Why Is My Arborvitae Turning Brown?

If you are looking for a fast-growing, aesthetically pleasing tree in a vibrant green color, consider arborvitae. Most people plant arborvitae because they are evergreen trees and are great for privacy. Arborvitae grow very quickly, making them ideal for landscaping and as fence borders. As an evergreen, this tree remains green year-round, however, during the cold-weather months, it is common if you notice your arborvitae turning brown. If this happens, there are a few reasons why, such as not enough water, inadequate light, or winter burn. Keep reading to learn why arborvitae foliage turns brown and what you can do to prevent it.

Why Arborvitae Foliage Turns Brown

Browning on arborvitae leaves can occur at various times of the year. The combination of wind, sun, freezing temperatures, and lack of available water in winter can cause arborvitae foliage (and the leaves of other evergreens, as well) to turn brown.

Not Enough Water

Water is the lifeblood of foliage. When brown foliage happens in summer, the color change could be happening because of drought. Make sure that your arborvitae is planted in moist, well-draining soil. If the climate in your area is not providing enough rainfall, you must supplement with water for the shrub, otherwise arborvitae will become stressed.

Insufficient Sunlight

You may notice brown foliage towards the innermost branches of your arborvitae as this is the area most difficult for sunlight to penetrate through. When arborvitae do not receive full sun, they will begin to lose their vibrant green color. They can tolerate shade for a few hours, but thrive when placed in a minimum of six or more hours of direct light per day.

Winter Burn

If your arborvitae shrub turns brown in winter or early spring, the likely reason is winter burn. When an evergreen shrub can't draw water up through its root system to its leaves during periods when the ground is frozen (at which time any moisture in the soil becomes unavailable), those leaves, already beset by challenging conditions, give up their green color and winter burn occurs.

How to Fix an Arborvitae Turning Brown

So how do you prevent arborvitae leaves from turning brown? And if browning does occur during the cold-weather months, what action, if any, should you take once spring returns? Let's begin with five prevention tips:

Protect Against Winter Burn

Regardless of the type of arborvitae you plant, your best bet for avoiding winter burn is to wrap the arborvitae in burlap. Avoid planting arborvitae on the south side of a wall (the sun can be an enemy in winter) or in an area exposed to high winds. Ease up some watering arborvitae in September to encourage hardening off, then maintain adequate irrigation from October until whenever the ground freezes in your area. Such an irrigation regimen will help prepare the shrubs for winter.

Supplemental Watering

Warmer spring and summer weather will also mean more water for arborvitae. Also, look for opportunities to water your arborvitae shrub during the winter. If the ground thaws out at some point in the winter, take advantage. However, snowfall is not enough water for arborvitae. With the soil loose again thanks to the thaw, any water you spray on the ground can permeate down to the plant's root zone once again.

You'll also have to consider how large your arborvitae has grown, as trees as big as six feet tall can use gallons of water. A watering system, moisture meter, and mulch can help to maintain adequate watering for arborvitae. Newly planted arborvitae should be watered daily.

Prune Brown Patches

If arborvitae does not receive enough sunlight, it will not be as full and dense as it usually is. The hardy shrub needs full sun. In this case, you can lightly prune back some of the branches to expose more of the innermost parts of the tree, so it can receive sunlight.

Instead, direct your efforts to prevent winter damage in the future. If green growth does, eventually, re-emerge on a branch damaged by winter burn, prune the branch back as far as that greenery. But if the arborvitae branch never shakes the "brown look," just prune it off entirely. Depending on how severe winters are in your region, you may also have to prune arborvitae because of snow damage. New growth will occur in late spring, so this would be an ideal time to prune. A second seasonal prune can take place in mid-to-late fall.

How to Prevent Arborvitaes From Turning Brown

Although it is a common issue in the shrub, there are some preventative measures you can take to avoid your arborvitae turning brown.

• Fertilize arborvitae at healthy intervals. Arborvitae should be fertilized in the early spring followed by a high-nitrogen fertilizer such as a 20-15-15 or a 10-5-5. As a general rule, you should apply one pound of fertilizer for every 100 square feet of root area.
• Monitoring soil moisture. Arborvitae soil must be consistently moist, so investing in a moisture meter is a great idea to make sure that soil is not overwatered or too dry.
• Checking for pests. Regularly check your tree for pests and diseases, which could contribute to brown foliage. Spider mites, leafminers, and scale are common pests, but you shouldn't have to worry about deer eating your arborvitae as most varieties are not appealing to them.
• Keeping the tree warm. Wrapping the tree in burlap during particularly cold winter weather will help to provide warmth.