Answer: Ferns like moist soil and shade. I'd water them deeply once or twice a week, depending upon weather. They will appreciate a top dressing of organic matter (compost, peat, etc.) to slow water evaporation. Use whatever you can find in your garden center.
Using Round-Up on ornamental grasses will kill the tops, but the roots may remain for quite a long time because the chemical isn't translocated to the roots very quickly. The best way to eliminate such plants is to continually cut down the tops. This will eventually starve the roots out (they use energy to develop new sprouts - without photosynthesis to recover the spent energy they will eventually die out). So, keep cutting off anything that sprouts and you'll kill off the root system. Once this happens you should be able to dig out the remaining roots.
Best wishes with your garden renovation project!
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