Source: Rick Durham, extension professor, UK Department of Horticulture

 

Evergreens can be great additions to a landscape, offering interest and splashes of color during winter’s black-and-white palette. They’re also relatively maintenance-free plants.

Three evergreens in particular are often found in the home landscape. Taxus, also known as yews, are popular evergreen shrubs that are often used as foundation plants around a house. Arborvitae’s tall columnar shape work well in groupings that act as screens, and mugo pines are used for their low, spreading habit. Though different in size and texture, all three conifers can exhibit the same types of problems.

If you notice some needles browning or areas of dieback on the evergreens in your yard, there are a number of things that might be causing it. First, it is natural for older needles on evergreens to turn brown and drop off, especially in the fall. But if browning persists, the trouble might come from disease or insect pests. Adverse growing conditions also could be to blame.

This year’s late freezes hit many evergreens just as they were putting out new spring growth. The unseasonably cold temperatures resulted in an array of dead needles at the tips of the branches. Don’t worry. The plants will bounce back, and no permanent damage was done in most cases.

Root damage due to “wet feet” or root rot can both cause needle dieback. Yew, arborvitae and mugo do not like excessive moisture in the ground. Heavy clay soils, sites near downspouts, or overwatering can all lead to unhealthy plants. Before you plant, amend clay soils with organic material to help the soil drain better. If the shrubs are already established and moving them isn’t an option, consider installing French drains or rerouting downspouts to avoid water draining directly into the plant’s root zone. Planting on a high spot is preferable to placing them in a low-lying site.

If you’re seeing dieback on one or more branches, check for physical wounds such as torn bark, partially broken branches or nursery tags that were not removed and might be girdling the branches. Also look for dead, sunken areas on twigs and branches that show yellowing and dieback. Several fungi can cause cankers that girdle branches. In all these instances, prune off dead or damaged branches.

Some evergreens will show damage from spider mites in the summer, though the mites are most active in the cooler spring and fall months. Spider mites feed on the chlorophyll in the needles, causing yellow spots. Shake a branch over a light-colored piece of paper. They are so small, they will appear as tiny, moving dark flecks on the paper. If you see more than 10 mites, you should treat the shrub with a miticide, available at most home-and-garden stores.

Bagworms may also infest evergreens. These caterpillars attach bits of plant material to a cocoon covering their body. When they are small, they move about the tree and feed in late spring and early summer. This is the time they are susceptible to insecticide sprays. Once the bagworms are stationary and the caterpillars pupate in late summer, they no longer feed, and insecticides are ineffective. However, female bagworms will lay several hundred eggs in each bag, so it is a good idea to remove and destroy bags in fall and winter.

For more information about evergreen care, check out extension publication ID-52, What’s Wrong With My Taxus, available online at http://www2.ca.uky.edu/agcomm/pubs/ID/ID52/ID52.pdf, or contact the (COUNTY NAME) office of the University of Kentucky Cooperative Extension Service.

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