Nutgrass or Nutsedge Difficult to Kill with Chemicals

Q. I have tried digging this weed up but it comes back. I have tried both Roundup and Spectracide according to the package directions, and even painting it on the foliage full strength.

Although it starts out pretty small, if I miss pulling one up, they get quite large. Any assistance in getting rid of this plant is greatly appreciated.

Judging from the roots which actually look like a rhizome I believe this is nutgrass.

A. Judging from the pictures you sent this is one of the nutgrasses or nutsedge. The roots sure look like it to me. To be sure if it is one of the sedges and not a grass, cut the top of the weed off at its stem just below the leaves. Roll the stem between your fingers and see if the stem is triangular rather than round.

            Sedges have triangular stems in cross section. Rolling the stem between your thumb and first finger you should “feel” the triangular bumps of the stem and the stem should not feel round.

Nutgrass with nut attache to the rhizome or "root".

            Sedges, like nutgrass, are more difficult to kill than grasses. Nutgrasses have underground “nuts” attached to the “roots” which are really underground stems called rhizomes. These nuts grow into new plants if they are separated from the mother plant or the mother plant is killed.

            This is why pulling, hoeing or using chemical weed killers do not work on this plant. As you have found out, spraying the tops with Roundup or dandelion killer “burn” the tops back but release the growth of the nuts.

Triangular stem of nutgrass in cross section.

            These nuts are usually anywhere from 4 to 8 inches below the soil surface. All you have done is kill the mother plant and the baby plants released from the nuts that pop from the ground grow like they are on Red Bull. Pulling nutgrass from the soil easily separates the nuts from the mother plant with the same result.

            What to do? There are two basic approaches toward getting some control. The first is soil replacement. If it’s a small area, you can dig down 12 to 14 inches deep, remove the soil and replace it with clean soil. You can take the soil and put it in a clear plastic bag in the middle of summer and “cook” it using the sun.

            You can starve out the nuts. If you continue to remove the tops at the soil surface, over and over, before they get more than two or 3 inches tall it is possible to exhaust or starve the nuts so that they die. If you pursue this option you have got to stay on top of it or it will not work