrogen deficiency quicker, but may result in root and leaf damage if not applied correctly.