Cedar hedge is dying


I am hoping you can help.
I live in Eas York and planted a cedar hedge last year on the East and North Borders of my property.
About 3 weeks ago I applied a new layer of mulch (about an inch and half deep) and following the recent heavy rain quite a few of the trees have started to turn brown and also black on the branches.
In late June I also applied a cedar hedge fertilizer to the soil and was also planning to apply again at the end me of
I removed much of the layer of mulch in the last week, as I read that the roots may not be able to breath with all the rain, but the trees continue to turn a light brown at the ends of the branches.
The trees in the attached photo are between 5 and 7 feet high and on the east side of my property.
I would appreciate any advice you can provide on how to revive the trees and ensure the other trees don’t also begin to turn brown/black as well
Many thanks
Jeremy Gibbs


Thank you for your inquiry about what might be causing the browning of your cedars (Arborvitae).

There may be several issues: moisture, fertilizer, light. However, the main cause, as you seem to suspect, may be too much moisture due to the added layer of mulch compounded by the rainfall. Do you have clay or sandy soil; if it’s clay, the soil would not be able to absorb more water; the mulch would retain the moisture, possibly suffocating the roots and causing root rot, which would cause the branches to brown.  Generally, using a mulch is an excellent way to help to retain moisture as long as the soil is not waterlogged. Water when the top few inches feel dry, but make sure that the soil is not dry and that the water is able to penetrate to the roots.

Was there any browning by the end of the growing season? That might indicate that they were planted too deeply? Did they have ample water before the ground froze?

You mention that you’ve applied a “cedar hedge fertilizer”, perhaps with the intention of correcting the browning problem. Actually, one does not need to add any soil amendments or fertilizers until the transplants are more established and the roots have had time to grow. Once established, using a layer of compost, leaf or otherwise, would supply much of the nutrients that the cedars would need to remain healthy.

Are the plants getting sufficient sun? Not sure when you took the picture; cedars require full sun to grow well; it looks quite shady in general, but the picture may have been taken late in the day when the sun was setting.

We hope that some of these suggestions will help your cedars to recover.

July 26, 2021