I bought a few Zinnias on sale and they wilt at the smallest attempt to leave them in the sun to get them used to it. Our July sun is pretty hot, often 90's plus. (And maybe their black pots and fast draining soil contribute to it.)Would I be better off putting them in a "Square Foot Garden" that I can cover during high heat and wind, and at night? I mean for a few weeks until they get used to that, and then move them to where I have some Zinnias raised from seed.
Probably on sale because they are root bound maybe? If so, they would be better off in the square foot garden. If they are not root bound, you might try putting them in the shade awhile and make sure they stay moist. If they are root bound, there won't be enough soil left in the pots to hold moisture. Even in the shade, over there the heat alone will dry them out. Not sure if I made any sense.