Perennial plant

"Perennial" redirects here. For other uses, see Perennial (disambiguation).

Flower of common chicory, a perennial plant

A perennial plant or simply perennial (Latin per, "through", annus, "year") is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials. More correctly, woody plants like shrubs and trees are also perennials.

Perennials, especially small flowering plants, grow and bloom over the spring and summer and then die back every autumn and winter, then return in the spring from their root-stock rather than seeding themselves as an annual plant does. These are known as herbaceous perennials. However, depending on the rigors of local climate, a plant that is a perennial in its native habitat, or in a milder garden, may be treated by a gardener as an annual and planted out every year, from seed, from cuttings or from divisions.

The symbol for a perennial plant, based on Species Plantarum by Linnaeus, is , which is also the astronomical symbol for the planet Jupiter.

Life cycle

Perennial plants can be short-lived (only a few years) or they can be long-lived, as are some woody plants like trees which can live for over 4,000 years. They can vary in height from only a few millimeters to over 100 meters tall. They include a wide assortment of plant groups from ferns and liverworts to the highly diverse flowering plants like orchids and grasses.

Plants that flower and fruit only once and then die are termed monocarpic or semelparous. However, most perennials are polycarpic, flowering over many seasons in their lifetime.

Structure

Perennials typically grow structures that allow them to adapt to living from one year to the next through a form of vegetative reproduction rather than seeding. These structures include bulbs, tubers, woody crowns, rhizomes plus others. They might have specialized stems or crowns that allow them to survive periods of dormancy over cold or dry seasons during the year. Annuals produce seeds to continue the species as a new generation while the growing season is suitable, and the seeds survive over the cold or dry period to begin growth when the conditions are again suitable.

Many perennials, in contrast, have specialized to survive under extreme environmental conditions: some have adapted to survive hot and dry conditions, or to survive under cold temperatures. Those plants tend to invest a lot of resource into their adaptations and often do not flower and set seed until after a few years of growth. Many perennials produce relatively large seeds, which can have an advantage, with larger seedlings produced after germination that can better compete with other plants or more quickly develop leaves for photosynthesis. Annuals tend to produce many more seeds per plant since they will die at the end of the growing season, while perennials are not under the same pressure to produce large numbers of seeds but can produce seeds over many years.

The dahlia is a perennial.

Growth

In warmer and more favorable climates, perennials grow continuously. In seasonal climates, their growth is limited to the growing season. For example, in temperate regions a perennial plant may grow and bloom during the warm part of the year, with the foliage dying back in the winter. These plants are deciduous perennials. Regrowth is from existing stem tissue. In many parts of the world, seasonality is expressed as wet and dry periods rather than warm and cold periods. In some species, perennials retain their foliage all year round; these are evergreen perennials.

With their roots protected below ground in the soil layer, perennial plants are notably tolerant of wildfire. Herbaceous perennials are also able to tolerate the extremes of cold in temperate and Arctic winters, with less sensitivity than trees or shrubs.

Knowing the planting zone can be very useful when you are planning your garden and flower bed areas. Gardeners should compare their garden climates with the climate where a plant is known to grow well. Most plants are marked with a zone number which corresponds with a region on a map where that plant will survive. While a range of zones might be listed, the lower of the zone numbers indicates the lowest recommended zone in which that plant can survive. It is possible that a plant might thrive outside a labeled zone area.

Benefits in agriculture

Switchgrass is a deep-rooted perennial. These roots are more than 3 meters long.

Although most of humanity is fed by seeds from annual grain crops, perennial crops provide numerous benefits. Perennial plants often have deep, extensive root systems which can hold soil to prevent erosion, capture dissolved nitrogen before it can contaminate ground and surface water, and outcompete weeds (reducing the need for herbicides). These potential benefits of perennials have resulted in new attempts to increase the seed yield of perennial species, which could result in the creation of new perennial grain crops. Some examples of new perennial crops being developed are perennial rice and intermediate wheatgrass.

Location

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Right frame

Parallel view

Cross-eye view

Seeds from various perennial flowers.

Perennial plants dominate many natural ecosystems on land and in fresh water, with only a very few (e.g. Zostera) occurring in shallow sea water. Herbaceous perennial plants are particularly dominant in conditions too fire-prone for trees and shrubs, e.g., most plants on prairies and steppes are perennials; they are also dominant on tundra too cold for tree growth. Nearly all forest plants are perennials, including the trees and shrubs.

Perennial plants are usually better competitors than annual plants, especially under stable, resource-poor conditions. This is due to the development of larger root systems which can access water and soil nutrients deeper in the soil and to earlier emergence in the spring.

Types

• Examples of evergreen perennials include Begonia and banana.
• Examples of deciduous perennials include goldenrod and mint.
• Examples of monocarpic perennials include Agave and some species of Streptocarpus.
• Examples of woody perennials include maple, pine, and apple trees.
• Examples of herbaceous perennials used in agriculture include alfalfa, Thinopyrum intermedium, and Red clover.

Perennial fruits

• Apple
• Apricot
• Avocado
• Banana - Technically a herb.
• Blackcurrant
• Blueberry
• Currant
• Feijoa
• Grape
• Kiwi Fruit
• Japanese Wineberry
• Pear
• Persimmon
• Pineapple
• Plum
• Raspberries
• Strawberry
• Strawberry Tree

Perennial herbs

• Agastache
• Alfalfa
• Basil, many varieties: African Blue, East Indian
• Chives
• Dill
• Fennel
• Ferula
• Garlic
• Ginger
• Hops -Humulus

• Horseradish
• Lavender
• Lemon Balm
• Mint
• Onions, many varieties: Potato onions, Shallots, Egyptian onions, Japanese bunching onions, Welsh onions, Chinese leeks
• Oregano
• Piper nigrum (black pepper)
• Rosemary
• Sage
• Thyme
• Valerian
• White Horehound -Marrubium vulgare
• Yarrow (Achillea millefolium)

Perennial vegetables

• Allium tricoccum: commonly known as ramps, spring onion, ramson, wild leek, or ail des bois
• Asparagus
• Broccoli: Nine Star
• Chicory
• Chives
• Colocasia esculenta
• Eggplant
• Globe artichoke
• Ground Nut (Apios americana)
• Hog nut
• Jerusalem Artichoke
• Konjac
• Lamb's quarter
• Leek
• Milkweed (Asclepias)
• Okra
• Potato
• Radicchio or a.k.a. Italian Chicory
• Rhubarb
• Shallot
• Siberian Pea Tree (Caragana arborescens)
• Sorrel
• Rakkyo
• Sea Kale
• Spinach varieties: Ceylon Spinach, Sissoo Spinach, New Zealand Spinach
• Sweet potato
• Taro
• Watercress

See also

• Annual plant
• Biennial plant
• Herbchronology
• Herbaceous
• Perennial grain

External links

• USDA Plant Hardiness Zone Map
• Gardening with Perennials
• Edible Aroids
• Plants for a Future