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Compositae or Asteraceae

The composite (also known as the daisy or sunflower family), as Compositae or Asteraceae are known, is one of the largest plant families. Almost 20,000 species are contained within this family. Most of these species are herbs but there are also some shrubs, trees and vines. The family includes many edible sala plants (e.g., lettuce, endive, chicory and artichoke), cultivated species such as the marigolds, daisies, sunflowers and chrysanthenums as well as many common weeds and wildflowers. It is primarily the latter, for example ragweed and mugwort , which are involved in pollen-induced seasonal allergies. [ 3 ]


Ragweed (Ambrosia)

Ambrosia sp.
Image source : [ 4 ]

Ragweed refers to the group of aproximately 15 species of weed plants, belonging to the Compositae family. Most ragweed species are native to North America, althought they are also found in Eastern Europe and the French Rhône valley [ 2 ] . The ragweeds are annuals characterised by their rough, hairy stems and mostly lobed or divided leaves. The ragweed flowers are greenish and inconspicuously concealed in small heads on the leaves.
The ragweed species, whose copious pollen is the main cause of seasonal allergic rhinitis (hayfever) in eastern and middle North America, are the common ragweed ( A. artemisiifolia ) and the great, or giant, ragweed ( A. trifida ). The common ragweed grows to about 1m (3.5 feet), is common all across North America and is also commonly refered to as Roman wormwood, hogweed, hogbrake or bitterweed. The giant ragweed, meanwhile, can reach anywhere up to 5 m (17 feet) in height and is native from Quebec to British Columbia in Canada and southward to Florida, Arkansas, and California in the USA. Due to the fact that ragweeds are annuals, they can be eradicated by being simply mowed before they release their pollen in late Summer. [ 1 , 3 ]

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Dandelion (Taraxacum)

A perennial weed of the genus Taraxacum and of the family Compositae . Althought the dandelion is a plant native to Eurasia, it is also common in temperate regions of North America. The most familiar species of dandelion is T. officinale , easily identifiable from its single, yellow flower and the fruit, which is a ball-shaped cluster of many small, white, tufted, one-seeded fruits for wind distribution. Although often considered a pest, the dandelion is also cultivated for food and medicine. The roots are often used as a coffee substitue and a laxative. One species is also cultivated to produce latex. [ 3 ]


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Goldenrod (Solidago)

The goldenrods are about 100 species of weedy, usually perennial herbs of the genus Solidago and Compositae family. Most species are native to North America and are characteristic of eastern North America where up to 60 species are found. Goldenrods are hardy and grow almost anywhere, from mountain-sides and woodlands to swamps. Both the Canadian goldenrod ( S. canadensis ) and the European Solidago virgaurea are cultivated as garden ornaments. [ 1 ]

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Mugwort (Artemisia vulgaris, A. campestris, A. dracunculus, A. rupestris, A. mutellina, A. absinthium, A. maritima, A. austriaca, A. pontica, A. laciniata, A. abrotanum, A. annua)

Artemisia tilessii
Image source : [ 4 ]

A shrubby weed most commonly found on waste land. Mugwort can reach heights of up to 2 meters (7 feet) and is characterised by quite small, yellow to reddish-brown flowers and a woody stem. The mugwort pollen season (in Central Europe) is generally late-July to September, with a peak around mid-August. Mugwort is known to cross react with almost all members of the Compositae family, especially the ragweeds , as well as dandelions , sunflowers, chamomilla and all daisy-like flowers. Mugwort also displays an important cross reaction in the context of food-allergies to celery. [ 2 ]

 

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Helianthus ( Helianthus tuberosus )

Helianthus annus
Image source : [ 5 ]

A member of the Compositae or sunflower family. Helianthus is the only root plant native to North America, which has gained economic importance. Its tubers are potato-like and a common foodstuff in both Europe and China. The tubers also contain inulin, which is an important source of fructose for diabetics. Alcohol can also be produced from Helianthus tubers. [ 3 ]




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[1] The Encyclopaedia Britannica Online : http://www.britannica.com
[2]
European Pollen Information : http://www.ngdc.noaa.gov/paleo/epd/
[3] The Concise Columbia Electronic Encyclopedia, Third Edition : http://www.encyclopaedia.com
[4]
Martin, Paul S., and Drew, Charles M., 1969. "Scanning electron photomicrographs of southwestern pollen grains."
    Journal Arizona Academy of Sciences 5 ( 3 ): 147 - 176. Palynology Department, University of Arizona : http://geo.arizona.edu/palynology
[5]
Martin, Paul S., and Drew, Charles M., 1970. "Additional scanning electron micrographs of southwestern pollen grains."
    Journal Arizona Academy of Sciences 6 ( 2 ): 140 - 161. Palynology Department, University of Arizona : http://geo.arizona.edu/palynology
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  http://www.hon.ch/Library/Theme/Allergy/Glossary/compositae.html Last modified: Wed Oct 20 2004