Looks like nutgrass.

If you want to get rid of it, it's bad news.

Yes, yellow nutsedge. I just did an internet search re: killing this stuff. This and Canadian thistle are 2 of the hardest weeds to eradicate.

What I found out: Preemergence in late fall early winter with dichlobenil, post-emergence after the plant has 5-6 leaves with Round-Up. The problem is that it can propagate from seeds (least common way), pieces of rhizomes, and from the nutlets that form at the end of the rhizomes. Each nutlet can send up multiple new sedge plants. You have to use post-emergence stuff when the green leaves are big enough to be photosythesizing and re-energizing the nutlet. When the plant is too young, all the movement is from the nutlet to the leaves, and when the plant is very mature, it has formed its own rhizomes and the nutlet is dormant and nothing moves from the leaves to it. When the movement is from the leaves to the nutlet, Round-Up will kill the nutlet.

You can also kill it using landscape fabric to cover it. The tips of the leaves can poke through black plastic. You have to leave the landscape fabric on for at least one whole spring/summer/fall. The nutlets can lay dormant in the soil for a couple of years, but if a plant is sent up to the surface, it will eventually die, along with the nutlet.

It seems like that eradicating this is a multi-year project.