If it only wilts during midday heat then I wouldn't worry. Some of them are prone to such antics. If it wilted and never sprang back to looking healthy, then I'd gently dig up the tuber and check for rot. But you aren't having that problem.

Now that I think of it, almost ALL my dahlias in the warmest part of the yard wilt in midday heat, and spring back to normal a few hours later. Has it been that warm in the San Fran area?

Poochella,

Thanks for the reply. It has been either warm or raining here in the SF area. I am glad to hear that your dahlias do the same wilting. I guess I can take down the burlap overhang.

Steve