Keep several things in mind when choosing plants to grow on a patio or deck. First, find a plant that won't outgrow your patio. If you don't want to spend a lot of time caring for your patio garden, choose plants that don't require consistently moist soil. Then take into consideration the amount of light your patio gets per day. If it sits in the sun all day you have a wider choice of plants than if you have a shady patio. If choosing flowering plants, choose those with staggered blooming times so that you have continuous color all season.
Lily of the Nile
The agapanthus, or Lily of the Nile, is primarily grown in pots in areas that get full sun in the morning. If you plant the rhizome in the spring you will have blooms all summer long, in your choice of blue or white flowers. This plant needs well-draining soil, as do most potted plants. Very easy to grow, the Lily of the Nile is hardy to USDA Zones 8a to 11.
For early spring color on your patio, plant pansies. These little flowers are hardy to USDA Zones 7a to 10b, and bloom in a wide range of colors and mixtures of colors. They like full sun but will do well with afternoon shade. The pansy does require moist soil and dead-heading in order to keep blooming. Dead-heading is the process of removing older, dead or dying flowers so that the plant won't go to seed and stop blooming.
If you want to add some greenery to the patio, consider the asparagus fern. Hardy to USDA Zones 9a to 11, this plant needs to be watered when the surface of the soil is dry. They don't do well in cold temperatures, so plan to add it to your houseplant collection during the winter.
For a truly low-maintenance patio plant, choose the coleus. Because of it's attractive foliage it will add both greenery and color to the patio. This plant likes filtered sunlight and will even do well in a somewhat shady location. If it begins to wilt, water it and it will perk right up. Not a very cold-hardy plant, this is one you may one to bring indoors before the first frost. Coleus is hardy to USDA Zones 9a to 11.