An escaped plant is a cultivated plant that has escaped from agriculture, forestry or garden cultivation and has become naturalized in the wild. Usually not native to an area, escaped plants may become invasive. [2] Therefore, escaped plants are the subject of research in invasion biology. [3]
Some ornamental plants have characteristics which allow them to escape cultivation and become weedy in alien ecosystems with far-reaching ecological and economic consequences. Escaped garden plants may be called garden escapes [4] or escaped ornamentals. [5] Sometimes, their origins can even be traced back to botanical gardens.
All escaped plants belong to the so-called hemerochoric plants. This term is used across the board for plants that have been introduced directly or indirectly by humans. The term also includes the unintentionally introduced plants that were introduced through seed pollution (speirochoric) or through unintentional transport (agochoric). [6]
Plants may escape from cultivation in various ways, including the dumping of green waste in bushland and road reserves and by birds or other animals eating the fruits or seeds and dispersing them. [7] Others are accidental hitchhikers that escape on ships, vehicles, and equipment. [8] Plants can also escape through sending stolons (runners), as stolons are capable of independent growth in other areas. [9] Garden escapees can be adventive, which means they can be established by human influence in a site outside their area of origin. [10] Some plants, such as the opium poppy Papaver somniferum , [11] : 93 escaped from cultivation so long ago that they are considered archaeophytes, and their original source may be obscure. [11] : 1123
Occasionally, seed contamination also introduces new plants that could reproduce for a short period of time. The proportion of adventitious species in open ruderal corridors at such locations can exceed 30% of the flora of these locations. Further, ornamental alien plants can easily escape their confined areas (such as gardens and greenhouses) and naturalize if the climate outside changes to their benefit. [12] In the US, there are over 5,000 escaped plants, many of which are escaped ornamentals. [13]
Many invasive neophytes in Australia and New Zealand were originally garden escapees. The Jerusalem thorn forms impenetrable thorny thickets in the Northern Territory which can be several kilometers in length and width. Two other plants introduced as ornamental garden plants, Asparagus asparagoides and Chrysanthemoides monilifera , now dominate the herbaceous layer in many eucalyptus forests and supplant perennials, grasses, orchids, and lilies. [14]
Neophytes that compete aggressively, and which displace and repel populations of native species, may permanently change the habitat for native species and can become an economic problem. For example, species of Opuntia (prickly pears) have been introduced from America to Australia, and have become wild, thus rendering territories unsuitable for breeding[ clarification needed ]; the same goes for European gorse (Ulex europaeus) in New Zealand. [15]
Rhododendron species introduced as ornamental garden plants in the British Isles crowd out island vegetation. [16] The same can be seen in many acidic peatlands in the Atlantic and subatlantic climates. Robinia pseudoacacia was imported from America to Central Europe for its rapid growth, and it now threatens the scarce steppe and natural forest areas of the drylands. Examples in forests include Prunus serotina which was initially introduced to speed up the accumulation of humus.
In North America, Tamarisk trees, native to southern Europe and temperate parts of Asia, have proven to be problematic plants. In nutrient-poor heaths, but rich in grasses and bushes (fynbos) in the region Cape in South Africa, species of eucalyptus from Australia are growing strongly. As they are largely accustomed to poor soils, and in the Cape region they lack competitors for nutrients and parasites that could regulate their population, they are able to greatly modify the biotope. In Hawaii, the epiphytic fern Phlebodium aureum , native to the tropical Americas, has spread widely and is considered an invasive plant. [17]
Particularly unstable ecosystems, already unbalanced by attacks or possessing certain characteristics, can be further damaged by escaped plants if the vegetation is already weakened. In the humid forests of Australia, escaped plants first colonize along roads and paths and then enter the interior of the regions they surround. [18]
Thunbergia mysorensis , native to India, invaded the rainforests around the coastal city of Cairns in Queensland and even invades trees 40 m high. In Central Australia, the Eurasian species Tamarix aphylla grows along river banks, repelling native tree species, and wildlife that go together, lowers water levels and increases soil salinity. As in the United States, tamarisks have proven to be formidable bio-invaders. The fight against this species of trees, which has spread widely since, appears to be almost hopeless. [19] [20]
Escaped plants can fall within the definition of, and may have a relation to, these botanical terminologies below:
Examples of escaped plants and/or garden escapees include:
A wildlife garden is an environment created with the purpose to serve as a sustainable haven for surrounding wildlife. Wildlife gardens contain a variety of habitats that cater to native and local plants, birds, amphibians, reptiles, insects, mammals and so on, and are meant to sustain locally native flora and fauna. Other names this type of gardening goes by can vary, prominent ones being habitat, ecology, and conservation gardening.
An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there by human activity, directly or indirectly, and either deliberately or accidentally. Non-native species can have various effects on the local ecosystem. Introduced species that become established and spread beyond the place of introduction are considered naturalized. The process of human-caused introduction is distinguished from biological colonization, in which species spread to new areas through "natural" (non-human) means such as storms and rafting. The Latin expression neobiota captures the characteristic that these species are new biota to their environment in terms of established biological network relationships. Neobiota can further be divided into neozoa and neophyta (plants).
The genus Tamarix is composed of about 50–60 species of flowering plants in the family Tamaricaceae, native to drier areas of Eurasia and Africa. The generic name originated in Latin and may refer to the Tamaris River in Hispania Tarraconensis (Spain).
Impatiens glandulifera, Himalayan balsam, is a large annual plant native to the Himalayas. Via human introduction it is now present across much of the Northern Hemisphere and is considered an invasive species in many areas. Uprooting or cutting the plants is an effective means of control.
Cenchrus setaceus, commonly known as crimson fountaingrass, is a C4 perennial bunch grass that is native to open, scrubby habitats in East Africa, tropical Africa, the Middle East and south-western Asia. It has been introduced to many parts of the world as an ornamental plant, and has become an invasive species in some of them. It is drought-tolerant, grows fast, reaches 3 feet in height, and has many purple, plumose flower spikes.
A synanthrope is an organism that lives near and benefits from humans and their environmental modifications. The term synanthrope includes many species regarded as pests or weeds, but does not include domesticated animals. Common synanthrope habitats include houses, gardens, farms, parks, roadsides and rubbish dumps.
Naturalisation is the ecological phenomenon through which a species, taxon, or population of exotic origin integrates into a given ecosystem, becoming capable of reproducing and growing in it, and proceeds to disseminate spontaneously. In some instances, the presence of a species in a given ecosystem is so ancient that it cannot be presupposed whether it is native or introduced.
The need for a clearly defined and consistent invasion biology terminology has been acknowledged by many sources. Invasive species, or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats. Invasion biology is the study of these organisms and the processes of species invasion.
A cultigen or cultivated plant is a plant that has been deliberately altered or selected by humans. These plants have commercial value in horticulture, agriculture or forestry. They are defined by their mode of origin and not by where they grow. Plants meeting this definition remain cultigens whether they are naturalised, deliberately planted in the wild, or grown in cultivation.
Lathyrus aphaca, known as the yellow pea or yellow vetchling, is an annual species in the family Fabaceae with yellow flowers and solitary, pea-like fruits. It originated in the Middle East and has spread throughout Europe and beyond as a weed of cultivated fields and roadsides. The fruits are eaten as a supplement to diets in some parts of South Asia but are narcotic and potentially toxic in large quantities.
An archaeophyte is a plant species which is non-native to a geographical region, but which was an introduced species in "ancient" times, rather than being a modern introduction. Those arriving after are called neophytes.
Paterson's curse or Salvation Jane is an invasive plant species in Australia. There are a number of theories regarding where the name Salvation Jane originated, and it is mostly used in South Australia. These explanations include "salvation jane" referring to the flower which looks similar to the bonnets of Salvation Army ladies, its “salvation” to beekeepers because it is often in flower when the honeyflow is down, and due to its use as a source of emergency food for grazing animals when the less drought-tolerant grazing pastures die off. Other names are blueweed, Lady Campbell weed, Riverina bluebell, and purple viper's bugloss.
Lantana camara is a species of flowering plant within the verbena family (Verbenaceae), native to the American tropics. It is a very adaptable species, which can inhabit a wide variety of ecosystems; once it has been introduced into a habitat it spreads rapidly; between 45ºN and 45ºS and more than 1,400 metres in altitude.
Andropogon virginicus is a species of grass known by several common names, including broomsedge bluestem, yellowsedge bluestem and whiskey grass. It is native to the southeastern United States and as far north as the Great Lakes. It is known as an introduced species in California and Hawaii, where it is weedy.
Antigonon leptopus is a species of perennial vine in the buckwheat family commonly known as coral vine or queen's wreath. This clambering vine is characterized by showy, usually pink flowers that can bloom throughout the year and large, heart-shaped leaves. A. leptopus is native to the Pacific and Atlantic coastal plains of Mexico, but also occurs as a roadside weed from Mexico south to Central America. It is widely introduced and invasive throughout tropical regions of the world, including in the south and eastern United States, the West Indies, South America, and the Old World tropics of Asia and Africa. This species is utilized for its edible tubers and seeds, but also for its horticultural properties as an ornamental vine in warmer parts of the world.
In botany, a neophyte is a plant species which is not native to a geographical region and was introduced in recent history. Non-native plants that are long-established in an area are called archaeophytes. In Britain, neophytes are defined more specifically as plant species that were introduced after 1492, when Christopher Columbus arrived in the New World and the Columbian Exchange began.
Centaurea macrocephala is a species of flowering plant in the family Asteraceae, and a member of the thistle tribe, Cardueae (Cynareae). It has many common names, including bighead knapweed, big yellow centaurea, lemon fluff, yellow bachelor's button, yellow hardhat, and Armenian basketflower.
Garden waste, or green waste dumping is the act of discarding or depositing garden waste somewhere it does not belong.
Hemerochory, or anthropochory, is the distribution of cultivated plants or their seeds and cuttings, consciously or unconsciously, by humans into an area that they could not colonize through their natural mechanisms of spread, but are able to maintain themselves without specific human help in their new habitat.
Adventive plants or adventitious plants are plants that have established themselves in a place that does not correspond to their area of origin due to anthropogenic influence and, therefore, are all wild species that have only been established with the help of humans, in contrast to the native species.