Master Gardener: Planting or replacing evergreens in fall

Jerry Vitalis

There are several reasons why fall is a good time to be adding or replacing evergreens in your landscape. One of the main reasons is that most nurseries and garden centers offer a fine selection of trees and shrubs, including evergreens, at discount prices this time of year. They prefer selling at a reduced price rather than carrying the plants over the winter.

Another reason is that new, tender growth that developed in May and June is tougher by now, and less vulnerable to transplant stress. Also, longer, cooler nights and slowly declining daytime temperatures mean reduced moisture loss through their needles. This, in turn, creates less demand on the plant’s limited root system. Except for the past couple of years, there’s usually ample rainfall, which is another advantage to fall planting.

Be sure to have the people at the nursery or garden center help you plan your landscape so that the trees or shrubs are planted in the best place possible. Two of the problems that we become aware of is planting trees that outgrow the space and the problem of winter burn.

Space becomes a problem when you plant under a window box, next to a window or door, etc; and the tree or shrub must be removed because it outgrows the space.

Winter burn can become a major problem if the right plant is planted in the wrong place.  Winter burn is caused by the sun’s rays heating up evergreen leaves, causing them to transpire. The leaf pores (known as stomata) open, and water vapor exists the leaf.  During warm weather, this water would be replaced by uptake from the plant’s roots.

Landscape evergreens that can be grown in exposed or sunny sites include: black hills spruce, jack pine, mugo pine, ponderosa pine, rocky mountain junipers and eastern red cedar.

When you transplant evergreens, be sure to mulch with three or four inches of shredded bark or wood chips. Spread the mulch over the root area as far as the branches reach or further, but don’t mulch directly against the trunk. Leave a space of at least two inches around the trunk to promote good air circulation.

Since evergreens continue to lose moisture through their needles year-round, it’s doubly important that you don’t allow them to go into winter stressed for moisture. So be sure to water them every two weeks, even more often for newly transplanted evergreens, depending on fall rainfall. Continue watering until the ground is frozen.

— Jerry Vitalis is a Chisago County Master Gardener

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