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Monday - March 15, 2010

From: Houston, TX
Region: Southwest
Topic: Trees
Title: Double trunks on bur oaks in Houston
Answered by: Barbara Medford

QUESTION:

I am involved in a garden club propagation project. One of the trees we have had success propagating is the Bur Oak. Two of these baby Bur Oaks have multi trunks..one has two and the other has three. They both appear healthy and are beautiful specimens. Will these trees be weakened by having more than one trunk? If so, do we prune them now to just having one trunk?

ANSWER:

Quercus macrocarpa (bur oak) is an excellent choice for the Houston area. According to this article from the USDA Forest Service, Bur Oak should be grown from a single leader. From savvygardener.com, we found this article on Pruning Trees, from which we extracted this passage:

"To prune a young tree to a single leader (the stem that will become the trunk), locate the straightest and best leader to retain. In shaping the tree crown, remove lateral branches that are growing upright. They will compete with the leader and form a weak, multi-leader tree. Most trees can be grown with a single leader when they are young, but the growth habit of some species will change to a multiple leader spreading form at maturity. There should be no branches leaving the trunk at an acute angle or narrow forks either between branches or between a branch and the trunk. Branches that are less than two-thirds the diameter of the trunk are less likely to split off than larger branches."

Conditions Comments: The species name macrocarpa refers to the golf ball sized acorns of this tree. The leaves of bur oak also are large, so they are easy to rake. Bur oak is drought resistant, long-lived and reasonably fast-growing for an oak. Tolerates limey soils better than other oaks. Resistant to oak wilt and a number of other problems. Sensitive to root zone disturbance caused by construction.

We would suggest that you do this pruning right away, while the weather is still cool.

Quercus macrocarpa