Annuals live their life through one season. They germinate from seed to flower, develop new seeds and when it frosts they die. While some annuals are able to withstand a bit of frost, most cannot tolerate temperatures that fall below zero. Annuals will bloom more or less non-stop throughout the summer in a full blaze of colour. Unless you germinate your own plants from seed, the investment of buying new potted plants each year can be quite expensive.
Perennials are a more practical choice when looking at cost simply because they grow back each year.
Their roots develop over the course of many seasons, which enables the top growth to increase. The return in perennials comes with time as they begin to spread and fill throughout the garden. Most perennials are hardy enough to withstand northern winters but some tender perennials cannot. Unlike annuals, most bloom for only part of a season. Their foliage collects energy through the rest of the season to strengthen and build the root system.