COLUMBIA Mo.—Just because July has arrived, there is no need to stop planting trees and shrubs, said University of Missouri Extension horticulturist David Trinklein.
Early spring and late fall are the traditional times for planting woody ornamentals. “However, with the development of different methods of growing nursery stock and modern transplanting equipment, planting at other times is possible and may be quite desirable,” said Trinklein.
Nursery stock is available as balled-and-burlapped, container-grown or bare-rooted. Nursery stock that has been field-grown, dug, then balled and burlap wrapped may be planted into the landscape at any time. Although there is some root loss when the trees or shrubs are dug, modern practices such as root pruning in the field help to force roots to grow in the ball of soil that will be dug, thus easing transplanting shock.
Container-grown plants also are candidates for planting at any time of the year. All the roots currently supporting the growth of the tree or shrub are in the container. Therefore, transplant shock is minimal if properly planted and watered.
But planting bare-root trees and shrubs during the summer is not advisable, since digging them for sale destroys a large portion of their root system, Trinklein said. The extensive root damage makes it hard for plants to absorb enough water to survive intense summer heat. “Planting them during winter dormancy is preferred.”
When planting trees and shrubs, dig a wide, shallow planting hole. Most trees exhibit dense root growth from 5 to 15 inches below the soil surface. Anchoring roots are mainly at a depth of 3 feet, although actual depth varies with density and aeration of the surrounding soil.
Root systems do not mirror the top growth of a tree or shrub; they often grow much wider than the top growth but not nearly as deep. The outline of the shoot and root system of a mature tree or shrub looks more like a water goblet than an hourglass. Therefore, a wide, shallow hole is preferred rather than a narrow, deep one that may be only slightly wider than the soil ball (or nursery container) around the roots being planted.
Improve the planting area by adding organic matter. However, it should become a transitional area between the existing growing medium around the roots and the native soil in the area. Allow the edges of the planting area to remain rough and irregular. A smooth wall of tight clay at the edge of a planting hole makes it difficult for young roots to penetrate, and they may begin to grow in a circle within the hole.
Do not plant trees or shrubs deeper than they have been growing. Ideally, plant slightly shallower to allow for settling. Organic matter will gradually decompose in the soil ball as well as the surrounding improved area. The native soil and mulch materials will gradually settle in to replace it, and native soil will become the main growing medium.
If it is hot and dry when planting, mist the tree or shrub leaves during the hottest part of the day to ease stress. If the plant is small, a shade screen of some sort can help during the first few weeks of establishment or until cooler weather returns.
To establish strong roots, newly planted trees need deep, slow watering directly at the root zone. Keep new roots moist, but not overwatered, since they are delicate and can easily suffocate with too much watering. Mulch applied over the planting area lessens watering frequency and keeps the soil around the plant cooler and in better condition.
Prune trees and shrubs when they are planted. Remove injured or poorly placed branches, as well as branches with narrow angles with the trunk. Remove lower branches gradually, never limbing up more than one-third of the way up the trunk in any given year.
“With the natural form of plant in mind, envision the types of cuts that might be made to encourage the plant to grow in an aesthetically pleasing way into the space provided for it,” Trinklein said.
For more information, the MU Extension publication “How To Plant a Tree” is available free online at https://extension.missouri.edu/publications/g6850.
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