Annuals must be set out or seeded every year since they don't persist. Some varieties will self-sow, or naturally reseed themselves. This may be undesirable in most flowers because the parents of this seed are unknown and hybrid characteristics will be lost. Plants will scatter everywhere instead of their designated spot. Examples are alyssum, petunia, and impatiens.
Annuals have many positive features.
They are versatile, sturdy, and relatively cheap. Plant breeders have produced many new and improved varieties. Annuals are easy to grow, produce instant color, and most important, they bloom for most of the growing season. 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.