Dear Toronto Master Gardeners,
I have several, very young weed trees springing up in a spot where they aren’t welcome. I understand I should girdle them to slowly kill them off; this is an interesting technique that is new to me. Should I girdle these trees now (in October)? Will that still be effective? Or should I wait until the spring to girdle? I’m in Toronto.
The best time to girdle a tree would be in the fall after the leaves have been shed. The sap would have returned to the roots of the tree and would be unavailable to “heal” the wound. Make sure that all the bark is removed right down to the phloem (inner-most) layer. Girdling won’t necessarily kill the tree if it is able to produce new shoots from the roots in the spring.
Given the size of the trees in your picture, you may be better off digging up the entire root system (if possible) or even snipping off the tree at ground level to ‘weaken’ it. To do this, remove as much soil as you can around the root system so that you can cut more effectively. In the spring, keep an eye for new growth so that you can deal with it immediately before it grows.