A biennial plant is a flowering plant that, generally in a temperate climate, takes two years to complete its biological life cycle. [1] [2]
In its first year, the biennial plant undergoes primary growth, during which its vegetative structures (leaves, stems, and roots) develop. Usually, the stem of the plant remains short and the leaves are low to the ground, forming a rosette. After one year's growing season, the plant enters a period of dormancy for the colder months. Many biennials require a cold treatment, or vernalization before they will flower. [3] During the next spring or summer, the stem of the biennial plant elongates greatly, or "bolts". [4] The plant then flowers, producing fruits and seeds before it finally dies. There are far fewer biennials than either perennial plants or annual plants. [5]
Biennials do not always follow a strict two-year life cycle and the majority of plants in the wild can take 3 or more years to fully mature. Rosette leaf size has been found to predict when a plant may enter its second stage of flowering and seed production. [6] Alternatively, under extreme climatic conditions, a biennial plant may complete its life cycle rapidly (e.g., in three months instead of two years). [7] This is quite common in vegetable or flower seedlings that were vernalized before they were planted in the ground. This behavior leads to many normally biennial plants being treated as annuals in some areas. Conversely, an annual grown under extremely favorable conditions may have highly successful seed propagation, giving it the appearance of being biennial or perennial. Some short-lived perennials may appear to be biennial rather than perennial. True biennials flower only once, while many perennials will flower every year once mature.
Biennials grown for flowers, fruits, or seeds are grown for two years, whereas those grown for edible leaves or roots are harvested after one year—and are not kept a second year to run to seed.
Examples of biennial plants are members of the onion family including leek, [4] some members of the cabbage family, [4] common mullein, parsley, fennel, [4] Lunaria , silverbeet, black-eyed Susan, sweet William, colic weed, carrot, [4] and some hollyhocks. Plant breeders have produced annual cultivars of several biennials that will flower the first year from seed, for example, foxglove and stock.
An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. Globally, only 6% of all plant species and 13% of herbaceous plants are annuals. The annual life cycle has independently emerged in over 120 different plant families throughout the entire angiosperm phylogeny.
Lettuce is an annual plant of the family Asteraceae. It is most often grown as a leaf vegetable, but sometimes for its stem and seeds. Lettuce is most often used for salads, although it is also seen in other kinds of food, such as soups, sandwiches and wraps; it can also be grilled. One variety, celtuce, is grown for its stems, which are eaten either raw or cooked. In addition to its main use as a leafy green, it has also gathered religious and medicinal significance over centuries of human consumption. Europe and North America originally dominated the market for lettuce, but by the late 20th century the consumption of lettuce had spread throughout the world. As of 2021, world production of lettuce and chicory was 27 million tonnes, 53 percent of which came from China.
Vernalization is the induction of a plant's flowering process by exposure to the prolonged cold of winter, or by an artificial equivalent. After vernalization, plants have acquired the ability to flower, but they may require additional seasonal cues or weeks of growth before they will actually do so. The term is sometimes used to refer to the need of herbal (non-woody) plants for a period of cold dormancy in order to produce new shoots and leaves, but this usage is discouraged.
The parsnip is a root vegetable closely related to carrot and parsley, all belonging to the flowering plant family Apiaceae. It is a biennial plant usually grown as an annual. Its long taproot has cream-colored skin and flesh, and, left in the ground to mature, becomes sweeter in flavor after winter frosts. In its first growing season, the plant has a rosette of pinnate, mid-green leaves. If unharvested, it produces a flowering stem topped by an umbel of small yellow flowers in its second growing season, later producing pale brown, flat, winged seeds. By this time, the stem has become woody, and the tap root inedible. Precautions should be taken when handling the stems and foliage, as parsnip sap can cause a skin rash or even blindness if exposed to sunlight after handling.
Onopordum acanthium is a flowering plant in the family Asteraceae. It is native to Europe and Western Asia from the Iberian Peninsula east to Kazakhstan, and north to central Scandinavia, and widely naturalised elsewhere, with especially large populations present in the United States and Australia. It is a vigorous biennial plant with coarse, spiny leaves and conspicuous spiny-winged stems.
The Marantaceae are a family, the arrowroot family, of flowering plants consisting of 31 genera and around 530 species, defining it as one of the most species-rich families in its order. Species of this family are found in lowland tropical forests of Africa, Asia, and the Americas. The majority (80%) of the species are found in the American tropics, followed by Asian (11%) and African (9%) tropics. They are commonly called the prayer-plant family and are also known for their unique secondary pollination presentation.
A perennial plant or simply perennial is a plant that lives more than two years. The term is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also widely used to distinguish plants with little or no woody growth from trees and shrubs, which are also technically perennials. Notably, it is estimated that 94% of plant species fall under the category of perennials, underscoring the prevalence of plants with lifespans exceeding two years in the botanical world
Safflower is a highly branched, herbaceous, thistle-like annual plant in the family Asteraceae. It is commercially cultivated for vegetable oil extracted from the seeds and was used by the early Spanish colonies along the Rio Grande as a substitute for saffron. Plants are 30 to 150 cm tall with globular flower heads having yellow, orange, or red flowers. Each branch will usually have from one to five flower heads containing 15 to 20 seeds per head. Safflower is native to arid environments having seasonal rain. It grows a deep taproot which enables it to thrive in such environments.
Capsicum annuum is a fruiting plant from the family Solanaceae (nightshades), within the genus Capsicum which is native to northern region of South America, and southwestern North America. The plant produces berries of many colors including red, green, and yellow, often with pungent taste. It also has many varieties and common names including paprika, chili pepper, jalapeño, cayenne, bell pepper, and many more with over 200 variations within the species. It is also one of the oldest cultivated crops, with domestication dating back to around 6,000 years ago in regions of Mexico. The genus Capsicum has over 30 species but Capsicum annuum is the primary species in its genus, as it has been widely cultivated for human consumption for a substantial amount of time and has spread across the world. This species has many uses in culinary applications, medicinal uses, self defense, and can even be ornamental. With high levels of cultivation the species is cared for greatly and globaly, though there are still some pests and diseases that can impact the species.
Oenothera biennis, the common evening-primrose, is a species of flowering plant in the family Onagraceae, native to eastern and central North America, from Newfoundland west to Alberta, southeast to Florida, and southwest to Texas, and widely naturalized elsewhere in temperate and subtropical regions. Evening primrose oil is produced from the plant.
Dianthus armeria, the Deptford pink or grass pink, is a species of Dianthus ("pink") native to most of Europe, from Portugal north to southern Scotland and southern Finland, and east to Ukraine and the Caucasus. It is naturalised in North America.
Lepidium campestre, the field pepperwort, field peppercress, field peppergrass, field pepperweed or field cress, is usually a biennial with some form of annual plant in the Brassicaceae or mustard family, native to Europe, but commonly found in North America as an invasive weed. The most notable characteristic of field pepperweed is the raceme of flowers which forks off of the stem. These racemes are made up of first small white flowers and later green, flat and oval seedpods each about 6 mm long and 4 mm wide. Each seedpod contains two brown, 2.5 mm long seeds.
Moringa oleifera is a fast-growing, drought-resistant tree of the family Moringaceae, native to the Indian subcontinent and used extensively in South and Southeast Asia. Common names include moringa, drumstick tree, horseradish tree, or malunggay.
Mesembryanthemum crystallinum is a prostrate succulent plant native to Africa, Sinai and southern Europe, and naturalized in the New World. The plant is covered with large, glistening bladder cells or water vesicles, reflected in its common names of common ice plant, crystalline ice plant or ice plant.
Chaerophyllum bulbosum is a species of flowering plant from the carrot family and known by several common names, including turnip-rooted chervil, tuberous-rooted chervil, bulbous chervil, and parsnip chervil. It is native to Europe and Western Asia. It was a popular vegetable in the 19th century.
Abortion in flowers and developing fruits is a common occurrence in plants.
In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal purposes, or for fragrances. Culinary use typically distinguishes herbs from spices. Herbs generally refers to the leafy green or flowering parts of a plant, while spices are usually dried and produced from other parts of the plant, including seeds, bark, roots and fruits.
Torilis japonica, the erect hedgeparsley, upright hedge-parsley or Japanese hedge parsley, is a herbaceous flowering plant species in the celery family Apiaceae. Japanese hedge parsley is considered both an annual and biennial plant depending on the biogeographical location. This means Japanese hedge parsley can complete its life cycle in either one or two growing seasons depending on habitat. Japanese hedge parsley is typically found in areas with disturbed soils, pastures, margins, open woodland, near waste sites, or right-of-way habitats. It can withstand a variety of habitats, thriving in partial and full shaded areas, but also withstanding habitats with full sunlight penetration. It is considered an aggressive invasive species in North America; invading a wide range of habitats due to its environmental tolerance and tendency to outcompete native vegetation. This species is considered a threat in several areas that causes problems relating to overall environmental health and stability. Aside from its environmental implications, T. japonica has potential to fight several cancers through a terpene it produces called Torilin, extracted from its fruits.
Oxera splendida is an evergreen vine in the family Lamiaceae which produces white, fragrant flowers and white, egg-shaped fruit. It naturally is occurs in the tropical rain forests of tropical Asia and Australia and is often sighted along rain forest margins such as roads. Some common names include October Glory, Glory Vine, Potato Vine and Fragrant Faradaya. Australian indigenous names include Garanggal used from Cairns to Yarrabah, Buku used in the Tully River area, Koie-yan used at Dunk Island and Djungeen used by the Girramay clan.
Annuality and perenniality represent major life history strategies within plant lineages. These traits can shift from one to another over both macroevolutionary and microevolutionary timescales. While perenniality and annuality are often described as discrete either-or traits, they often occur in a continuous spectrum. The complex history of switches between annual and perennial habit involve both natural and artificial causes, and studies of this fluctuation have importance to sustainable agriculture.