Answer: Since you'll be tilling the area, you'll be exposing the roots of all the weeds and grasses, making them easy to pull. Be sure to rake all the roots out before leveling the area and planting your bulbs so you can avoid surprises sprouting up in your bulb bed. There are several tactics you can employ to keep bermuda grass from invading the bed. A metal or plastic barrier around the outside of your bed will keep the stolons from creeping into the bed; a sharp spade run around the edge of the bed every few weeks will sever any stolons trying to invade; a 3-4" layer of organic mulch will make bermuda grass easy to pull out if it creeps into the bed; a weed cloth barrier on the soil surface (under the mulch) will keep burmuda grass from rooting in the bed.
Best wishes with your daylilies (and your bermuda grass)!
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