Perennials

Perennials are plants that live for more than two years. Typically the term perennial is used for herbaceous perennials where the top dies back during the winter. Although the term is not frequently used for them in gardening, shrubs and trees are also perennials. Most perennial plants flower more than once. Some perennials flower reasonably quickly, whereas for others the gardener may have to wait more than a year. 
One example of perennial that is not herbaceous is the Wallflower. Technically, it is a sub shrub growing woody stems that can live for several years. 
Plants that are perennials in one climate may behave as annuals in another climate. Morning Glory is an example of this. In Australia and the Southern United States, Morning Glory is a perennial and constitutes a serious weed. In Britain, Morning Glory always dies during the winter and is considered a valued garden plant, not a weed. The related bindweed is a nasty perennial weed in the UK. 
Perennials tend to survive well in wild habitats. Many highly popular garden plants are perennials as are many troublesome weeds. 
==See also==
*Annuals