Hi, Doug, : )
Are you using a mulch around the daylilies? This helps conserve moisture and suppress weeds. I tend to buy either a cedar or redwood mulch from Sloat's, and after weeding in April, I spread (or, actually add to existing) mulch and have it at a height of 3-4", but make sure that it's not closer than 2-3" to the daylilies' crowns . There will, of course, be some weeds that sprout in the next 6 months. But they are pretty easy to pull out in a well-mulched area when you walk through the garden and admire your blooms. : )
Since you live in the city, I would imagine that you don't have a huge problem with weed seeds that are wind borne from Open Space. There are products (e.g., Preen) that prevent weed seeds from sprouting. But, these pre-emergents don't deal with existing weeds. They simply have to be pulled out - preferably when the soil is moist.
Please, ask questions when needed! Happy gardening! : ) - Elizabete