Transplanting an old but small tree

Question:

We have a twenty-year-old mimosa tree that is approximately five feet tall and has not begun budding out yet this spring.

I would like to transplant the tree to a different area of the yard. I would like to know if this is advisable and the best way to proceed.

De Baca County

Answer:

It may be difficult to (successfully) transplant such an old mimosa. The fact that it is that old and still so small concerns me. Now, while it is still dormant, is the time to try, however.

As the tree is moved, look to see if the roots have developed well and are not confined to a circle about the size of the original container in which it was grown (if it was purchased as a container-grown tree). If the root system is too confined, it may not be worth moving the tree. You may do better to get a new tree.

However, if the tree is small because it has been grown with little attention, water, and care, it may transplant well. After transplanting, it may grow well if the soil is properly prepared and if it is watered regularly. It may have a deep tap root or "heart roots", but it should not be harmed too severely if these are cut at about two feet deep. The spreading root system near the surface will be the important roots to move. Of course you will cut these roots as well, but dig a relative large diameter root ball (as large as you can possibly manage) when you move it.

Have the new planting site already prepared and the hole waiting when the tree arrives. However, don't prepare the site so far ahead of time that the planting hole will have dried by the time the tree arrives. In preparing the site, rototill a large area (much larger than the root ball that will arrive).

When rototilling add compost (two to four inches over the surface of the area being prepared) to the area, then rototill it into the soil (don't use manure at this time).

Water well to settle the soil after planting (don't physically tamp the soil). Put a mulch over the planting site (at least the area of the root ball) and water two to three times a week for a couple of months, then reduce to once a week through this summer. Next summer water twice a month, this should be the watering schedule for the rest of the life of the tree. At first, water where the root ball was put into the soil and, then begin moving the irrigation away from the trunk to encourage root growth outward. By next year, greatly reduce the watering of the root ball area and water the ring around it. In time, only water from the dripline outward.

Homeowners with a larger tree to move should consider this information, and if possible prune the roots the autumn before transplanting so that a new, more fibrous root system will develop and greatly increase the chances of success. Root pruning means digging a trench about a foot deep around the tree just a little smaller than the diameter of the root ball you will ultimately dig the next year. Make clean cuts (not ragged tears in the roots) as you cut roots when you do this. Fill the trench around the trench with good soil (loosened soil with compost added, or even good potting soil). This will encourage growth of numerous small roots that will more easily establish when the tree is transplanted.

The nice thing about moving a tree from one site to another on your own property is that you have time to do such things. People moving to a new home often do not have such time to plan for moving the trees and shrubs as well. Even with these moves, advance planning increases the chances of success.

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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.

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

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