Hi, I live in Georgina and have a shady natural wood that now is full of lily-of-the-valley, herb robert, flowering shrubs, some primroses and a lot of garlic mustard and strangling dog vine. How can I control the last 2 pests? I cut them all down as soon as I see them, but I hope there might be a permanent method of keeping them at bay? Spraying was successful. I hope that you can help me, Thanks
Thank you for contacting the Toronto Master Gardeners with your question on invasive weeds.
Well yes these two weeds are indeed difficult to eliminate from your garden, although not equally so.
While Garlic Mustard is possible to eliminate mechanically within one season, the same can not be said for the Dog Strangling Vine.
Dog Strangling vine has deep roots which are near impossible to dig deep enough to get to the network that exists. Unless one is successful at getting all the root, as I am sure you have seen just keeps on returning. The problem is also when we dig down and get part of the root, it stimulates root branching which ends up propagating additional stems. Therefore the best strategy is to be very persistent in just pinching off new shoots as they emerge, and over time this will sap energy and weaken the vines. This is probably not the best news, but it is the best method. If you have an area where you want to eliminate everything mechanically, you can try solorization of soil, but that is probably not practical in your natural shaded setting.
Garlic Mustard is easier to deal with since its roots are not as deep, and is possible to eliminate with mechanical digging or forking. The key I find is timing, when in their lifecycle you attempt to pull them. The two times in their bienniel lifycycle is when they are younger seedlings, or when they throw up their flower spike. When they are younger they are easy to lift with pitch fork. When they are in flower stage, I find hey are easy to just grab by the stem and the root comes out easier at this stage. Once they do become established the problem is if you try to just pull them, they just break off leaving a viable root to reestablish. But even then if you are determined using a pitch fork will work at any stage.
The key is of course with either of these noxious weeds is to make sure they never get to go to seed. If you have any control over your immediate surrounding areas a well, try to eliminate any flowering members.
Enjoy your woodlands !
Further reading on Ontario’s invasive weeds: https://www.invadingspecies.com/plants/