These include several which have resulted from both chance and deliberate hybridisation. In addition, breeding work in Europe and Australia has produced annual forms with an outstanding range of colours - yellow, red, purple, orange. These are excellent for a massed, colourful display. Most forms are suited to cultivation in many areas. The annual forms can be purchased in packets from a number of commercial suppliers and established as instructed on the packs.
Perennial forms are usually quick growing in a sunny, well drained position.
They benefit from a regular light pruning annually to encourage branching and a greater number of flowers. They respond well to annual fertilising, usually with a slow-release type and appreciate an assured water supply. The plants vary in their ability to withstand frost but most are at least moderately frost resistant. Propagation from cuttings is also fairly easy and is the only way that named cultivars should be propagated. You may have reached this description from one of several different sources.