Answer: In my experience, planting depth will not usually affect the ultimate height of lilies. Instead, height is most affected by variety planted, the light level available, and the length of time in the ground.
Daylilies (Hemerocallis) can normally grow anywhere from diminutive heights of under one foot to well over five feet depending on the variety selected. By height here I am referring to the height of the flowering stalk or scape. The grassy foliage is usually much shorter in proportion to the scape height. (Five foot high blooms however are rather on the tall side.) If you planted a shorter variety, you may find that it has stretched somewhat if it is growing in less than full open sun.
Daylilies tend to do quite well in heavy clay, although they do appreciate having some organic matter added during the planting process.
The true lilies from bulbs (Lilium) quite often reach five feet, but again depending on variety. If you planted a shorter variety, again it may grow taller if it is in less than full sun; I have also found that bulb lilies tend to be shorter the first year in the garden than in subsequent years. The taller lilies may need to be staked to protect them from blowing over in summer rain storms, especially when they are heavy with bloom.
These lilies also require excellent drainage and may not thrive over time on heavy clay; again the addition of ample organic matter can help things along.
Enjoy your lilies!
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