Ragweeds (Ambrosia Spp.)-The Hay Fever Weeds'

Home , Ambrosia artemisiifolia, Ambrosia trifida, Ragweed

Intriguing World of Weeds iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii Ragweeds (Ambrosia spp.)-The Hay Fever Weeds'

LARRY W. MITICH2

"Wither'd hogs ... on ragweed nags, They skim the muirs [moors]." Address to the Diel, 1785, Scottish poet Robert Burns (1759-1796).

INTRODUCTION Collectively, the ragweeds are one of the United States' few serious native weeds. They are members of the Aster aceae (Compositae), but for at least a century they were in their own famiiy, the Ambrosieae (a small family of about 55 native American taxa), having been separated from Compositae for convenience in 1828 by Ludwig [Heinrich Gottlieb] Reinchenbach ( 1793-1879), in his Conspectus regni vegtabilis (9). Ultimately, the ragweeds were placed in the Asteraceae (8, 18). The genus Ambrosia includes Franseria Cav. The Common ragweed new line up: 24 cosmopolitan species, 1 European (20). Treatise of Agriculture, where he remarked "The yellow Ambrosia means "food for the rag-weed, by which light land, when laid out to grass, is gods." Why it was used as a generic very much infested" (25). This invader from America had name for the ragweed is not known. already become troublesome in Great Britain. John Lin Blatchey (8) expounded that the person" ... who first used dley and Thomas Moore were the first to use the term in it may have had the equine god in mind, for horses are very the U.S. in their The Treasury ofBotany, published in 1866; fond of this species, often forsaking other food for its juicy they refer to "Ragweed ambrosia trifide [sic]" (25). leaves and branches. Among the poorer classes about the Linneaus described common ragweed, Ambrosia arte larger towns and cities quantities of it are gathered in misiifolia, and giant ragweed, A. trifida, in his Species August and September to be used instead of hay ... As one Plantarum in 1753 (9). Overthe years, 20 scientific names walks or drives along streams or thr~mgh low ground including species, subspecies, varieties, and forms have woodlands in early autumn he whiffs its peculiar odor been placed in synonymy under A. artemisiifolia, includ which is exhaled readily, bounteously, to all comers. To ing A. elatior L. and A. artemisiifolia L. var. elatior (L.) some persons it is doubtless disagreeable, but to me it is (23). rich, strong, powerful-fit odor for the gods." Augustin Pyramus de Candolle ( 1778-1841) named The word ragweed first entered the English language in perennial ragweed, A. psilostachya, in his Prodromus regni 1658 when Sir Thomas Browne wrote in The Gardens of vegetabilis, published in 1836 (9). In Greek psi/us= bare, Cyprus, ". . . it is often observable in furre, pillitory, smooth, uncovered, and stachys = an ear of grain, in Ragweed, [etc.]." This was followed in 1682 by Sir George reference to the plant's slender seed head (19). Synonymy Wheler's comment in A Journey into Greece, "The leaves under this taxon embraces 11 scientific names including are ... something like ragweed." In 1765 Adam Dickson species, subspecies, and varieties. However, the only fre was the first to refer to the weedy aspects of the plant in A quently used ones are A. coronopifolia T. & G. and A. psilostachya DC. var. coronopifolia (T. & G.) Farwell (23). 1No. 52 of the series "Intriguing World qf Weeds." 2Ext. Weed Sci. Emeritus, Dep. Vegetabl'e Crops, Univ. California, Davis, CA Common ragweed was recorded as early as 1838 in 95616. Michigan (27). In 1860 at Prescott, Ontario, one of the

236 Weed Technology. 1996. Volume 10:236-240 WEED TECHNOLOGY earliest collections of common ragweed in eastern Canada the most common of weeds, intruding almost everywhere; was made (6). it is a pest in meadows and pastures, for, though cattle do In Ontario, Ambrosia fossil pollen is present all through not relish its bitter juices, they will sometimes eat it when the postglacial time (6). Ambrosia pollen also has been better forage is scar-::e and, as a consequence, yield bitter found in Quebec in interglacial deposits older than 60,000 milk with a bad odor. After the removal of a grain crop this yr. In late-glacial time, unvegetated land resulting from plant nearly always springs up in the stubble." Once in the retreating glaciers apparently provided suitable habitats for soil, seeds survive for years, springing up when opportu the northern migration and spread of ragweeds. Only nity offers; they are a common impurity of grain and grass within the last 200 yr or so have ragweeds become abun seed and are also distributed in baled hay ( 17). dant again, an increase that coincides with settlement by In the mid-19th century, common ragweed was consid pioneers and tree removal for large farms (6). ered a"... worthless weed that occurs in most cultivated Perennial ragweed, native to western North America, grounds, and is usually very abundant among the stubble, has been in eastern Canada for a considerable time. Shortly after a crop of wheat: but, if the land be good, the plant after the retreat of the Wisconsin ice, perennial ragweed seems to be smothered or choked out, the next season, by migrated from the southwest into the eastern areas (6). the crop of clover and timothy. It is always ready, how Giant ragweed fruits from pre-Columbian Indian rock ever-like several other coarse weeds-to make its ap shelters have been found in Arkansas, Missouri, and Ken pearance whenever the grassy turf is broken up" ( 11 ). tucky (7). Perennial ragweed, an erect perennial, grows to 3 to 105 cm high, with horizontal running rootstocks; it spreads by seeds and rhizomes. The stems are unbranched or DESCRIPTIONS AND COMMENTS branched, and are pubescent with stiff, short, minutely Common ragweed is a very variable species, with plants glandular hairs. The leaves are mostly opposite below and differing in size, leaf shape, inflorescence form, and degree alternate above, and are thickish, light green to grayish of hairiness. Its specific epithet artemisiifolia is from the green, with margins that are entire or sparsely serrate. The Greek artemis, referring to Diana3, and the Latin folia, of flower heads contain either male or female flowers and are foloim, leaf; akin to many layers of leaves (29). borne on different parts of the same plant. The male heads An erect annual herb, it grows 5 to 70 cm high with a are 10 to 40 flowered, stalked to subsessile, and arranged tap root, and it spreads only by seeds. Its stems may be in spikes terminating the stems and branchlets. The female unbranched to bushy branched, and glabrous to rough heads are one-flowered, sessile, and single or clustered in hairy. The leaves are short-stalked, mostly opposite below, the upper axils (4). alternate above, thin, and pinnatifid to tri-pinnatifid. Rag While perennial ragweed is very similar in appearance weed flower heads contain either male or female flowers, to common ragweed, it is usually a smaller plant with the male heads being 10 to 100 flowered, and are borne in rougher and thicker stems, and less lobed leaves. It is spikes terminating the stems and branchlets (4). The slen common in dry soil; abandoned fields, vacant lots, road der racemes of little green staminate flowers, like knots or sides, and railway embankments are perennial ragweed's beads along the stem, produce a bounteous crop of yellow favorite haunts. It occurs from Illinois to the Northwest pollen which thickly coats the clothing of whoever passes Territory, southward to Texas, Mexico, and California ( 17), through a clump of ragweed on a summer day (8). The male and especially in the Rocky Mountain states (22). Peren and female flower heads usually occur on different parts nial ragweeed is a much harder weed to combat than its of the same plant; rarely are plants entirely female (4). annual relatives, for care in cultivation is necessary to For a long time, the weed was known as Roman worm avoid breaking up and spreading abroad the creeping root wood and hogweed. A troublesome weed that is very stocks and thus increasing the plague (17). generally distributed throughout the U.S. (22), its range Giant ragweed, an erect annual, grows from 30 to 300 also includes Canada, from Nova Scotia to British Colum (avg 150) cm high making it one of the largest annual bia (17). In 1914 Ada Georgia (17) commented: "One of weeds (8). It is fibrous-rooted with a relatively short tap root. The plants are rough hairy, and its leaves are opposite, palmately three-lobed, but occasionally five-lobed or even 3Diana was the virgin huntress and the goddess of forests and hills. As Zimdahl (29) explains, "Tying the name to Diana is remote from our experience." unlobed, with serrate margins. Its botanical name trifida is

Volume 10, Issue I (January-March) 1996 237

1/i, INTRIGUING WORLD OF WEEDS from the Latin tri, three, andfindere, to divide, referring to giant ragweed yields considerable amo1,1nts of high nutri its deeply three-lobed leaves (29). Flowers are produced in tive value forage (14), especially during its seedling stage. greenish heads, each head containing either only female or However, it eventually overtops and out competes numer male flowers. Giant ragweed flowers are wind-pollinated ous companion annual species (4). Wrote Georgia (17) in (1). 1914, "It is a huge, coarse plant, occupying so much room Giant ragweed produces bounteous seeds, and though and feeding so grossly that crops growing with it are the plants are easily destroyed, the seeds retain their vitality crowded and starved to death." and are readily carried from place to place by drifting snow (17, 22). The seeds (caryopses) are 6 to 8 mm long and consist of one central beak surrounded by a circle of five HAY FEVER AND DERMATITIS or more marginal points, giving a king's crown appearance, Common ragweed is the most important cause of hay hence the plant's common names-kinghead and crown fever in eastern North America (4). Both the plant and its weed; it also is known as horseweed (not the same as pollen may produce a dermatitis in some people who may Conyza). These spines, or tubercles, give much trouble in not suffer from hay fever (4). And ragweed oil dermatitis cleaning it from other seeds, as they catch in the screens; commonly affects male outdoor workers over 40 yr of age also they contain air spaces, which enable the fruits to float (15). The large amounts of airborne pollen shed by giant on water (17). In fact the seeds are scattered far and wide ragweed also is an important contributor to late summer by flood waters (8). hay fever (4). People contacting giant ragweed have a low Giant ragweed ranges from Nova Scotia westward to the sensitizing capacity to it (21). Perennial ragweed, too, Northwest Territory, Florida, Nebraska, Colorado, and Ar sheds large quantities of air-borne pollen that causes hay kansas ( 17). Prior to flowering, unlobed leafy forms of fever symptoms (28). However, it is of lesser importance giant ragweed may be mistaken for sunflowers (Helianthus than common ragweed as a cause of hay fever because of spp.), cockleburs (Xanthium spp.) or marshelder (Iva xan its more localized occurrence and its smaller size. thifolia Nutt.). However, marshelder stems are smooth and cocklebur's and sunflower's leaves are primarily alternate; giant ragweed stems are rough and hairy and the leaves are USES opposite (16). Common ragweed has several primal medical uses. The Giant ragweed plants produce new stems and inflores fluid extract from flowering plants is used to terminate cences when cut in late July and August during the com local bleeding (4). The bitter tonic made from the plant is bining of grain fields. Commented Darlington ( 11) in 1859, sometimes used for dyspepsia. In Virginia during the early "This coarse ugly weed is sufficiently common, and worth 1930s, common ragweed was second only to legumes as less, to entitle it to the notice of every farmer who desires winter food for quail. The oil content of common ragweed to keep his premises clear of such nuisances." is about the same as soybean (Glycine max Merr.), but it Early in the 20th century, Georgia ( 17) gave this advice has better drying properties; the oil was once suggested as for controlling giant ragweed: "If allowed to approach a use in paints or varnishes (24). Perennial ragweed seeds maturity it pays to hand-pull the weed, for the stout, woody probably are used as a winter food by many bird species stalks so dull and break the blades of mowers and reapers, (3). Indians prepared a tea from it. The plant inhibits cause so much waste of binding twine, and are so clogging growth of nitrogen-fixing bacteria, algae, and controls to the feed-way of threshing machines, that the earlier some grasses through allelopathy (20). In the Mediterrean handwork is really an economy." area A. maritima L. is used to flavor in liqueurs, and in Uruguay, A. tenuifolia Sprengel is used to control fertility (20). ECONOMIC IMPORTANCE Common ragweed, the most abundant of the ragweeds, DISTRIBUTION AND HABITAT infests grain and cultivated fields, open disturbed habitats, and roadsides. But precise values of losses resulting from A North American native, common ragweed is widely the presence of the weed are difficult if not impossible to introduced in Europe, Asia, and South America. Outside obtain (12). When grazed in large amounts by livestock, North America, perennial ragweed has been found in many

238 Volume 10, Issue I (January-March) 1996 WEED TECHNOLOGY countries of E•irope (4) and in Australia. Worldwide all plowing effects (26). However, agricultural techniques kill ragweed species occur most commonly between latitudes many seedlings. 45° and 30°, both north and south (2). Perennial ragweed survives and spreads primarily by Common ragweed is widespread on arable l~nd and spreading rootstocks. Where winters are extremely cold, grows in clay, silt, and sand mixtures in disturbed situ the roots survive and continue growing the following ations. Stem height ranges from a few cm on plants in light spring. New shoots arising from creeping rootstocks may sandy soils, to over 1 m on plants growing in heavy fertile require more than I yr to reach flowering; usually only a soils (4). Temperature is the most important factor affect few seeds develop at maturity on such shoots (27). ing its germination, which also increases greatly after Perennial ragweed produces one pistillate flower per grassland burning (10). In fields planted to clover (Trifo head, resulting in one seed, but since reproduction takes lium sp.) and alfalfa (Medicago sp.), widely dispersed place largely by vegetative means, seed production is of plants of common ragweed may occur the first year. The secondary importance (27). Despite the small seed set, an weed is very scarce or absent in permanent pastures, lawns, area can be readily colonized by one or a few original plants marshes, and woodlands. through its spreading roots tocks. In the first year from seed, Giant ragweed, also native to North America, is widely individual plants do not produce additional shoots from its distributed in Europe (5) and Japan. It thrives in wet root system. However, in the second year new shoots low-lying pastures, cultivated fields, orchards, roadside emerge from creeping rootstocks, thus establishing a clone ditches, river banks, and waste places, usually on rather (27). rich, disturbed, moist soils (17). Giant ragweed is essen Continuous cutting of perennial ragweed during the tially a floodplain species; it is rare in low rainfall areas summer months is necessary to prevent flowering and (5). When present in disturbed habitats, it is the dominant subsequent seed development. This must be done for sev species throughout the entire growing season. By being the eral years to eradicate the plant through starving the first to emerge in early spring, giant ragweed has an initial spreading rootstocks (4). competitive advantage over other summer annuals in sites plowed late in late fall or early spring (5)-. Perennial ragweed thrives in disturbed sites (4). In LITERATURE CITED Michigan it forms large clones by proliferation from un I. Abul-Fatih, H. A. 1977. Population biology of Ambrosia trifida, an annual community organizer. Univ. Microfilms Inc., Ann Arbor, Mich. 141 p. derground parts in disturbed habitats, especially around 2. Allard, H. A. 1943. The North American ragweeds and their occurrence in populated areas; the species also will invade grassy fields other parts of the world. Science 98:292-294. 3. Baldwin, W. P. and C. 0. Handley. 1946. Winter food of bobwhite quail in (27). Virginia. J. Wildl. Manage. 10: 142-149. 4. Bassett, I. J. and C. W. Crompton. 1975. The biology of Canadian weeds. 11. Ambrosia_ artemisiifolia L. and A. pilostachya DC. Can J. Plant Sci. 55:463-476. 5. Bassett, I. J. and C. W. Compton. 1982. The biology of Canadian weeds. 55. GROWTH AND DEVELOPMENT Ambrosia tri.fida L. Can. J. Plant Sci. 62: I 003-1010. 6. Bassett, I. J. and J. Terasmae. 1962. Ragweeds, Ambrosia species, in Canada Common ragweed is primarily wind-pollinated; if in and their history in postglacial time. Can. J. Plant Sci. 40:141-150. 7. Blake, S. F. 1939. A new variety of Iva ciliata from Indian rock shelters in sects visit the flowers it is only to consume the pollen (28). the southcentral United States. Rhodora 41:81-86. It produces one pistillate flower per head, resulting in one 8. Blatchley, W. S. 1930. The Indiana Weed Book. The Nature Publishing Co., Indianapolis. 191 p. seed; the number per small plant averages slightly more 9. Britton, N. L. and A. Brown. 1898. An Illustrated Flora of the Northern than 3,000 seeds while large plants produce up to 62,000 United States, Canada and the British Possessions. Vol. 3. Charles Scribner's seeds (13). Water, birds, and man are important in spread Sons, New York. 10. ·Curtis, J. T. and M. L. Partch. I 948. Effect offire on the competition between ing common ragweed (4). Wind plays a minor role in bluegrass and certain prairie plants. Am. Midi. Nat. 39:437-443. dispersal-no seeds were found beyond 2 m from experi 11. Darlington, W. 1859. American Weeds and Useful Plants. Orange Judd & Company, New York. 460 p. mental plants (12). 12. Dickerson, C. 1968. Studies on the germination, growth, development and Few predators kill growing common ragweed plants. control of common ragweed (Ambrosia artemisiifolia L.). Univ. Microfilms Inc., Ann Arbor, Mich. 162 p. Fungal "damping off' of postemergence seedlings prob 13. Dickerson, C. and R. D. Sweet. 1971. Common ragweed ecotypes. Weed ably is insignificant in field environments (4). It is able to Sci. 19:64-66. 14. Dustman, E. J. and L. C. Shiver. 1946. The chemical composition of adapt to mowing, trampling, and grazing. Because of seed Ambrosia trifida at successive growth stages. J. Am. Soc. Agron. 23:190- longevity, common ragweed survives cultivation and 194.

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15. Promer, J. L. and W. S. Burrage. 1953. Ragweed oil dermatitis. J. Allergy Compositae family. U. I. The genus Ambrosia-the ragweeds. Wisconsin 24:425-433. Acad. Sci. Arts and Letters 58:351-371. 16. Frankton, C. and G. A. Mulligan. 1970. Weeds of Canada. Queen's Printer, 24. Roedel, G. F. and M. H. Thornton. 1942. The composition and properties of Ottawa, Ont. 217 p. ragweed seed oil. J. Am. Oil Chem. Soc. 19:153-156. 17. Georgia, A. 1942. Manual of Weeds. The Macmillan Co., New York. 593 p. 25. Simpson, J. A. and E.S.C. Weiner. 1989. The Oxford English Dictionary, 18. Gledhill, D. 1989. The Names of Plants. 2nd ed. Cambridge University 2nd ed. Clarendon Press, Oxford. Press, Cambridge. 202 p. 26. Toole, E. H. and E. Brown. 1946. Final results of the Durvel buried seed 19. Jaeger,E. C. 1944. A Source-book ofBiological Names and Terms (2nd ed.). experiment. J. Agric. Res. 72:201-210. Charles C. Thomas, Springfield, IL. 257 p. 20. Mabberley, D. J. 1989. The Plant-Book. Cambridge University Press, Cam 27. Wagner, W. H. and T. F. Beals. 1958. Perennial ragweeds (Ambrosia) in bridge. 706 p. Michigan, with the description of a new, intermediate taxon. Rhodora 21. Mitchell, J. and A. Rook. 1979. Botanical Dermatology. Greengrass Publi 60: 177-204. cations, Vancouver. 787 p. 28. Wodehouse, R. P. 1971. Hayfever plants. 2nd ed. Hafner Publ. Co., New 22. Pammel, L. H. 1925. Weeds of the Farm and Garden. Orange Judd Publish York. 280p. ing Co., New York. 281 p. 29. Zimdahl, R. L. 1989. Weeds and Words. Iowa State University Press, Ames. 23. Payne, W. W. 1970. Preliminary reports on the flora of Wisconsin No. 62. 125 p.

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