What turns a potted plant into a container garden? Some folks consider a combination of plants in a container to be a designed container garden. Others feel container gardens are groupings of containers. It's a fine distinction and as with all things related to garden design, the final decision is up to you.
What can you grow in a container? Just about any plant that you can grow in the ground. You can use one season annuals or long-lived trees. It's also a great place to play with plants that aren't hardy in your area, since you can always move them indoors at the end of the season.
Then there's the choice of pots. Container gardening may well be the biggest venue for your gardening creativity. Here are some ideas to get you started.