Portuguese
cyperus rotundus 
A widely distributed perennial sedge having small edible nutlike tubers.
1
Gardeners who allow purple nutsedge to go unchecked will find that it not only has taken over but also poisons other plants.
2
But what makes purple nutsedge particularly vicious is its ability to release allelopathic compounds into the soil, which actually kill the competition.
1
There is a grass called nut grass, and another called Parramatta grass, either of which holds its own against anything living or dead.