In some ways, this looks like quackgrass. A photo of the rhizomes would be helpful.
Look at the perennial grasses in our Weed Gallery: https://extension.umd.edu/hgic/topics/lawn-weed-id-and-management
Never let it go to seed, as then you'll have it everywhere. You can apply a herbicide formulated for grasses only, that will not affect your broad-leaved plants. Or, you can apply a total vegetation killer (usually has glyphosate) and use a shield of cardboard or plastic to keep it from contacting your desirable plants.