Why Are My Hydrangeas Brown?

Leafties can be detrimental to hydrangea leaves, causing them to turn brown. They can also cause them to curl and weave together. Leafties are green caterpillars with brown heads that are around a half-inch in length. The leaftie larvae bind the leaves together for their own safety while they are eating. They should be manually removed. The larvae can be squashed on the leaves and sprayed with an insecticide.

Video: Hydrangea Care 101

Spider mites may be the cause behind leaves that turn brown or have a burned look to them. The leaves need a daily morning spraying for up to four days. An insecticidal soap can be applied if the spider mite assault is more intense.

Cercospora leaf spot is a disease that can affect hydrangeas. Brown or purple spots will appear at the base of the hydrangea. The infection becomes more rampant as the infected leaves begin to drop off the plant and the infection spreads. It does not typically kill the plant, but the leaves should be removed. Nitrogen can be applied to slow leaf spot growth. A fungicide may be applied to ward off future leaf infection.

Anthracnose is a fungus that can cause infection on the blooms and the leaves of hydrangea. Moist, hot weather tends to cause the disease to spread more. Circular or uneven brown spots that are 1 inch wide will appear initially. They may then change to a lighter shade of brown and then a tan color. Fungicides can be applied to counteract the anthracnose damage. It should be treated during the summer for 10 to 14 day periods.

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Phytophtora root rot is a fungus that can cause the tissues around the crown of the hydrangea to turn brown. It can then rise up the stem. It can also stunt the growth of leaves and cause them to become brittle and break off. Fungicides are effective treatments for this fungus.