Hi, welcome to GoY, a lot depends on what species you have, some are annuals, some perennials, and sub shrubs, they're frost tender, but I don't think you need to worry about frost in Florida, so if you have a perennial species, yes they will grow back next year, they won't grow back with aphids, but they may be attacked again, although they won't be the same aphids as this year, you need to use a commercial insecticide spray, preferably a systemic 1, to get rid of them, or introduce species that eat aphids, such as ladybirds, [ladybugs in US A], Derek.

Zinnias are magnets for all kinds of problems. Sooner or later they'll succumb to something. Try to keep them spaced out with good air circulation & deadhead the spent blooms. For aphids, spray with soapy water or vinegar solution; either of these should work - for a while.

Soapy water has always worked for me! How strong did you mix it, Melody, and what happened when you used it?

Agree with Bath. Keep a continual lookout upon them during the growing season for pests so you can take an early intervention if needed.