Very interesting. If I had been betting, I would have bet that the peonies would be the no shows, followed closely by the liatris. Daylilies? I've had them live thrown aside on the ground for months! Depending on where in Zone 7 you are, you should definitely be seeing daylilies up. I have some blooming already. (okay. TWO.:)

I have planted and lost liatris three times over the years. I am pretty sure that the culprit is my wet, heavy soil.

Evaluate your growing conditions: was the soil well prepared, loose, and reasonably fertile? Do your plants get at least four to six hours of sun each day? How is the drainage? Daylilies don't demand perfect drainage, but they won't grow in standing water either (as far as I know). How late last fall did you plant them? Did they have time to put out some roots before cold weather set in? Did you mulch the plants? Too much mulch: crown rot? Not enough mulch: freezing? (not likely. All these plants grow much further north than you) Without more info, it's impossible to say what the problem is. It's not entirely too late for them to put in their appearance, but it's getting close.

Another thought: where did these plants come from? If you bought them in the plastic bags with peat around their bare roots, they may have been DOA.

I realize that none of these ideas may be right. It really is a guessing game. Good luck. :)

Patiently for paeonies... it may depend on what was crossed with which to get the varieties you bought.

And they love being fed over summer. Ancient cowpats go down very well... (not in spring or winter in case the plants get attacked by mold.)

But - they don't like to be deeply planted. The growing points need to be only about two inches under the surface.

And they despise being disturbed more than once in any five years or so. Otherwise they sulk.