If it were me, I'd dig everything out now and clean off the roots of dirt and weeds as much as I could, put the daylilies in some water in the shade while cleaning the bed of the rest of the weeds, cut the foliage back to about 6 inches from the crown,then replant the daylilies with some new soil. Be sure to replant the daylilies the way it should be done and not buried too deep. You didn't state what zone or state your in so timing is important in completing the task.
That is how I would tackle it . Yes, a big job but better than trying to weed out an overgrown bed where you cannot tell the weeds from the leaves of the daylilies.

Julia

Are you sure they're daylilies? I'm not sure the foliage looks right, and daylilies generally bloom in the summer (at least in my climate). Did you take any photos?

By the way, I had my husband mow a few beds of daylilies that I decided I didn't want. They're still there, but at least I don't have to weed the beds anymore until I have the energy to dig them up.

I agree with maximus - I am thinking they are not daylilies, maybe Siberian Iris? What zone and state are you in?

I was thinking the same thing as twixanddud. When my Siberian iris finish up in the patio surround, they do go over and look just like that. I would determine for sure what plant you're dealing with before determining how to deal with the problem.

Linda