Green Scene

Green Scene: It's not too late to plant trees and shrubs

Marginally hardy shrubs and trees such as camellias might need help to get through winter.
Marginally hardy shrubs and trees such as camellias might need help to get through winter. (Sandra Leavitt Lerner For The Washington Post)
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By Joel M. Lerner
Saturday, November 7, 2009

If you thought you had missed your last chance to plant trees or shrubs in your yard this year, think again. November is still a good month to install such plants, as the ground has not frozen yet and the air is still warm enough to work outside.

Almost any kind of tree or shrub will continue to fare well if planted now. That goes for deciduous and hardy broadleaf evergreen plants, as well as spruces, pines and most other conifers. The key to the winter survival of any new plantings, of course, is proper installation.

Begin by preparing the soil where you plan to install the tree or shrub. Till a good-sized area, at least two to three times the width of the root ball, then mix in one part compost with two parts native soil.

Next, dig a hole for the new plant. For a mature tree -- two-inch or larger trunk -- make the hole as deep as the size of the root ball. As the tree or shrub is planted, it should be set on undisturbed or tamped soil in the hole so its doesn't sink later. Be careful not to make the hole too deep; the plant's "root flare," where the trunk meets the roots, should sit a few inches above the soil line.

Of course, as you put the plant in place, its truck should be perpendicular to the horizon and the most attractive side of the plant should face the direction in which it is most likely to be seen.

Before covering the roots of your new plant, you should cut away as much of its burlap wrapper as possible. It's unwise to remove this covering before planting because the root ball may not be sufficiently stable. But leaving all of the burlap in place can pose a risk to the future health of your new plant. That's because much of the burlap in use today has plastic fiber woven into its fabric, which makes it hard for growing roots to expand into the surrounding soil. I've seen numerous trees and shrubs die because their roots became knotted and unable to reach soil outside "plastic" burlap. A good rule of thumb is to cut or fold down the burlap from the top two-thirds of the root ball.

If your new tree or shrub came with the roots secured by wire mesh, bend that wire down under the soil surface and cut through as much burlap as possible. Leave wire baskets on root balls for stability. As these plants grow, baskets will rust. To install trees or shrubs that come in plastic or other types of disposable pots, be sure to remove them completely from those containers. Pull roots from soil if they are tightly woven together, carefully making vertical cuts with a knife in four or five places around the ball.

Once the plant is in place and the roots have been freed from their packaging, it's time to fill the hole with soil mix. Remember to tamp the earth firmly. Don't pile too much soil or mulch around the base of the tree. Doing so can rot bark, increase susceptibility to disease and insects, and interrupt nutrient circulation. The root flare should remain exposed. Feeder roots for many woody plants spread horizontally over a long distance. Except for those with deep taproots, even the largest trees grow, absorb nutrients and are anchored in only the top two feet of soil.

Newly installed plants should be watered immediately with a thorough soaking. Water weekly if there is no rain, throughout the winter if necessary. I recommend that you form a basin around the edge of the root ball to catch rain and irrigation water. Hold off on fertilizing newly installed plants for now, but mulch those new trees and shrubs with two inches of composted leaf mold to hold moisture and protect their roots.

Marginally hardy shrubs and trees, such as camellia, chindo viburnum (V. awabuki 'Chindo'), rosemary, yaupon holly, farkleberry (Vaccinium arboreum) and loropetalum, might need your help to make it through winter. Mulch and burlap wraps work well. Mulch, in the form of leaf mold or other compost, will provide some protection. Locations that shield plants from drying winds and cold temperatures can work well for camellias. Burlap stapled to several stakes surrounding cold-sensitive plants can shield them from harsh winter winds. The bin can be filled with dry leaves, like those from oaks or red maples. This method should protect these fully root hardy, zone 7(8) plants. These extra protective measures are generally not necessary until December. Remove burlap and leaf cover before growth begins in spring.

Most shrubs should not be pruned for shape now. Doing so can stimulate new growth and make plants more susceptible to winter damage. However, pruning taller trees is a common winter job. Remove side branches on the main trunk to raise the tree's canopy to at least six to eight feet above the ground. That way you can see understory plantings and structures. Other necessary pruning practices are removing deadwood and cleaning out inside and crossing branches and suckers. Prune no more than 25 percent of growth. Don't cut the branch collar, a slightly wider area at the base of the branch. Wounds heal faster when this collar is left uncut. Trim away higher branches with a pole pruner. Never use a chainsaw while standing on a ladder. Work that requires climbing should be left to professionals.

Some shrubs I recommend pruning between November and the end of January are butterfly bush (Buddleia davidii) to control seeds, caryopteris when it loses its silver-gray appearance, St. Johns wort when leaves turn brown, and purple beautyberry when its berries are gone or have lost their color.

One final note on tree planting, which brings us back to the importance of site preparation discussed at the beginning of the column: I'm often asked what can be done about roots that run across lawns and cause people to trip. The primary cause for this problem is inadequate site preparation at planting time. Roots grow toward the surface because that's the only place they can find a moist, aerated, well-drained environment. Preparing properly when planting is the only way to avoid this unpleasant outcome.

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md.


© 2009 The Washington Post Company

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