A perennial is any plant that lives for more than two years. This distinguishes them from Annuals which complete their life cycle in one year (typically in one growing season) and biennials which usually grow only vegetation the first year and then flower the second year before dying. All garden plants including trees and shrubs are categorized as either woody or herbaceous and gardeners discuss the latter in terms of Annuals, Biennials and Perennials.

Nature has come up with two clever ways to allow plants the best possibility of reproducing. Annuals such as Begonias , Zinnias and Nasturtiums have one growing season to germinate, grow, pollinate, set seed and then die. With such a busy schedule, these plants devote maximum energy into producing high numbers of smaller seeds so that perhaps a few of them will become next year's plants. Perennials typically grow year after year and don't have such a hurried schedule. They simply produce new growth on last year's woody stems, or store enough energy in root structures such as bulbs to produce new stems each year. On average, perennials devote more resources to fewer, larger seeds than annuals. This typically yields a higher percentage of seeds which will successfully germinate. With less worry about survival, perennials often take time to get established and may not produce flowers for a few or even many years. Once established though, perennials will often produce beautiful flowers year after year. One side note, there are a group of perennials called "monocarpic" that will only bloom once and then die. The Agave is a good example of this.

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Perennials are generally considered hardier than annuals because they can survive more extreme conditions. They typically produce the most complicated root structures which give them better access to scarce nutrients in nutrient poor soils, better protection from extreme temperatures and even protection from wildfires. This is why so many native prairie plants are perennials. They are found in greater abundance in very cold and very dry conditions and display remarkable adaptations which allow them to survive for many years before successfully reproducing.

Growers have given us a myriad of perennials to choose from. Your local garden center carries the most tried and true species and cultivars that grow well in your area. One thing to remember is that although a plant may be a perennial, it may not behave like one in your garden. Some perennials just can't make it though harsh winters and must be replanted each year. Others will not survive through the hot summers in the South. Luckily, growers are always developing new hardy perennial varieties for gardeners who live in these areas. Check with your garden center.