The Q&A Archives: Established Arborvitae Has Competing Leaders

Question: Established Arborvitae, approximately 10 years old, 12 feet high and 4 feet wide at base, healthy in most respects, except that there are two competing leaders. They begin to diverge about 18 inches from the ground; each trunk is about 2 and a half inches in diameter at that point. One of the leaders is slightly stronger and more prominent. They give the tree a split personality that detracts from the optimal shape it should have. I also worry that the two leaders make it more vulnerable to damage when there is heavy snow or ice. Question: Would it be risky to remove the weaker leader at this advanced stage? What's the best time to do it? Will the remaining leader fill out on that side over time? Or would it be safer to live with the two leaders, perhaps lashing them together to improve appearance and minimize risk of damage?

Answer: You have asked a very difficult question and it is hard to answer, especially long distance. If the plant is in a prominent spot in your landscape you might want to consult with a professionally trained arborist before you decide what to do. Lashing is never recommended in the long term because it can constrict the plant's growth and limits its ability to sway and move normally in wind. Removing one of the leaders would result in a very abnormally shaped plant. These plants are not usually pruned that much, but if you do that, cut it in late winter before it begins to grow next spring and follow up to date pruning practices. I would make several observations however. If the plant is healthy, in many respects it may be wisest to leave it alone. Cutting off the second leader would be a rather drastic step; the plant should recover but it might take some years for it to regain a tolerably symmetrical shape. Although these trees are normally fairly symmetrical all on their own, rarely is nature perfectly so -- there is no telling that the regrowth will be an improvement over the current shape. In the long run, you might be better off simply replacing it.

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