Keeping Arborvitae Green

Are Your Arborvitae Green?

Arborvitae, in Latin, means “tree of life.” At The Home Depot in Colorado, we’ve been hearing lots of reports of arborvitae blight. Discolored, brown, dry foliage is a sign of blight. While we are not aware of any epidemic attacking arborvitae, common conditions might be the cause of some problems within the species in this locale.

If your arborvitae have turned brown, these are the things you should check. It is common for arborvitae to temporarily lose color during the winter and drop some of its small, inner branches, but the trees usually bounce back in the spring and make up for its losses with new growth.

NEW GROWTH
If there is new growth, your tree is still alive. If there is no new growth, scratch the woody bark near the trunk to see if there is green below. If so, simple remedies may bring it back.

DRY SOIL
Dig within a few inches of the trunk to a depth of about six inches. Feel the soil. If it is dry, your major problem may be lack of water. Many homeowners don’t realize that Front Range winters are very, very DRY. Many of your trees and perennials will benefit from consistent winter watering, taking snow and natural precipitation into account.

Give your arborvitae water each day for 3-4 weeks to nurse them back to health. Measure the trunk at knee level. For each inch in diameter, provide 10 gallons of water every 10 days. It seems like lots of water, but that’s what these hydrophilic evergreens love. A steady drip from a garden hose is fine, and the standard residential hose delivers 10 gallons of water in five minutes.

Water the soil directly. Watering the lacy foliage may contribute to sunburn.

Add polymer crystals beneath the surface of the soil around your trees and shrubs. These little crystals will balloon to the size of a grape and gradually release water to plant roots as needed.

IRON DEFICIENT SOIL
Colorado soil is notoriously iron deficient. Add some Ironite, or other iron additive, to your normal fertilizer mix.

MULCH
Pine bark mulch and pine needles are natural forestation by-products that will help retain water and add beneficial nutritional elements to your arborvitae bed.

FUNGAL INFECTION
The browning might be caused by a fungal infection. The Home Depot offers a variety of remedies. To keep a fungal infection from spreading, prune the branches at least 3 inches before the browning. With each cut, sterilize your pruners in a 15% bleach or alcohol solution. Collect the cuttings and immediately bag them, keeping them away from the host plant and any other plants.

LEAFMINERS
Leafminers are an insect that burrows in the foliage of arborvitae (and citrus leaves!). Leafminers are easier to see on plants with flat leaves than in arborvitae, but they leave discolored trails where they’ve traveled. Prune with sterilized pruners, as described above. Then, treat with one of the Sevin products containing carbaryl.