There are numerous varieties of day lilies.  Are they all edible?  I have eaten the yellow, purple and pink ones.  Play it safe eat the wild type as seen in this photo.   There are compound flower varieties.  They are a gorgeous garnish or decoration on a plate. (Recipe)

More as an edible wild plant

Day lily salad with chicory leaves, red leaf lettuce, thinly sliced young squash, calendula blossoms, pansies, arugula and borage flowers garnished with bachelor buttons.  For a dressing try a cup of seasoned gourmet rice wine vinegar.  Blend vinegar with a piece (about the size of your little finger) of horse radish root and a clove of garlic.  Add a teaspoon full of lemon thyme blossoms.  (More)
Daylily shoot about to be cut and integrated into a stir fry.  Mild onion like taste.
This double daylily makes an attractive garnish
plopped right into the center of the salad.  Petals may be torn off and tossed in the salad.