Hi Lindsay,

This looks like winter burn. Evergreens never really go dormant in winter and desiccating winter winds can dry arborvitae branches out enough that they die back. This is especially true in near-snowless winters, as we had this year. Snow helps protect trees by insulating the ground and roots and we had very little of it this year.

They key to avoiding this is watering in fall right up until the ground freezes. Your site looks exposed and perhaps slopes a little? Even if you have an irrigation system, water these trees well during summer drought and, especially after a dry summer, water them regularly until the ground freezes.

The rust-colored growth is dead. If the dead sections go all the way back to the trunk, that branch is unlikely to come back. If only the tips of branches are dead, you can prune back to green growth and eventually the hole created by pruning will fill with new growth.

These arborvitae look small enough that you could prune the tops off the shrubs with the worst damage. To prevent the plants from sprawling or splitting at the center as they grow, loosely tie the main branches at the top together with soft stretchy material like nylons or a soft wide rope. That will help maintain the shape you want.

The best thing you can do for these is to water regularly.

To maintain their shape, shear arborvitae in May or June with a hedge clipper. Remember never to cut back past green growth on a branch; it will not grow back.

I hope this helps. If you decide you’d rather have a professional prune these plants back, you can find a certified arborist here:

https://www.treesaregood.org/findanarborist

Thanks.

Hi Lindsay,

For normal shearing you wait until new growth begins. With that kind of routine shaping you want to take only an inch or two off the branches to get the best thickest regrowth.

You can prune the tops off and prune out the worst rust-colored sections now. 

Good luck!