1 - Conifers respond to pruning in a manner different from the response of deciduous trees, so cutting the top of a conifer to use as a Christmas tree may not result in regrowth and an attractive tree that is left behind.

Yard and Garden December 13, 2014

Q.

If I cut the top from my overgrown arbor vitae tree to use as a Christmas tree, will it regrow?

A.

An arbor vitae or most other conifer trees will probably not regrow a new trunk if the main leader (trunk) is cut. In some cases where the main trunk of a conifer is broken or damaged by wind, ice, or other factors close enough to the top, it may develop a new leader, but if it is cut far enough from the top, it is unlikely to develop a new trunk.

I recently saw something that made me think of your question in a different manner than I would have otherwise. I saw arbor vitae trees at the corners of a residential lot that had been topped at a height of about 4 feet. As I walked up, the plants looked quite nice. From up close I looked into the center of the plants and noticed no green in the center. Barren grey branches and twigs were all that were apparent. There was no regrowth in the central portion. However, unless you were looking at the plant from above, it was not apparent. From the side, the plant was still aesthetically pleasing. If you do something like this for your trees, but prune high enough, you may be able to "have your cake and eat it too". Just cut it high enough so that the old, non-regenerating center is not visible and you will be left with a green shrub-like plant that looks OK from ground level.

Many years ago I heard a lecturer say that "conifers are difficult to prune because they will not regrow when cut back into brown (or gray) older branches". This is a mostly true statement. Pruning conifers is different from pruning deciduous and broadleaf evergreen trees. Deciduous and many broadleaf evergreen trees have dormant buds that readily sprout from a large branch or trunk behind a pruning cut or breakage from environmental factors. Conifers are much less likely to produce new growth from older wood. If the arbor vitae tree is overgrown horizontally as well as vertically, you must consider this information when pruning the branches. Prune them to leave some young, green growth at the ends. These younger growths can regenerate new growth and not leave a barren appearance. If this is not possible, another option is to cut the overgrown tree, use it for decoration purposes, and replace it with a new tree or shrub. You can also use the site of the old tree to create a flower bed since there will be little growth of grass in that location. You will have old, slow to decompose roots with which to contend. You can leave most of them there to slowly decompose, only removing those that are in the way of planting, or you can try removing the trunk and old roots if you wish.

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.

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