Perennial plants live for two years or more. Perennials differ from annuals and biennials with annuals replanted every year and biennials every other year. Perennial’s that bloom during spring and summer will die back in autumn, rest during the winter, then re-grow the following spring from the existing root-stock; these are also known as deciduous perennials. If the climate is continually warm, a perennial will continually grow and produce flowers and or fruit. A perennial relocated from its native habitat may become an annual in another region requiring planting by seed or propagation. Perennials can also vary between long-lived and short-lived varieties.
Perennials produce structures such as bulbs, tubers, rhizomes, corms, stolons, as well as woody crowns. These structures keep the plant thriving from one year to the next during cold weather dormancy or drought and produce new growth from existing plant tissue. Annuals produce a new generation through the production of seeds that lay over during the cold months, ready to grow again once the conditions are right. Some perennials may not flower or set fruit for several years if the conditions are not right. There are perennials that may also produce seeds like the annuals. Perennials place their roots deep in the soil layer protecting them from potential wildfires.
Class of Perennials
Evergreens are non-herbaceous perennials, meaning they retain their leaves all year long, such as furs and pines. Herbaceous perennials include potato, peony, hosta, mint, most ferns and most grasses. Herbaceous perennials can tolerate extreme conditions such as the arctic winters and wildfires due to the root’s protection below ground in the soil layer. This same root system can also prevent soil erosion and help retain the dissolved nitrogen preventing it from contaminating any surface water. The perennial root system will also block the growth of weeds, which in turn lessens the need for herbicides.
Subshrubs retain a woody structure during winter such as trees, shrubs and vines. Monocarpics are plants that set flower and fruit once before dying. Perennials that flower and set fruit over many seasons are termed polycarpic.
Perennial plants survive in ecosystems where no other plant can. Perennials can be found on land, in fresh water, and some in shallow seawater. Most plants found on the tundra, prairies or above the timberline are perennials, surviving where no other plant can.
Image Caption: Perennial Dahlia. Credit: Uwe H. Friese (Vulkan)/Wikipedia (CC BY 3.0, 2.5, 2.0 and 1.0)