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posted: 11/8/2013 1:00 AM

Don't forget evergreens need water, even in the cold

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  • Thoroughly water evergreens planted in the last three years so they will not lose too much moisture in freezing temperatures.

    Thoroughly water evergreens planted in the last three years so they will not lose too much moisture in freezing temperatures.

By Tim Johnson
Chicago Botanic Garden

It is easy to forget about watering during the colder weather in November. However, evergreens planted over the previous three years should be watered this month if conditions are dry. Recently planted evergreens should not go into winter under drought stress, which will increase the chance of winter burn.

Evergreens cannot take up moisture from frozen soil, so in freezing temperatures with drying winds they can lose moisture from their leaves faster than the roots can replace it.

Make sure the root balls of evergreen trees and shrubs are thoroughly moistened when watering by applying water right at the base of the plant. Water from rain or a sprinkler may not reach the roots, because densely branched evergreens can shed water away from the roots.

Have your garden soil tested to determine how best to manage it and what fertilizers to use next year. Make a composite sample from a few areas in the bed and send in for testing. If your garden is large, it is a good idea to divide the garden into zones and test them separately.

Soils in the Chicago area tend to have adequate phosphorus levels, so in these situations choose fertilizers that contain little or no phosphorus. A soil test will confirm the status of your garden soil.

Wait to cut back perennials with attractive dried foliage until early spring so that there will be some winter interest in the garden. Some perennials, such as hostas, will not look good after being frozen, so it is best to cut them back in fall as they flatten to the ground. As a general rule, cut back the plants that do not look good late in the fall and the remaining plants in early spring.

You may want to consider cutting more perennials back in the fall if you have had problems with voles. Voles are compact rodents with stocky bodies, short legs and short tails and can be mistaken for mice. They do not hibernate and are active throughout the year, mostly at dawn and dusk.

Voles primarily eat the stems and leaves of various grasses, but they also consume other vegetation. They will eat the bark of trees and shrubs during the winter, which is typically the most serious damage they do.

Gardens with low-lying landscaping, such as arborvitae, spreading yews, junipers and cranberry cotoneaster, have higher potential for vole activity because the plants hide the voles from predators such as hawks and owls. In general, removing cover is very effective in preventing vole damage.

Voles are the most prolific when they can hide in abundant vegetation. The damage is likely to be more severe during extended cold spells with deep snow cover because voles can tunnel through the snow.

Eliminate weeds and dense ground cover around lawns to give less cover to voles. Mow lawns and other turf regularly, and cut back vegetation from the bases of trees and shrubs as winter approaches in areas where there is vole activity.

Also, it is a good idea to pull mulch back away from the base of trees and shrubs and keep the snow cleared away from the base of young trees.

• Tim Johnson is director of horticulture at Chicago Botanic Garden,

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