Waves are my favorite because of the extremely short internodes - they're easy to keep compact; but I sometimes have trouble finding the 'waves'.
Petunias are perennials, which means they are capable of living for more than 2 growth cycles, but they are very short-lived - usually 2-3 years is all you can get out of them, which raises the question, is it worth it? Well, that's for you to decide.
You could try to over-winter by pruning them back and keeping them in a bright window or under lights, but the better way would be to withhold water and allow them to dry down before you move them to a cool dark place which will force then into a consequential dormancy. If you have an attached garage, you could probably put the plants in their pot up against the wall between house/garage and cover them with an over-turned cardboard box. The box will capture geothermal heat rising through the floor as well as conductive heat from inside the home. You might need to provide a bit of water every month or so, depending on a number of factors, so they don't dry out entirely. The later strategy is easy and will leave you with a more robust plant come spring. about 6-8 weeks before your last frost date, bare-root and repot into fresh soil, keeping it slightly moist until you see new growth. After the repotting, they will need good light to keep them compact. I use Foliage-Pro 9-3-6 fertilizer for all my mixed plantings.
Al
