Black knot & Elm tree pruning season ends April 1.

Published on Mar 20, 2023

Why can’t I prune into April?

Pruning trees in dormancy can make the job easier as there are no leaves on the branches, so you can see where you are cutting. Pruning the trees also leaves it with an “open wound” where disease can easily enter.

Those April showers that bring May flowers also “awaken” many pathogen spores, and infections often begin in the spring. To reduce the risk of pathogen spread, Prunus trees and Elm trees should not be pruned after April 1.

 How do I prune my tree that has black knot?

  • Prune when plants are dormant (late fall through to early spring) and the knots are easy to see
  • Remove infected branches to at least 15-20 cm (6-8 inches) below the knot.
  • Treat black knot like a hazardous material – clean and disinfect your pruning equipment between every branch and between different trees. Black knot is incredibly infectious.  DISEASED WOOD MUST BE DESTROYED IMMEDIATELY (burned, buried, or removed from site).

What can you do to help prevent DED?

  • Learn to identify an elm tree and recognize the signs and symptoms of DED.
  • Follow best practices to keep your elm trees healthy and less susceptible to DED.
  • Know the laws that prevent DED, and take preventative measures (e.g. don’t transport wood from place to place).
  • Report all suspect infected trees immediately to the StopDED Hotline at 1-877-837-ELMS (3567).
  • Support StopDED by becoming a member.
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