I know little about specialist growing of lilies (I assume you mean "true lilies",
Lilium). The few bulbs I have were planted in the garden in sunny spots with no special treatment and come up and flower every year. I do the same with daylilies. However, for optimum performance daylilies are said to benefit from higher nitrogen than one might think. The only study I found on a quick look for Lilium was that their nitrogen requirements are "moderate".
Lilium are in the plant family Liliaceae. Daylilies (
Hemerocallis) are in the plant family Hemerocallidaceae (or alternatively in the family Xanthorrhoeaceae depending on the authority one goes with - I prefer the former because I don't have to look it up each time I want to spell it correctly
). So they are not closely related although until a few decades ago daylilies were lumped in with the Liliaceae until it was discovered that was inappropriate).
Their growth habit is also different, I wouldn't quite characterize it as shoots coming up first and then foliage developing. The foliage is the first thing to emerge. Leaves do develop along the stem as it grows in lily but not in daylily. They would be photosynthesizing from the time the leaves are sufficiently emerged, they would not be waiting until flowering is finished. They might direct the "food" made by photosynthesis to different places/activities before and after flowering though.
As Cindy said, the size of a daylily plant depends on the cultivar. They range from very small, short plants with small flowers to tall plants with larger flowers. Are you saying that for any given cultivar the plants are smaller and sparser flowering than they should be? Are they in full sun?
