Why Are My Emerald Cedar Leaves Turning Brown?

Browning on Arborvitae Branch Tips a Serious Problem

Arborvitae shrub
Kimberly Frost Photography / Getty Images

Emerald cedar (arborvitae) is a commonly used tall shrub or small tree that works well for creating screens and borders. Unfortunately, some homeowners who plant emerald cedar experience the problem of its leaves turn brown. Drought is usually the source of the issue, but sometimes insects, diseases, or even dog urine can be the culprits.

Brown Foliage Location and Causes

When you see dead foliage on the inner part of emerald cedars, it's generally not a problem. It's normal to see brown leaves in this area in fall or spring, as the emerald cedars are shedding foliage.

But leaves turning brown at the outer tips of branches can be a serious problem. If you see such brown leaves in the summer, it could be due to any of the following, or some combination thereof:

  1. Aphids: Inspect foliage closely for masses of these tiny, soft-bodied insects that can be orange, green, black, or brown. Specialized sprays are available to treat aphids, and you can also try some DIY options.
  2. Spider mites: Check the tree for tiny spiders that are usually red, brown, or yellow. You may also be able to see some tiny webbing. You can try using insecticidal soap on spider mites, but sometimes once they're identified, the problem is too advanced to cure.
  3. Fungal diseases: Look for tiny black spots on the foliage in summer. If you see them, remove infected branches to prevent further spread. If the problem persists, have your local garden center recommend an antifungal spray.
  4. Drought: If you inspect the brown leaves and don't see any spots or bugs, you can assume your trees are not getting enough water.

Irrigation Techniques

If drought is what's making your leaves brown, you can supply artificial irrigation and bark mulch. For established plants, a deep soaking every other week is sometimes recommended. Of course, this does not address the issue of vegetation that has already been damaged by drought. In severe cases, root damage can occur, resulting in dead plants. To check to see if your plant is dead or still alive, slice off a bit of bark with a knife. If you see green, the plant is probably living (on a partially dead plant, it may take you a few tries before you find green somewhere). If all that you find is brown, the plant is most likely dead, and you should start making plans to remove and replace it.

Dog Urine

Just one of many examples of the challenges we face in landscaping with dogs, urine spraying can be detrimental to plants. Your emerald cedar's foliage may have turned brown because it has been sprayed with dog urine. If your own dog is the culprit, you can try creating a separate fenced-in area to let them run free, or opt to use a leash when taking them out. If there's a stray dog problem in your neighborhood, you can try to deter them with dog repellents.

Article Sources
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  1. Emerald Green Arborvitae. University of Washington Website