1. Calibrachoa or Million Bells
If I could only pick one container garden plant to grow (though I shudder to think of that), it would probably be calibrachoa, also known as million bells. This plant comes in about a million spectacular colors that range from pure white to different shades of pink to deep purple.
Calibrachoa look great in almost any container garden. The prolific blossoms attract hummingbirds and butterflies and will go strong all summer with regular feeding.
Calibrachoas don't need deadheading but they do need consistent watering and good drainage - no soggy roots for these guys.
Verbena is a great container garden plant for sun because it will flower like crazy all summer long and into the fall. It plays well with others - looking good by filling in spaces and spilling over edges with it's densely clustered blossoms.
There are many colors of verbena to choose from - brilliant red to deep, dark blue. These profuse bloomers are extremely forgiving. They are drought tolerant and only need an average amount of water. They do need good drainage and like most flowering annuals, verbenas need to be fed every couple of weeks. Though deadheading isn't necessary for most common varieties, your plant will look much better if cut it back when blooms fade.
Verbenas are great for attracting butterflies.
3. Cape Daisy or Osteospermum
My first container gardens were pots filled with cape daisies or ostiospermum. I bought them in early spring and they survived several frosts - winning my undying love.
These plants are cheerful, forgiving (they are hardy to 25 degrees)and come in a variety of and handsome colors from a deep pink to melon, purple and white. My favorite is "Orange Symphony."
Though the tags say no deadheading is necessary, the plants certainly will look better if you do. Fertilize regularly, make sure they have good drainage and they will last well into fall. If they start getting leggy, cut way back.