There is spearmint in a large, sloping border we have. I have dug it out several times and also hacked it back as a quick fix when weather was bad and I was short of time. It comes back every time. There are other lovely plants in the same border meaning I'm not sure I could use weed suppressing membrane without digging out other things, which I'd rather not do. I haven't tried weed killer yet because of the other plants. Does anyone have any suggestions or tips on what to do/use? Leaving it isn't an option as it's become increasingly invasive.