check the labels on Image for Nutsedge and on Vantage weed chemicals

You can lay down landscaping cloth/weed cloth around the plants and top with gravel or bark.

You can use Round-up Herbicide in a wick applicator available at most home & garden centers. Google wick application of herbicides to better understand how the process works. Us a pre-emergent herbicide like Preen or SnapShot to help prevent weed seed germination. Follow label instructions for proper use.