There are a few disadvantages to annuals. They must be set out as plants or sowed from seed every year, which involves some effort and expense. Old flower heads should be removed on a weekly basis to ensure continuous bloom. If they are not removed, the plants will produce seed, complete their life cycle, and die. Many annuals begin to look disreputable by late summer and need to be cut back for regrowth or replaced.
Annuals offer the gardener a chance to experiment with color, height, texture, and form.
If a mistake is made, it's only for one growing season. Culture and maintenance of annuals Site Selection. Consider aspects of the site that affect plant growth such as light, soil characteristics, and topography. Different annuals perform well in full sun, light shade, or heavy shade. The slope of the site will affect temperature and drainage.