I have 3 hanging baskets that have never yet looked great. In the past DH (before he was DH) bought pumped-up pots that soon pooped out. Then I took over, but so far haven't done much better. One basket faces south and tends to dry out first, the other two face southeast. There are structures and high trees that obstruct sun part of the time, but hard to judge exactly how much. This summer was hot, hot, hot, and I thought the Avalanch petunias would love it. But noooooo! I put in 2 per planter, along with a Morning Glory, some Bacopa, Lobelia and Alyssum, fertilized with Osmocote, and hired a guy to water once a week while we went away. We were gone from early August to mid-September and very little had changed when we got back. Three little skimpy strings with a handful of blooms at best. Last year Shockwave did slightly better, but not much, or I wouldn't have changed. The other plants did fine, so the pots weren't empty, but there was no wow factor, just a million tiny flowers.
The baskets are 17" wire, lined with sphagnum moss, filled with potting mix and a few water crystals at the bottom. The lobelia and alyssum are poked through the sides of the baskets through the moss so they hang, and I stick in a couple of little plugs on top wherever there's room between the 3 petunias, 2 Bacopas and 1 MG per basket.
Is there a petunia that does better with less light? Or should I try something else entirely? Btw, I grew all the plants from seed, and they were all (except the Alyssum and Lobelia) flowering when planted.