I've been struggling for years to manage a wild raspberry bush patch that's out of control, measuring about 30 feet by 20 feet. I'm fed up! I'm thinking of cutting them down and laying cardboard over the area, like I've seen people do to suppress weeds. Will this method be effective? Should I also add a thin layer of mulch on top of the cardboard? I want to avoid raising the height of my yard, and unfortunately, I can't dig them up due to the roots of several large trees in the vicinity. I'm located in Ontario, Canada. What are your thoughts or personal experiences with this?
3 Answers
I've read that cardboard alone might not be super effective. Some folks suggest adding a black tarp to help solarize the area when it's really hot. If you really want to suppress those raspberries, you might need to pile on at least 6 inches of wood chips on top of the cardboard. Good luck!
Using double-thick cardboard, like those banana boxes, along with about a 3-inch layer of wood chips on top could work well. If you ask around, you might find an arborist willing to drop some wood chips for you for free; it can really help smother those stubborn plants.
I eventually just gave in and used brushwood killer for my raspberries. It did the trick! I couldn't dig them out since they were wedged between fences. Personally, I doubt just cardboard will cut it; those plants can be pretty persistent. If you're looking for a more definitive solution, that might be the way to go.
I took down some invasive blackberries by cutting them back to about 8 inches, painting the cut ends with brush killer, and wrapping them tight with a plastic bag to keep the poison contained. It worked like a charm without harming my other plants!