When I was a kid, the daylilies I was familiar with were the tall orange naturalized kind that you sometimes see on roadsides in the country. Even though some people consider them weeds (and they can indeed get out of hand), there are some of those in my north yard. But for many years, I have been interesting in acquiring a range of hybrid hemerocallis in a variety of colors.
One of the neat innovations that the hybridizers (and the daylilies themselves, of course) have come up with is a contrasting color at the center of the bloom that is different from the throat color or the color of the rest of the petals. I especially like the purple and white ones.
As the name suggests, each individual flower blooms for only one day. But during the blooming season there are lots of flowers coming on each day and mature plants can have plenty of blooms still open while others have already closed. Sometimes I go around and pick off the finished blooms (it's neater and maybe is better for the plants?), but you can always see a few.
Some hybrids have ruffled edges, like fancy pie pastry. The foliage is full and makes a good covering to discourage weeds from growing in a line of daylilies. They are often planted with daffodils so that the daylily foliage is starting up just when the daffodil foliage has flopped over and isn't so attractive. We have done this along our east and south fences. So we have blooms there in April and May from the daffs and in July and August from the daylilies.
Some daylilies are fragrant, but others are not. It depends on the hybrid. There are very tall ones too, ones that do well in hot weather in the South, and miniatures (the flowers are smaller and more delicate, but the plants aren't miniature). The "tet hems" (tetrapoloid versus diploid) have an extra chromosome; many of those kinds have very large flowers with thick petals. There are some that bloom earlier in the season and some that are quite late. A well-known cultivar called "Stella d'Oro," a short yellow daylily, is often used in public places for its reliability, easy care, and long period of bloom.
Although collecting new hybrids and prize-winning named cultivars of daylilies can be an expensive (but popular) hobby, many lovely daylilies are available at garden centers for reasonable prices. Also, there are gardeners who actually do what the books suggest -- divide their perennials periodically. So I have bought daylily divisions at private plant sales. One year a very kind woman with a great many beautiful daylilies gave me starts from a half dozen of her plants.
Along the outside of the fence on the east side of our house, we have a line of herbaceous peonies with daylilies just in front of them. The foliage of the now-finished peonies makes a nice backdrop for this charming lemon yellow hemerocallis.
For a number of years when my husband and I were able to garden actively by ourselves, we were adding new flower beds each spring, and we would take a trip up to a place just south of Madison, Wisconsin, called The Flower Factory. They have a wonderful range of interesting perennials and the plants were always in beautiful condition and reasonably priced. We'd fill our van and go back home and plant them. One year when we unloaded the van, we discovered half a dozen pots of this bright yellow and red so-called "spider" daylily that we hadn't purchased. It turned out to be a very nice gift or accident -- we don't know which :)