Planting in Containers
Unlike garden plants that require much effort and timing to be moved, plants in containers can be rearranged as easily as the furniture in your living room. If one container is having a "bad hair day" it can be moved to a less conspicuous spot to recover and replaced with something more appealing. Containers are also a way of having plants where there isn't any natural ground, or having plants that you don't necessarily want to leave behind when you move.
Keep in mind when using containers that they NEED TO BE WATERED REGULARLY. Even plants that don't need to be watered in the ground must be watered in containers. The air circulating around the pot wicks the moisture out of the soil inside. Containers that are glazed on the outside or inside stay moist longer than containers that are porous. And the larger the container and volume of soil the better it will hold moisture. Window boxes are notorious plant killers - up in the air with air all around and usually quite small. They work well in Holland where it rains all the time but not so well in California where we have 8 months of drought.
Potting soil is designed to drain well and hold it's structure and is good to use. If you want to add some top soil for better water retention you can either mix it with the potting soil or put 3 or 4 inches of potting soil in the bottom of the container and around the edges and use top soil in the middle. Top soil by itself quickly becomes too compacted for plants. And no matter how good your potting soil, you still need to take out the plants and replace the soil every few years. We use a nine month slow release fertilizer in our containers, it's easy and works well. Your garden center is probably filled with other choices, just make sure they're designed for containers.
There aren't any rules for what you can and can't use. Be outrageous. If something dies consider it an opportunity to try something else. We've listed some of our favorites below, ones that look good most of the year. The small container plants stay fairly small but of course can be planted in larger containers as well. You can put just one plant in your container and watch it grow or you can cram it full of plants and play survival of the fittest.