Supertunia® Pretty Much Picasso® (Petunia)

From Proven Winners website (some editing done):
Maintenance Notes:
Self-cleaning no deadheading necessary.

Late July and August is when plants should be at their best, but there is only one problem: The plants have run out of energy and the gardeners realize it too late to help the plants recover. This is especially true in raised containers and hanging baskets. Here is the best way to keep your Petunias in the Super category.

1. When you buy them in the spring, buy a slow release fertilizer to top dress the basket or container.

2. In May fertilize with a water-soluble fertilizer once every two weeks.

3. In June as the weather starts to get warm to hot, fertilize weekly, again with a good soaking. If the weather turns really hot as it sometimes does in Late June you may need to fertilize every third watering. By now the Supertunia is really growing and starting to tumble down from the basket or fill out across the flowerbed.

4. July is when the cutting back occurs. Around the 4th of July, re-apply slow release fertilizer. At the same time, trim back
some of the longer branches just enough to bring the plant back in line with the bottom of the pot or basket. Don't remove too much at the maximum cut back 20% of the branches or 1 in five shoots. You can also just give it a general light trim. Your plant will be out of flower for a few days, but will come back stronger than ever. By now with July's heat you should be watering at least every other day and begin to fertilize every other watering.

5. August is, hot, humid,

I like this opinion