Black cedar with split bark


Dear Master Gardeners,

About three weeks ago I planted over a hundred three-foot black cedars. Today I noticed that the bark on many of them is split open above ground over a length of about four inches. A different wood is visible in the opening. In many of them, I saw beetle-like bugs (the same kind we often find under rocks around here, along with earthworms). I’ve also noticed that many of my trees have some yellow foliage, but not all the split bark ones are yellow so I don’t know if these “symptoms” are related. I was putting the yellowI g down to transplant shock, the hot weather we’ve had, and my inconsistent watering (which I have now improved with soaker hoses and a timer).

I’ve googled around and could not find answers to my questions. I wonder if the split bark is a concern, if it’s caused by the beetles, and if there is anything I can do. I guess I’d like to know what to expect. I wonder if I should pull out the affect trees to control the pest. I have huge native cedars nearby that I really don’t want to die.

The trees were planted in original clay soil mixed with some triple mix soil. The only soil amendment I made was the addition of supposedly beneficial fungus. I’ve attached a photo showing a split and bug.



Thanks for contacting Toronto Master Gardener.  You don’t have to discard the cedars. Bark splitting can occur for various reasons. For example:

  • Severe cold following by rapid thawing.
  • Late growth in the fall stimulate by warm weather in the fall.
  • Sun scald which can affect or thin barked or young trees.

Trees can create a callus to cover a split.  The best way to encourage the callusing process is to do the following:

  • Trace a half inch to an inch around the split with a sharp knife.
  • Ensure the knife is sterilized in 1:10 bleach or 70% alcohol.
  • Remove the bark inside the traced area.
  • Practice good cultural practices such as adequate watering and fertilization which will help the tree to heal itself.

For more information on treating split bark please see:

Bark splits don’t necessarily kill trees but may make them more susceptible to insect infestation and disease so you need to monitor them closely.  The little creatures on your cedar at this point however are not a big cause for alarm.  They are pillbugs or Armadillidim vulgare.  These are armadillo-like creatures are not insects but belong to the same class of animals as lobsters and shrimps. They need moist conditions to live and feed on decaying organic matter.  They can become a pest if they run out of decaying organic matter to eat because then they start to eat plants but they are not known to target cedars.  For more information on pillbugs please see:

To find out which pests and disease you need to watch out for please see: