Yellow starthistle, a thistle native to southern Europe and the Middle East that is an invasive weed in parts of North America. Yellow Starthistle ( Centaurea Solstitialis) is a member of the Asteraceae family native to the Mediterranean region This article is about the plant for other uses see Thistle (disambiguation.

700 cattle that were killed overnight by a poisonous weed

A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-made settings such as gardens, lawns or agricultural areas, but also in parks, woods and other natural areas. Plants are living Organisms belonging to the kingdom Plantae. A garden is a planned space usually outdoors set aside for the display cultivation and enjoyment of Plants and other forms of Nature. A lawn is an area of recreational or amenity land planted with grass, and sometimes Clover and other plants which are maintained at a low even height Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture More specifically, the term is often used to describe native or nonnative plants that grow and reproduce aggressively. In Ecology, an indigenous Species is an Organism which is native to a given region or Ecosystem. ^[1]

Weeds may be unwanted because they are unsightly, or they limit the growth of other plants by blocking light or using up nutrients from the soil. A nutrient is food or chemicals that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment Soil, often typeset as SOiL, is a four piece rock band from Chicago Illinois United States founded by Shaun Glass Tom Schofield Tim King and Adam Zadel They also can harbor and spread plant pathogens that can infect and degrade the quality of crop or horticultural plants. A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious Horticulture is the art and science of plant cultivation Horticulturists (or horticuluralists) work and conduct research in the fields of Plant propagation Weeds may be a nuisance because they have thorns or prickles, cause skin irritation when contacted, or parts of the plants might come off and attach to fur or clothes.

Definition

The term weed in its general sense is a subjective one, without any classification value, since a "weed" is not a weed when growing where it belongs or is wanted. Indeed, a number of "weeds" have been used in gardens or other cultivated-plant settings. An example is the corncockle, Agrostemma, which was a common field weed exported from Europe along with wheat, but now sometimes grown as a garden plant. Agrostemma is a genus in the Caryophyllaceae family contiang the Species known as corncockles. Wheat ( Triticum spp is a worldwide cultivated grass from the Levant area of the Middle East. ^[2]

Distribution

Weedy plants generally share similar adaptations that give them advantages and allow them to proliferate in disturbed environments whose soil or natural vegetative cover has been damaged. An adaptation is a characteristic of an Organism that has been favored by Natural selection and Naturally occurring disturbed environments include dunes and other windswept areas with shifting soils, alluvial flood plains, river banks and deltas, and areas that are often burned. In physical Geography, a dune is a Hill of Sand built by Aeolian processes. Alluvium (from the Latin, alluvius, from alluere, "to wash against" is Soil or Sediments deposited by a river or other running A delta is a Landform where the mouth of a River flows into an Ocean, Sea, Estuary, Lake or another river Since human agricultural practices often mimic these natural environments where weedy species have evolved, weeds have adapted to grow and proliferate in human-disturbed areas such as agricultural fields, lawns, roadsides, and construction sites.

The weedy nature of these species often gives them an advantage over more desirable crop species because they often grow quickly and reproduce quickly, have seeds that persist in the soil seed bank for many years, or have short lifespans with multiple generations in the same growing season. Reproduction is the Biological process by which new individual Organisms are produced The soil seed bank is the collective name for the store of Seeds often dormant which are stored within the Soil of many terrestrial Ecosystems Perennial weeds often have underground stems that spread out under the soil surface or, like ground ivy (Glechoma hederacea), have creeping stems that root and spread out over the ground. Glechoma hederacea ( Ground-ivy; syn Nepeta glechoma Benth, Nepeta hederacea ( L ^[3] A number of weedy species have developed allelopathy, chemical means to prevent the germination or growth of neighboring plants. Allelopathy is the inhibition of growth of a plant due to Biomolecules released by another Germination is the process whereby growth emerges from a period of dormancy

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Relation to humans

As long as humans have cultivated plants, weeds have been a problem. Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture In Agriculture, agribusiness is a generic term that refers to the various Businesses involved in Food production including Farming, Seed Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture Agricultural science is a broad multidisciplinary field that encompasses the parts of exact natural economic and Social sciences that are used in the practice and understanding Agronomy is the science and technology of using plants for food fuel feed and fiber Animal husbandry, also called Animal science, stockbreeding or simple husbandry, is the agricultural practice of breeding Extensive farming (as opposed to Intensive farming) is an agricultural production system that uses little inputs on vast areas of land such as the Great Plains. Factory farming is the practice of raising Farm animals in confinement at high stocking density where a farm operates as a Factory &mdash a practice typical in Free range is a method of Farming Husbandry where the Animals are allowed to roam freely instead of being contained in any manner Industrial agriculture is a form of modern farming that refers to the industrialized production of Livestock, Poultry, Fish, and Intensive farming or intensive agriculture is an Agricultural production system characterized by the high Inputs of Capital, Fertilizers Organic farming is a form of agriculture that relies on Crop rotation, Green manure, Compost, Biological pest control, and mechanical Cultivation The word permaculture, coined by Australians Bill Mollison and David Holmgren during the 1970s is a Portmanteau of perma nent agri' Sustainable agriculture integrates three main goals environmental Stewardship, Farm Profitability and prosperous Farming communities Urban Agriculture and Peri-Urban Agriculture is the practice of cultivating processing and distributing food in or around (peri-urban a village town or city Agriculture was developed at least 10000 years ago and it has undergone significant developments since the time of the earliest cultivation The Neolithic Revolution was the first Agricultural revolution &mdashthe transition from hunting and gathering communities and bands to Agriculture and The Islamic Golden Age from the 8th century to the 13th century witnessed a fundamental transformation in Agriculture known as the Arab Agricultural The British Agricultural Revolution describes a period of development in Britain between the 18th century and the end of the 19th century which saw a massive increase in agricultural The Green Revolution refers to the transformation of Agriculture that began in 1945 at the request of the Mexican government to establish an agricultural research station to Aquaculture is the farming of freshwater and saltwater organisms including Molluscs Crustaceans and aquatic plants Christmas tree cultivation is an agricultural, Forestry, and horticultural occupation which involves growing Pine, Spruce, and Dairy farming is a class of agricultural, or an Animal husbandry enterprise for long-term production of Milk, which may be either processed on-site or Grazing generally describes a type of Predation in which an Herbivore feeds on Plants (such as Grasses, or more broadly on a multicellular Hydroponics (from the Greek words hydro (water and ponos (labour is a method of growing Plants using mineral Nutrient solutions without Integrated Multi-Trophic Aquaculture (IMTA is a practice in which the by-products (wastes from one species are recycled to become inputs ( Fertilizers Food) for another Intensive piggeries (or hog lots) are a type of Factory farm specialized for the raising of Domestic pigs up to slaughter weight Lumber or timber is Wood in any of its stages from felling through readiness for use as structural Material for Construction, or Maize (ˈmeɪz ( Zea mays L. ssp mays) known as corn in some countries is a cereal grain domesticated in Mesoamerica An orchard is an intentional planting of Trees or Shrubs maintained for Food production. Poultry farming is the practice of raising Poultry, such as Chickens turkeys ducks geese, as a subcategory of Animal husbandry A ranch is an area of landscape including various structures given primarily to the practice of ranching the practice of raising grazing livestock such as Cattle Rice is a Cereal foodstuff which forms an important part of the diet of many people worldwide and as such it is a staple food for many Sheep husbandry is the raising and breeding of Domestic sheep, and a subcategory of Animal husbandry. The System of Rice Intensification ( SRI) is a method of increasing the yield of Rice produced in Farming. Wheat ( Triticum spp is a worldwide cultivated grass from the Levant area of the Middle East. Weeds have even been mentioned in religious and literature texts like the following quotes from Genesis and a Shakespearean sonnet:

"Cursed is the ground because of you; through painful toil you will eat of it all the days of your life. William Shakespeare ( baptised The sonnet is one of the poetic forms that can be found in Lyric poetry from Europe. It will produce thorns and thistles for you, and you will eat the plants of the field. By the sweat of your brow you will eat your food until you return to the ground,"^[4]

"To thy fair flower add the rank smell of weeds: But why thy odour matcheth not thy show, The soil is this, that thou dost common grow. "^[5]

Weed seeds are often collected and transported with crops after the harvesting of grains, and so many weed species have moved out of their natural geographic locations and have spread around the world with humans. (See Invasive species. Introduced species|Weed Invasive species is a phrase with several definitions ) Not all weeds have the same ability to damage crops and horticultural plants. Some have been classified as noxious weeds because if left unchecked, they often dominate the environment where crop plants are to be grown. Noxious weeds are Plant species that have been designated by state or national agricultural authorities as plants that are injurious to agricultural and/or horticultural crops They are often foreign species mistakenly or accidentally imported into a region where there are few natural controls to limit their spread and population. Many weeds have ideal areas for growth and reproduction thanks to large areas of open soil created by the conversion of land to agriculture, and human distribution of food crops mixed with seeds of weeds from other parts of the world. Thus humans are the vector of transport and the producer of disturbed environments, so weedy species have an ideal association with humans.

A number of weeds, such as the dandelion Taraxacum, are edible, and their leaves and roots may be used for food or herbal medicine. Food is any substance usually composed primarily of Carbohydrates Fats water and/or Proteins that can be eaten or drunk by an Herbalism is a traditional Medicinal or Folk medicine practice based on the use of Plants and Plant extracts Herbalism is also known as Burdock is common weed over much of the world, and is sometimes used to make soup and other medicine in East Asia. Burdock is any of a group of biennial Thistles in the Genus Arctium, family Asteraceae Soup is a Food that is made by combining ingredients such as Meat and Vegetables in stock or hot/boiling Water, until the flavor These so-called "beneficial weeds" may have other beneficial effects, such as drawing away the attacks of crop-destroying insects, but often are breeding grounds for insects and pathogens that attack other plants. A Beneficial weed is any of various Plants not generally considered domesticated, but which nonetheless has some Companion plant effect or else is edible Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described Dandelions are one of several species which break up hardpan in overly cultivated fields, helping crops grow deeper root systems. In Soil science, Agriculture and Gardening, hardpan is a general term for a dense layer of Soil, residing usually below the uppermost Some modern species of domesticated flower actually originated as weeds in cultivated fields and have been bred by people into garden plants for their flowers or foliage. A flower, also known as a bloom or Blossom, is the reproductive structure found in Flowering plants (plants of the division Magnoliophyta, also

Examples

• Bindweed
• Broadleaf plantain - perennial, spreads by seeds that persist in the soil for many years
• Burdock - biennial
• Creeping Charlie - perennial, fast-spreading plants with long creeping stems
• Dandelion - perennial, wind-spread, fast-growing, and drought-tolerant
• Goldenrod - perennial
• Kudzu - perennial
• Leafy spurge - perennial, with underground stems
• Milk thistle - annual or biennial
• Poison ivy - perennial
• Ragweed - annual
• Sorrel - annual
• Sumac - woody perennial
• Wild carrot - biennial
• Wood sorrel - perennial

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See also

• Herbicide
• Introduced species
• Invasive species
• List of beneficial weeds
• Pesticide
• R-selection
• Vavilovian mimicry
• Weed control
• Weedy species

References

External links

• Weed Identification Guide from Virginia Tech (Southeastern United States)
• Common weeds of the northern United States and Canada from Canadian Weed Science Society