What are these tall prickly plants at the cottage?

Prickly plant

We have tall, prickly plants at our cottage that we can’t seem to kill. Can you tell me what they are and how to get rid of them? They are taking over the other foliage!
—In a Prickle

That’s wild raspberry. (You were likely so frustrated by its pervasiveness that you didn’t recognize it.) And yes, it’s incredibly prolific. If you let it, wild raspberry will simply take over—it’s like a domineering wedding planner.

“It will spread within the boundaries of any suitable habitat if it’s not controlled by some means,” explains Jennifer Doubt, the curator of Botany at the Canadian Museum of Nature. 

The only way to get rid of the stuff for good is to eliminate the entire network of roots. “Dig down and remove everything,” says Hugh Daubeny, a BC-based emeritus research scientist with Agriculture and Agri-Food Canada, who bred raspberries for more than 40 years.

Alternatively, contain the raspberries by surrounding the patch with a metre-deep trench, or by building some kind of structure around them (though Daubeny warns that a wooden box would only work temporarily). Instead, you could just accept the plants’ widespread presence on your property—because, hey, free raspberries!—and regularly prune them. In early spring, cut back tall canes to about 1.5 metres. In the summer, remove the new “suckers” that sprout every few weeks. In the winter, cut out any dried, brown canes. If you maintain them, you can live in harmony with the raspberries. And make a ton of jam.