{"id":2687,"date":"2021-08-19T00:03:35","date_gmt":"2021-08-19T07:03:35","guid":{"rendered":"https:\/\/depts.washington.edu\/hortlib\/pal\/pal-question-475\/"},"modified":"2026-01-12T18:50:52","modified_gmt":"2026-01-13T02:50:52","slug":"thuja-bark-injury","status":"publish","type":"pal","link":"https:\/\/depts.washington.edu\/hortlib\/pal\/thuja-bark-injury\/","title":{"rendered":"Thuja bark injury"},"content":{"rendered":"

I have a mature Western red cedar with an inverted-V gap in the bark,<\/strong>
right at ground level. The point of the V is about 2 ft. off the ground;<\/strong>
the base of the gap is perhaps 9-10″ across. What’s the current thinking on protecting this exposed area from diseases and critters? Paint with some sort of goop? Leave it alone? Or something else?<\/strong><\/p>\n

 <\/p>\n

Here<\/a> is a link to information on managing bark injuries, from
Cornell University’s Plant Disease Diagnostic Clinic, which includes
illustrations. Excerpt:<\/p>\n

“When a split occurs on a tree, what should you do? In recent years,
quite a bit of research has been done on closure of tree wounds. These
investigations have indicated that tree wound paints are of little value
in helping a tree to callus over. For this reason, do not paint or try to
seal a split with paint or tar. Tracing the bark around the split can be
very helpful in aiding wound healing (Fig. 2). With a sharp knife,
starting from one end of the split, trace around one side of the wound,
about 1\/2 to 1 inch back from the split bark. Stop at the other end and
do the same procedure on the opposite side of the split. Knives should be
sterilized between cuts by dipping them for several minutes in a 1:10
bleach:water solution or a 70% alcohol solution to avoid contaminating
the cuts. Carefully remove the bark from inside the traced area. You
should now have a bare area resembling the diagram in Fig. 2. Remember to
leave this untreated. A tree growing with good vigor usually calluses
over quickest. Encourage vigor in the tree with yearly spring fertilizer
applications — and be sure to provide adequate irrigation in hot, dry
weather. Bark splits will often close over completely leaving a slight
ridge in the trunk where callus tissue has been produced.”<\/p>\n

The book Practical Tree Management: An Arborist’s Handbook<\/em> by T. Lawrence
et al. (Inkata Press, 1993) confirms the method described above. Trim
back the bark to healthy tissue around the wound using tools such as a
chisel, gouge, hammer, and sharp knife. Wound margins should be rounded,
and damaged wood within the wound should be smoothed with a chisel or
gouge, but only to the most minimal level (don’t go deep).<\/p>\n

If in doubt, I would recommend contacting a certified arborist for
assistance. You can obtain a referral from Plant Amnesty<\/a>
or the directory of the Pacific Northwest chapter of the International Society of Arboriculture.<\/a><\/p>\n

Thuja plicata<\/a>, <\/span>Trees–Wounds and injuries<\/a><\/div>\n","protected":false},"excerpt":{"rendered":"

I have a mature Western red cedar with an inverted-V gap in the bark,right at ground level. The point of the V is about 2 ft. off the ground;the base of the gap is perhaps 9-10″ across. What’s the current thinking on protecting this exposed area from diseases and critters? Paint with some sort of goop? Leave it alone? Or something else?   Here is a link to information on managing bark injuries, fromCornell University’s Plant Disease Diagnostic Clinic, which…<\/p>\n

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