Arborvitae is Turning Brown

Check where the browning occurs and when. Remove any loose leaves and debris that have dropped onto the ground around the base of the tree. Browning near the trunk in the fall or several months after transplantation is normal. Relax and take a deep breath if most of the brown leaves are in the center of the tree, not on the tips or throughout the tree. Trees will drop up to one-third of their leaves in the fall before dormancy. The discarded plant material provides good mulch around the base of the tree.

Dig a shallow trench around the base of the tree with a hand spade and check the soil condition. The soil should be loose and moist. Water the tree once a week from March through August with a soaker hose on a slow drip until the soil is moist to a depth of 12 inches. Do not over- or under-water as both conditions cause browning and eventual tree death. Transplant the tree to a different location if conditions leave the roots standing in water.

Watch the tree during the day and verify that it gets six to eight hours of full sun. The arborvitae will brown from lack of sun. Transplant the tree to a new location if it receives too much shade.

Check the tree for pests. Place a large circle of white paper under the plant and shake it to dislodge any plant material and pests. Scoop up and bag any insects you see. Small spider mites will slowly crawl off the paper and look like small moving periods. Aphids, sawfly larvae, arborvitae larvae, bagworms and cedar tree borers feast on arborvitae. Carry any pest you isolate to an arborist or county extension agent to identify it and select the proper pesticide.

Mist a mixture of 1 quart water, 1-1/2 tablespoons neem oil and a drop of liquid soap on the tree to repel insects and interrupt their reproduction cycle. Neem oil is environmentally-friendly, nontoxic to humans and pets and an organic alternative to chemical sprays. Neem oil kills scale and fungal infections that cause arborvitae browning. Horticultural oil prevents mites when sprayed on the tree between November and April.

Wrap a newly transplanted tree in burlap for the first three winters to prevent the browning that can accompany winter burn. Stop watering the tree in late August and rely on rain so the tree will cut back on new growth and harden for the winter.