Brown Arborvitae and Skip Laurels

The 2022-2023 winter season has been challenging for the evergreen plants and trees around the Main Line. I’ve received many phone calls from concerned homeowners asking, “Why are my arborvitae and skip laurels turning brown?”

The reason that evergreen trees and shrubs such as arborvitae, laurels, hollies, spruce, fir and other needled trees have turned brown this winter is due to desiccation. I wrote a previous blog post, Do I Need Anti-Desiccant Spray?, back in November that explains why desiccation (the removal of moisture or drying out) occurs, but I wanted to provide an update now that it is mid-February because so many people have reached out this winter with this exact problem.

We’ve had two significant cold snaps this winter. You might remember the first cold snap occurred right around Christmas. Using Wayne, PA as a point of reference:

December 23rd: High of 57°F, Low of 6°F

December 24th: High of 14°F, Low of 5°F

December 25th: High of 27°F, Low of 14°F

December 26th: High of 28°F, Low of 11°F

By December 30th, exactly one week from the onset of the cold snap, the daily high was back up to 60°F. Emails and calls started coming in about brown shrubs by January 6th.

Next, let’s revisit the more recent cold snap at the beginning of February:

February 3rd: High of 34°F, Low of 13°F

February 4th: High of 26°F, Low of 11°F

Again, six and seven days later we had highs of 60°F and 61°F respectively and customers once again began to call about their brown plants.

You might be thinking, “Isn’t it supposed to be cold in the winter?” Yes, it is supposed to be cold, but the problem is that it’s supposed to stay cold (or at least relatively so).

These wide temperature swings (51° in a single day on December 23rd!), bring trees and shrubs in- and out- of dormancy and cause them to lose water through their evergreen needles or leaves. During the warm, sunny 60°F days, the trees and shrubs lose water through the stomata (like pores in your skin but for plants) that they cannot replace because the ground is still frozen solid. This creates that drying out effect that turns the needles or leaves brown.

So, you’ve looked around your property and noticed a few of your evergreen trees or shrubs show signs of desiccation. Don’t panic - it is unlikely the tree or shrub is completely dead, unless it was already under significant drought stress to begin with. Two things can be done to alleviate desiccation and prevent it from happening next winter.

1. Early season (mid-March to April) plant fertilizing combined with a water-management product, such as Hydretain, that ensures your plant receives and holds on to enough moisture.

2. A late season (December) anti-desiccant spray to prevent further damage next winter.  

In my previous blog post, Do I Need Anti-Desiccant Spray?, I emphasized that the location, exposure, and surrounding landscape can help inform us on whether or not anti-desiccant spray is needed. Although this is still true as every plant and landscape are unique, I am strongly recommending anti-desiccant spray to all customers next year, even if the environmental factors don’t necessarily dictate that it is required. Because these dramatic temperature swings are seemingly becoming normal, I believe anti-desiccant spray will become a really important part of an annual plant health care program.

*Some anti-desiccant manufacturers mix their product with deer spray to protect plants and trees from hungry grazing during the winter months. This is a popular option for customers with deer problems - and let’s face it, we all have a deer problem around here!