How can I get rid of my umbrella grass (papyrus, Cyperus alternifolius) completely? Will glyphosate kill it? Or do I have to dig it out? I've cut it to the ground. It was taking over too much space.
Round up probably would have worked, though you might have needed a second treatment a few weeks later. Unfortunately, now that you've cut it down, you either have to wait for it to regrow (next spring if you're in the northern hemisphere) and treat then with Round up, or dig it all up now. Roundup (and glyphosate) work 'through the green', meaning it needs to be applied to strongly growing, green topgrowth, from where it translocates to the roots and kills the plant over time. In theory, anyway, usually, retreatment is necessary.