Hi, I'm wanting to top some arborvitae, and am wondering if it is safe to do so in February or March.
Malheur County Oregon
The real questio is not when to do this but what the long-term affects on the appearance of the plant will be. Depending on how wide each plant is, and how much you top it, you may create a bare spot without foliage on top of each plant. Arborvitae, like many common conifers, do not produce shoot growth and leaves from these bare stems, so you may find yourself with a hedge composed of plants each of which has a near-permanent bald spot on top. It's always best to trim these back no farther than the foliage extends into the canopy (ie 4-6"). If the bare spot created by the topping is small, the foliage on the perimeter of the spot may grow over time to fill it in, but if it is very large it may never do so. It's probably safe to prune them in any case by the end of March, they are pretty hardy.