Please, Do NOT Prune Your Elm Trees Until October

By: albertaarb - April 29, 2015

Do you have elm trees? Do you want to keep them? Keep reading.

Dutch Elm Disease is devastating to our beloved elm trees, having claimed million of elm trees since arriving here from Europe in the 1930s. But it’s effects are entirely preventable. Start by waiting to prune your trees.

According to, the disease is “spread by both a native and an introduced bark beetle whose larvae tunnel under the outer bark and create distinctive feeding 'galleries.'”

The city of Calgary has asked that residents don’t prune these trees until October, to prevent the spread of the disease carrying beetles.

Here’s how you can do your trees and your neighbours’ trees a big favour.

Fighting Dutch Elm Disease

According to the City of Calgary, area residents should:

  • Adhere to the Provincial elm pruning ban between April 1 and September 30. Pruning should be done when beetles are not active, between October and March. All tools used on diseased trees should be disinfected. So do not prune elm trees. 

  • Elm materials should be disposed of at City landfills – stored elm firewood is an ideal breeding ground for elm bark beetles.

  • All trees should be watered every two to three weeks from April to mid-August, then again in the fall before freezing. Trees need much more water than lawns do. 

How to Spot Dutch Elm Disease

Aside from waiting to prune elm trees, you can also do your part by finding the signs of this disease and reporting it to city officials right away.

Here’s what to look for:

  1. Your leaves will wilt, turn yellow, then brown (also called flagging) on multiple branches on your tree

  2. Yellow leaves may drop off prematurely. However, the brown ones may stay stuck to branches through the winter months.

  3. First signs usually manifesting in June.

How the City is Fighting Dutch Elm Disease

This disease poses a serious risk to our province’s trees, and it’s something the city of Calgary takes very seriously.

According to the City, “The City takes several steps to prevent introduction of Dutch elm disease to Alberta, including promoting elm health, promoting awareness of the disease, monitoring elm beetle populations and testing trees for DED symptoms.”

“Sticky panel traps with lures are placed at sites throughout Calgary and checked every 30 days during the summer to monitor beetle populations.”

Anyone looking to report an infected tree, or with more questions are encouraged to call 1-877-837-ELMS, or visit

Do You Need Tree Pruning Services?

At Alberta Arborists, we offer tree pruning services to Alberta residents. Our professionally trained arborists can properly prune your trees & shrubs in order to remove dead, dying, diseased or damaged limbs, increase light & air penetration by selective thinning and also eliminate potential hazards.

Contact us today for a free, no-obligation estimate of your job, and save your money and time.

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