August 15, 2015

1 - Container grown trees and shrubs from the nursery may be planted in late summer in New Mexico if proper planting and irrigation are provided.

Yard and Garden August 15, 2015

Q.

Is late summer a good time to plant trees from the nursery or should I wait until fall or spring?

A.

Planting trees in the late summer allows gardeners to take advantage of our summer monsoon rains. That, of course, assumes we will have the rain. Even if the rains are insufficient container grown trees from a nursery can be planted if they are properly planted and irrigated.

Bare root trees and shrubs are available only in the spring, so in the summer and autumn you are limited to container grown plants. Plants dug from one site and transplanted to another may have difficulties in the middle of the summer because much of their root systems are removed during transplanting, but container grown tree do not lose much of their root systems and can tolerate summer transplanting more easily. So, container grown trees do have a good chance for successful planting even in the summer.

Proper soil preparation may involve addition of organic matter in the form of compost, but not just in the planting hole. Organic matter should be mixed into a large area around the planting site as if you were preparing a flower bed. This prepared soil should extend several feet from the hole where the tree or shrub will be planted. This facilitates the spread of tree and shrub roots outward into the surrounding soil after planting. Sandy and heavy clay soils benefit most from the addition of compost. If organic amendments are not added to the soil, preparation of the soil still involves digging and loosening the compaction of the soil for several feet outward from the planting hole. Prepare the soil only deeply enough to accommodate the root ball of the container grown plant. Loosening the soil too deeply will cause the tree to sink as the soil settles. This will result in poor tree growth. The base of the root ball should sit on naturally compacted soil and the top of the root ball should be at or slightly above the surface of the surrounding soil. If the root ball is a little high, a layer of mulch will help protect the roots in the upper layers from rapid drying and from rapid temperature changes between day and night.

When planting the new tree or shrub, any circling roots at the edge of the root ball should be cut. This encourages outward growth of roots and reduces chances of circling roots inhibiting growth in the future. Roots extending through drainage holes in the container indicate that circling roots are likely to exist in that particular plant. You may need to cut roots extending through drainage holes to remove the plant from its container.

Fertilizer is not needed the first year or two after planting, but irrigation is especially important. The tree will be establishing its new roots at the new planting site, so moisture is essential. However, a new tree uses less water than older trees because their root systems are limited. As a result, wilting on very hot days may occur. It is important not to create a soggy soil situation. The surface soil will dry quickly, but deeper soil where the roots are developing will dry more slowly. In mid-summer you may need to irrigate once a week. If there is a layer of organic mulch, watering may need to be less frequent. Probe the soil with a long screwdriver or other metal probe periodically to avoid underwatering. When the soil us moist at the depth of the probe, you will feel the coolness of the metal probe. As the soil begins to dry below a few inches, irrigation will be needed. When the tree is first planted, irrigation is needed only at the location of the root ball that was planted, but within weeks the roots should begin to extend outward and the soil should be moistened further outward to facilitate root growth. Roots cannot grow in dry soil.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

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