Ragweeds are flowering plants in the genus ''Ambrosia'' in the aster

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae ...

. They are distributed in the

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

and

subtropical The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north a ...

regions of the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North America, North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. ...

, especially

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

,''Ambrosia''
Flora of North America. where the origin and

center of diversity A center of origin is a geographical area where a group of organisms, either domesticated or wild, first developed its distinctive properties. They are also considered centers of diversity. Centers of origin were first identified in 1924 by Ni ...

of the genus are in the

southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, N ...

and northwestern

Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...

. Several species have been introduced to the

Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by thei ...

and some have

naturalized Naturalization (or naturalisation) is the legal act or process by which a non-citizen of a country may acquire citizenship or nationality of that country. It may be done automatically by a statute, i.e., without any effort on the part of the in ...

and have become

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...

. Ragweed species are expected to continue spreading across Europe in the near future in response to ongoing climate change. Other common names include bursages''Ambrosia''
Integrated Taxonomic Information System (ITIS). and burrobrushes.''Ambrosia''
The Jepson eFlora 2013. The genus name is from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

ambrosia In the ancient Greek myths, ''ambrosia'' (, grc, ἀμβροσία 'immortality'), the food or drink of the Greek gods, is often depicted as conferring longevity or immortality upon whoever consumed it. It was brought to the gods in Olympus ...

'', meaning "food or drink of immortality". Ragweed

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametop ...

is notorious for causing

allergic reactions Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derm ...

in humans, specifically

allergic rhinitis Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, ...

. Up to half of all cases of pollen-related allergic rhinitis in North America are caused by ragweeds. The most widespread species of the genus in North America is ''

Ambrosia artemisiifolia ''Ambrosia artemisiifolia'', with the common names common ragweed, annual ragweed, and low ragweed, is a species of the genus ''Ambrosia'' native to regions of the Americas. Taxonomy The species name, ''artemisiifolia'', is given because the lea ...

''.

Description and ecology

Ragweeds are

annual Annual may refer to: *Annual publication, periodical publications appearing regularly once per year ** Yearbook ** Literary annual *Annual plant *Annual report *Annual giving *Annual, Morocco, a settlement in northeastern Morocco *Annuals (band), ...

and

perennial herbs A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also widel ...

and

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from tree ...

s. Species may grow just a few centimeters tall or exceed four meters in height. The stems are erect, decumbent or prostrate, and many grow from

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow ...

s. The leaves may be arranged alternately, oppositely, or both. The leaf blades come in many shapes, sometimes divided pinnately or palmately into lobes. The edges are smooth or toothed. Some are hairy, and most are glandular. Ragweeds are

monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is ...

, most producing

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are forme ...

s that contain both staminate and pistillate flowers. Inflorescences are often in the form of a spike or

raceme A raceme ( or ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the s ...

made up mostly of staminate flowers with some pistillate clusters around the base. Staminate flower heads have

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the fila ...

s surrounded by whitish or purplish florets. Pistillate flower heads have fruit-yielding ovules surrounded by many

phyllaries In botanical terminology, a phyllary, also known an involucral bract or tegule, is a single bract of the involucre of a composite flower. The involucre is the grouping of bracts together. Phyllaries are reduced leaf-like structures that form one o ...

and fewer, smaller florets. The pistillate flowers are

wind pollinated Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including grasses, sedges, and rushes. Other common anemophilous plan ...

,Genus ''Ambrosia''
Arizona-Sonora Desert Museum. and the fruits develop. They are burs, sometimes adorned with knobs, wings, or spines. Many ''Ambrosia'' species occur in

desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...

and semi-desert areas, and many are

ruderal species A ruderal species is a plant species that is first to colonize disturbed lands. The disturbance may be natural for example, wildfires or avalanchesor the consequences of human activities, such as construction ( of roads, of buildings, mining, et ...

that grow in disturbed habitat types.

Allergy

Ragweed pollen is a common

allergen An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies. In technical t ...

. A single plant may produce about a billion grains of pollen per season,Rees, A. M. ''Consumer Health USA: Essential Information from the Federal Health Network'' 2nd ed. Volume 2. Westwood, Connecticut: Greenwood, 1997. pg. 32. "Each ragweed plant produces about one billion pollen grains during an average allergy season". and the pollen is transported on the wind. It causes about half of all cases of pollen-associated allergic rhinitis in North America, where ragweeds are most abundant and diverse. Common culprits are common ragweed (''A. artemisiifolia'') and great ragweed (''A. trifida''). Concentration of ragweed pollen—in the absence of significant rainfall, which removes pollen from the air, is the lowest in the early morning hours (6:00 AM), when emissions starts. Pollen concentration peaks at midday. Ragweed pollen can remain airborne for days and travel great distances, and can even be carried out to sea. Ragweeds native to the Americas have been introduced to Europe starting in the nineteenth century and especially during

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

, and have spread rapidly since the 1950s. Eastern Europe, particularly

Hungary Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Cr ...

, has been badly affected by ragweed since the early 1990s, when the dismantling of Communist collective agriculture led to large-scale abandonment of agricultural land, and new building projects also resulted in disturbed, un-landscaped areas. The major allergenic compound in the pollen has been identified as ''Amb a 1'', a 38 k Da nonglycosylated protein composed of two

subunit Subunit may refer to: * Subunit HIV vaccine, a class of HIV vaccine *Protein subunit, a protein molecule that assembles with other protein molecules *Monomer, a molecule that may bind chemically to other molecules to form a polymer * Sub-subunit, ...

s. It also contains other allergenic components, such as

profilin Profilin is an actin-binding protein involved in the dynamic turnover and reconstruction of the actin cytoskeleton. It is found in all eukaryotic organisms. Profilin is important for spatially and temporally controlled growth of actin microfilame ...

and

calcium-binding protein Calcium-binding proteins are proteins that participate in calcium cell signalling pathways by binding to Ca2+, the calcium ion that plays an important role in many cellular processes. Calcium-binding proteins have specific domains that bind to cal ...

s. Ragweed allergy sufferers may show signs of

oral allergy syndrome Oral allergy syndrome (OAS) or pollen-food allergy is a type of food allergy classified by a cluster of allergic reactions in the mouth and throat in response to eating certain (usually fresh) fruits, nuts, and vegetables that typically develops ...

, a food allergy classified by a cluster of allergic reactions in the mouth in response to the consumption certain fruits, vegetables, and nuts. Foods commonly involved include

bean A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes th ...

celery Celery (''Apium graveolens'') is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, ...

cumin Cumin ( or , or Article title
) (''Cuminum cyminum'') is a

hazelnut The hazelnut is the fruit of the hazel tree and therefore includes any of the nuts deriving from species of the genus '' Corylus'', especially the nuts of the species ''Corylus avellana''. They are also known as cobnuts or filberts according ...

kiwifruit Kiwifruit (often shortened to kiwi in North American, British and continental European English) or Chinese gooseberry is the edible berry of several species of woody vines in the genus ''Actinidia''. The most common cultivar group of kiwif ...

parsley Parsley, or garden parsley (''Petroselinum crispum'') is a species of flowering plant in the family Apiaceae that is native to the central and eastern Mediterranean region (Sardinia, Lebanon, Israel, Cyprus, Turkey, southern Italy, Greece, ...

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Uni ...

es,

banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", disting ...

melon A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". T ...

cucumber Cucumber (''Cucumis sativus'') is a widely-cultivated creeping vine plant in the Cucurbitaceae family that bears usually cylindrical fruits, which are used as culinary vegetables.zucchini The zucchini (; plural: zucchini or zucchinis), courgette (; plural: courgettes) or baby marrow (''Cucurbita pepo'') is a summer squash, a vining herbaceous plant whose fruit are harvested when their immature seeds and epicarp (rind) are st ...

. Because cooking usually denatures the proteins that cause the reaction, the foods are more allergenic when eaten raw; exceptions are celery and nuts, which may not be safe even when cooked. Signs of reaction can include itching, burning, and swelling of the mouth and throat, runny eyes and nose,

hives Hives, also known as urticaria, is a kind of skin rash with red, raised, itchy bumps. Hives may burn or sting. The patches of rash may appear on different body parts, with variable duration from minutes to days, and does not leave any long-last ...

, and, less commonly, vomiting, diarrhea,

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...

, and

anaphylaxis Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the follo ...

. These symptoms are due to the abnormal increase of IgE antibodies which attach to a type of immune cell called mast cells. When the ragweed antigen then attaches to these antibodies the mast cells release histamine and other symptom evoking chemicals.

Merck & Co Merck & Co., Inc. is an American multinational pharmaceutical company headquartered in Rahway, New Jersey, and is named for Merck Group, founded in Germany in 1668, of whom it was once the American arm. The company does business as Merck Sharp ...

, under license from allergy immunotherapy (AIT) company ALK, has launched a ragweed allergy immunotherapy treatment in sublingual tablet form in the US and Canada. As of 2006, research into allergy immunotherapy treatment involved administering doses of the allergen to accustom the body to induce specific long-term tolerance.

Control and eradication

Chemical spraying has been used for control in large areas. Because ragweed only reacts to some of the more aggressive herbicides, it is highly recommended to consult professionals when deciding on dosage and methodology, especially near urban areas. Effective active ingredients include those that are

glyphosate Glyphosate (IUPAC name: ''N''-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plant enzyme 5-enolpyruvylshik ...

-based ( Roundup, Glyphogan, Glialka), sulfosate-based ( Medallon), and glufosinate ammonium-based ( Finale 14SL). In badly infested areas, are usually dispersed. In 2007 several ''Ambrosia artemisiifolia'' populations were glyphosate resistant, exclusively in the USA. Where herbicides cannot be used, mowing may be repeated about every three weeks, as it grows back rapidly. In the past, ragweed was usually cut down, left to dry, and then burned. This method is used less often now, because of the

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, th ...

caused by smoke. Manually uprooting ragweed is generally ineffective, and skin contact can cause allergic reaction. If uprooting is the method of choice, it should be performed before flowering. There is evidence that mechanical and chemical control methods are actually no more effective in the long run than leaving the weed in place. Fungal rusts and the leaf-eating beetle '' Ophraella communa'' have been proposed as agents of

biological pest control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also i ...

of ragweeds, but the latter may also attack

sunflower The common sunflower (''Helianthus annuus'') is a large annual forb of the genus ''Helianthus'' grown as a crop for its edible oily seeds. Apart from cooking oil production, it is also used as livestock forage (as a meal or a silage plant), ...

s, and applications for permits and funding to test these controls have been unsuccessful. The beetle has, however, appeared in Europe, either on its own or as an uncontrolled introduction, and it has started making a dent into Ambrosia populations there.

Species

There are about 50 species in genus ''Ambrosia''. Species include:''Ambrosia''
The Plant List. * ''

Ambrosia acanthicarpa ''Ambrosia acanthicarpa'' is a North American species of bristly annual plants in the family Asteraceae. Members of the genus ''Ambrosia (plant), Ambrosia'' are called ragweeds. The species has common names including flatspine bur ragweed, Hooker ...

'' Hook. – flatspine bur ragweed, annual bursage, sand bursage * '' Ambrosia acuminata'' (Brandegee) W.W.Payne * '' Ambrosia ambrosioides'' (Cav.) W.W.Payne – ambrosia-leaf bur ragweed, big bursage, ambrosia bursage * '' Ambrosia arborescens'' Mill. – marko, altamisa * ''

'' L. – common ragweed, short ragweed, Roman wormwood * '' Ambrosia artemisioides'' Meyen & Walp. * '' Ambrosia bidentata'' Michx. – lanceleaf ragweed, southern ragweed * '' Ambrosia bryantii'' (Curran) Payne * '' Ambrosia camphorata'' (Greene) W.W.Payne * '' Ambrosia canescens'' A.Gray – hairy ragweed * '' Ambrosia carduacea'' (Greene) W.W.Payne * '' Ambrosia chamissonis'' (Less.) Greene – silver burr ragweed, beach-bur * '' Ambrosia cheiranthifolia'' A.Gray – Rio Grande ragweed, South Texas ambrosia * '' Ambrosia chenopodiifolia'' (Benth.) W.W.Payne – San Diego bur ragweed, San Diego bursage * '' Ambrosia confertiflora'' DC. – weakleaf bur ragweed * '' Ambrosia cordifolia'' (A.Gray) W.W.Payne – Tucson bur ragweed, heartleaf bursage * '' Ambrosia deltoidea'' (Torr.) W.W.Payne – triangle bur ragweed, triangle bursage * '' Ambrosia dentata'' (Cabrera) M.O.Dillon * '' Ambrosia divaricata'' (Brandegee) Payne * '' Ambrosia diversifolia'' (Piper) Rydb. * ''

Ambrosia dumosa ''Ambrosia dumosa'', the burro-weed or white bursage, a North American species of plants in the family Asteraceae. It is a common constituent of the creosote-bush scrub community throughout the Mojave desert of California, Nevada, and Utah and ...

'' (A.Gray) W.W.Payne – burrobush, white bursage * '' Ambrosia eriocentra'' (A.Gray) W.W.Payne – woolly fruit bur ragweed, hollyleaf bursage * '' Ambrosia flexuosa'' (A.Gray) W.W.Payne * '' Ambrosia grayi'' (A.Nelson) Shinners – woollyleaf bur ragweed, lagoonweed * ''Ambrosia'' × ''helenae'' Rouleau – Helen ragweed * '' Ambrosia hispida'' Pursh – coastal ragweed * '' Ambrosia humi'' León de la Luz & Rebman * '' Ambrosia ilicifolia'' (A.Gray) W.W.Payne – hollyleaf bur ragweed * ''Ambrosia'' × ''intergradiens'' W.H.Wagner – intergrading ragweed * '' Ambrosia johnstoniorum'' Henrickson * '' Ambrosia linearis'' (Rydb.) W.W.Payne – streaked bur ragweed * '' Ambrosia magdalenae'' (Brandegee) W.W.Payne * '' Ambrosia maritima'' L. * '' Ambrosia microcephala'' DC. * '' Ambrosia monogyra'' (Torr. & A.Gray) Strother & B.G.Baldwin – singlewhorl burrobrush * '' Ambrosia nivea'' (B.L.Rob. & Fernald) W.W.Payne * '' Ambrosia pannosa'' W.W.Payne * '' Ambrosia peruviana'' Willd. – ragweed, altamisa * ''Ambrosia'' × ''platyspina'' (Seaman) Strother & B.G.Baldwin * '' Ambrosia polystachya'' DC. * ''

Ambrosia psilostachya ''Ambrosia psilostachya'' is a species of ragweed known by the common names Cuman ragweed and perennial ragweed, and western ragweed. Distribution and habitat The plant is widespread across much of North America (United States, Canada, and nort ...

'' DC. – Cuman ragweed, western ragweed, perennial ragweed * ''

Ambrosia pumila ''Ambrosia pumila'' is a rare species of herbaceous perennial plant known by the common names San Diego ragweed and San Diego ambrosia. It is native to far southern California, Baja California, and Baja California Sur. It grows in floodplains and ...

'' (Nutt.) A.Gray – dwarf bur ragweed, San Diego ambrosia * ''

Ambrosia salsola ''Ambrosia salsola'', commonly called cheesebush, winged ragweed, burrobush, white burrobrush, and desert pearl, is a species of perennial shrub in the family Asteraceae native to deserts of the southwestern United States and northwestern Mexico. ...

'' (Torr. & A. Gray) Strother & B.G. Baldwin * '' Ambrosia scabra'' Hook. & Arn. * '' Ambrosia tacorensis'' Meyen * '' Ambrosia tarapacana'' Phil. * ''

Ambrosia tenuifolia In the ancient Greek myths, ''ambrosia'' (, grc, ἀμβροσία 'immortality'), the food or drink of the Greek gods, is often depicted as conferring longevity or immortality upon whoever consumed it. It was brought to the gods in Olympus b ...

'' Spreng. – slimleaf bur ragweed, lacy ambrosia * '' Ambrosia tomentosa'' Nutt. – skeletonleaf bur ragweed * ''

Ambrosia trifida ''Ambrosia trifida'', the giant ragweed, is a species of flowering plant in the family Asteraceae. It is native to North America, where it is widespread in Canada, the United States, and northern Mexico. Distribution It is present in Europe a ...

'' L. – great ragweed, giant ragweed * '' Ambrosia velutina'' O.E.Schulz * '' Ambrosia villosissima'' Forssk.

References

External links