About 94 percent of plant species are perennials, not annuals
Gardeners think of annuals as the norm, but an estimated 94 percent of plant species live longer than two years. Some wait decades to bloom: a century plant can live 80 years and reach 30 metres before flowering once and dying. Most perennials, though, flower season after season from roots they keep.
Botanically, a perennial is simply a plant that survives beyond two years, as opposed to annuals that finish in one growing season and biennials that need two. The word is also used loosely for soft-stemmed plants, even though trees and shrubs technically qualify too. Herbaceous perennials die back above ground each autumn and return in spring from their rootstock, while evergreen kinds such as Bergenia keep their leaves all year, and subshrubs like Penstemon hold on to a little woody framework through winter.
Staying alive between seasons takes investment. Perennials put more resources than annuals into roots, crowns, bulbs, tubers, rhizomes and similar organs that store carbohydrates through cold or dry dormancy, then fuel fresh growth. That head start lets them leaf out earlier and grow taller, capturing more light and space. Deep roots also reach water and nutrients further down, which is why perennials tend to win in stable, poor conditions, while fast-breeding annuals do better where ground is frequently disturbed. Underground buds and thick cork help some species survive wildfires.
Where a plant counts as perennial can depend on climate. Tomatoes live for several years in their tropical and subtropical homes but are grown as annuals in temperate gardens because their foliage cannot survive winter. In places where seasons swing between wet and dry rather than warm and cold, deciduous perennials drop leaves in the dry months. Perennials dominate prairies, steppes and tundra and make up nearly all forest plants, though very few, such as eelgrass, grow in shallow seawater.
Farming may borrow these traits. Most people are fed by annual grains resown every year, but perennial crops can hold soil against erosion, trap nitrogen before it pollutes water and crowd out weeds. Breeders are developing perennial rice and intermediate wheatgrass, sold as Kernza; one perennial rice from 2018 matched replanted annual rice over eight straight harvests, according to a 2023 report. Gardeners already spend heavily on them: potted herbaceous perennials sold in the United States in 2019 were worth more than 900 million dollars.
Source: Perennial
