Ask Mr. Smarty Plants

Sadly, nutgrass ranks right up there with poison ivy as gardener's Public Enemy No. 1. First, read this previous answer from Mr. Smarty Plants that pretty well lays out the truth of the matter. As you will note in that answer, herbicides are not really effective because fresh plants will come up from the tubers, deep below. Just yanking at the nutgrass will cause it to break up at soil level, and it will have grown one to two inches by the next day. On the granite path, the problem would be even worse, because the soil will be dry and the nutgrass will easily break and come right back.

The Lady Bird Johnson Wildflower Center recommends neither for nor against pesticides, but the granite paths may be a case where you don't have much choice. However, you will have to use a great deal of caution to keep the spray off your vegetables and perennials. Spray on a still day, keep the sprayer low to the ground, and put some kind of a barrier, like foam board or cardboard between your spraying and the plants you are trying to save. As we said, the nutgrass will come back up, but at least you have a level start. Pull it up, and do your best to get as many tubers as you can.

Now, on the flower and vegetable gardens themselves, we're really sorry, but it's going to have to be pulled out, slowly and carefully, getting as many tubers out as possible. And it's going to have to keep on being done from now on. Nutgrass is very resistant to herbicides, but your other plants are not.

We hope you don't have to go to concrete. And we don't want you to give up gardening. Don't let the nutgrass win!