'I: ~­ l < '.;· The Intriguing World of Weeds iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii Common Pokeweed 1

Larry W. Mitich2

INTRODUCTION Phytolaccaceae, virtually a tropical family, encom­ passes from 15 to 18 genera (11), usually herbs, but also a few tropical trees and shrubs (13). Of the 25 species in the genus Phytolacca (11), only one is represented in eastern North America (l). Unlike all the other New World species of Phytolacca, common pokeweed (P. americana L., soy. P. decandra L.) has its range centered north of the tropics ( 15). It is indige­ nous to almost the entire eastern half of the U.S. (8) and in Canada it occurs north to Quebec and Ontario (18); in Mexico it is confined to a small area in the extreme northeast (15). The generic name Phytolacca is derived from phyto, a In the U.S., common pokeweed is plant, and lacca, a Latinized form of lac, referring to the generally found from Maine to Minne­ crimson-colored juice of the berries. In spite of its apparent sota, then south to Florida and Texas. It simplicity, the commonest names of poke and pokeweed grows along roadsides, on hills, in are derived from the Virginia Indian pokon (from pak clearings, around barnyards, and in un­ which meant blood) and alludes to any red-juiced plant used as a stain or dye (4, 8). cultivated soils, especially in rich, moist loam. The first available historical records of pokeweed were made during colonial times in New England, Pennsylva­ DESCRIPTION AND COMMON NAMES nia, and Virginia. The plant seldom is found in areas where Common pokeweed, a strong-smelling hardy herba­ the temperature falls below minus 15 C in an average ceous perennial, has smooth, fleshy stems that die back to winter. However, its range can be correlated more closely the ground in winter. The plant attains a height of up to 3.5 with summer temperatures-it needs an average July tem­ m, and its dark green, alternate, lanceolate leaves are up to perature of over 20 C in order to thrive (15). 25 cm long. The flowers, borne in dense, simple racemes, are numerous, small, white or greenish, with sepals and no NOMENCLATURE AND ETYMOLOGY petals and appear in July and August. The fruit is a 10- There is a discrepancy in common pokeweed's specific seeded, inky-juiced, shiny, purple berry (8). name. Gray's Manual of Botany gives it as P. decandra L., The plant's shape has been likened to that of a small tree. while nearly all other authorities give it as P. americana However, its trunk-like stem is hollow. Since the root is L.; decandra means 10-stamened (17). perennial, the plant must remain undisturbed for several In 1905, J. K. Small described P. rigida from Florida years to attain its maximum size ( 17). (16). He considered it a species because it differs from Pokeweed is so different from any other weed that even common pokeweed in several characters. However, it is the most uninterested observers have a name for it ( 17). not sufficiently distinct to deserve recognition as a separate Common names include Virginia pokeweed, garget, skoke, species. Consequently Caulkins and Wyatt proposed a new bear's grape, American spinach, crowberry, cancer root, combination: P. americana var. rigida (2). and American nightshade (9). Pigeonberry is an old nick­ name dating to the days before the passenger pigeons were exterminated; the berries had been one of their favorite 1No. 47 of the series "Intriguing World of Weeds." 2Ext. Weed Sci., Dep. Vegetable Crops, Univ. California, Davis, CA 95616. foods (4). The purplish-crimson juice of the berries was

887 Weed Technology. 1994. Volume 8:887-890 ' t THE INTRIGUING WORLD OF WEEDS sometimes used as an ink, hence inkberry, yet another USE IN MEDICINE common name (4 ). The Delaware Indians probably were the first to use During James Knox Polk's presidential campaign in pokeweed in medicine, prescribing it as a form of cardiac 1845, pokeweed twigs were worn by his followers. Later, stimulant, and tribes in Virginia used it as a strong physic some people believed that the plant had gotten its name They also used a pokeweed poultice for cancers, scrofulu from the 11th President. But pokeweed had been called that the 'itch,' and rheumatism, and in small doses for syphilis long before President Polk (1795-1849) arrived on the (4). political scene (4). Early settlers soon adopted the Indian medical uses of pokeweed. Occasionally, human poisoning resulted from ,,1 ill-advised treatments or accidental ingestion of the plant COLONIZATION (5). But the popularity of the plant remained. Prior to 1900, pokeweed still had considerable pharmaceutical and folk The general range of pokeweed has been greatly ex­ medicine uses (12, 14). Kalm (7) recounts an incident tended by man in the last few centuries. Because of its involving a Mr. Bartram, who, having hit his foot against useful properties the plant was deliberately introduced into a stone, "had gotten a violent pain in it; that he then other countries. bethought himself of putting a leaf of the pokeweed on his Pokeweed's most conspicuously successful coloniza­ foot, by which he lost the pain in a short time." Darlingtc tion abroad is in Africa and the countries bordering the (3) states that the "tincture of the ripe berries is, or was,, Mediterranean Sea, where it was introduced about 1650. It popular remedy for chronic rheumatism." In 1914, the drug ranges northward into Switzerland, southern Germany, market price for the root was 4 to 11 cents a kg and the Austria, Hungary, and Russia, eastward to Iran, and west­ berries 5 cents a kg (6). ward to the Azores, the Canary Islands, and Cape Verdes. Common pokeweed is still being used in the preparation Its berries proved so useful for coloring low-grade wines of medicines ( 18). The pla11t contains more than one physi­ that the plant became widely cultivated in Portugal, Spain, ologically active principle, the most active one being phy­ France, and Italy. Escaping from cultivation, pokeweed has tolaccin, an alkaloid (9). Extracts of the root show saponic become a fairly common weed in this region. Occasionally, characteristics (8). pokeweed has been planted as an ornamental in some The plant's stout tap root, the principal medicinal part, European countries, including England, Germany, and was prescribed in small amounts, generally from 1 to 5 France (15). grains, for its emetic, cathartic, alterative, and slightly narcotic principles. During the 19th century, it was ern ployed to excite the "whole glandular system, and is very SEED DISPERSAL AND VITALITY useful in syphilitic, scrofulous, rheumatic and cutaneous Traveling in North America in mid-1700, Kalm (7) diseases." The fully ripe berries were similarly dispensed, observed that the robins "eat its dark crimson-juiced ber­ but are milder in action (9). Common pokeweed also has ries." Indeed, birds are the usual dispersers of pokeweed been tested experimentally in the treatment of certain kinds seed, as is suggested by the close association of pokeweed of cancer (9). with bushes and fences as well as by the sudden outbursts Farmers and dairymen use an extract or tincture of of isolated new colonies. In A Bunch of Herbs, published phytolacca for reducing caking and swelling of cows' in 1881, John Burroughs observed: "Pokeweed never in­ udders. They prepare a mixture of phytolacca and lanolin vades cultivated fields, but hovers about the borders and (wool oil) and rub this into the udders ( 17). 'looks' over the fences (4)." Birds eat pokeberries fre­ quently and regularly~ at times the berries form one of the RECENT MEDICAL ADVANCES chief foods of the small migratory birds ( 15). Pokeweed seeds remain viable for at least 40 years. An antiviral protein has been found in common poke­ Their long life allows the seeds to accumulate in the soil weed. Genetic engineers have cloned a protein from the from occasional bird droppings over a long period of years leaves of pokeweed that could be the most effective agent until some disruption provides conditions suitable for ger­ yet to inhibit HIV, the virus that causes AIDS. Pokeweed mination (15). antiviral protein (PAP), a plant protein of relative molecu-

888 Volume 8, Issue 4 (October-December) 1994 L WEED TECHNOLOGY lar mass 30,000, will inhibit HIV from replicating in hu­ the plant is not particularly palatable (8). While the ber­ man cells. Even in minute amounts, the protein may pre­ ries-the most attractive part of the plant-are the least vent cells from becoming infected with HIV, as well as toxic, they may have been responsible for human fatalities stopping the virus replicating once it has invaded cells ( 19, (12). However,_wild birds readily eat them without appar­ 20, 21). PAP also inhibits replication of certain plant RNA ent toxic effect, and feeding experiments have shown them viruses and the herpes simplex virus, among others ( 19). harmless to domestic fowl (8). Exogenous applications of PAP protects heterologous Pigs have been poisoned by consuming the roots. Ex­ plants from viral infections. Expression of PAP in trans­ perimental feeding of a few small pieces of the root to a genic plants offers the possibility of developing resistance pig resulted in nausea, depression, and prostration the next to a broad spectrum of plant viruses by expression of a day. The animal was killed in a moribund condition. single gene (10). The symptoms of pokeweed poisoning in humans in­ volve a burning sensation in the mouth immediately upon USE AS FOOD consumption, followed by gastrointestinal cramps, vomi­ tion, and diarrhea in about 2 hours. While recovery usually The Delaware and Virginia Indian tribes removed the occurs in 24 hours, some victims die (8). more succulent growths in spring and cooked them in the way spinach or asparagus is today, excluding any part of the poisonous root (4). This practice is widely regarded as EARLY CONTROL safe if the cooking water is discarded (8). These young Until contemporary times, landowners having a com­ shoots are still found on some American markets under the mon pokeweed infestation were advised to "grub out name of 'sprouts' (4). wholly, selling root and fruit to pay for the trouble if Famous author Marjorie Kinnan Rawlings wrote about possible; or cut off below the crown and apply dry salt, pokeweed in her 1942 best seller Cross Creek: 'I hunt ... carbolic acid or kerosene to the cut surface of the root" (6). for the most tender shoots, cutting those from 6 to 8 inches Since the weed is usually confined to waste areas, it is in length. I trim off the leaves and thin skin and cook the still generally controlled mechanically. shoots exactly as I do asparagus ... The flavor is delicate and delicious, with a faint taste of iron" (4). BIOLOGICAL CONTROL POTENTIAL In 1859, Darlington (3) wrote that "the mature berries have been used by the pastry cook in making pies of Pokeweed leaves are often mottled by a mosaic disease equivocal merit." ( 17), leading researchers to investigate the use of fungal pathogens as mycoherbicides against this weed. Phoma OTHER USES sorghina, isolated from leaf spots on pokeweed, is being evaluated for its potential as a biocontrol agent. However, In the mid 1790s, Kalm (7) wrote: "When the juice of more studies need to be done before conclusions can be its berries is put upon paper or the like, it dyes it a deep made (19). purple, which is as fine as any in the world, and it is a pity that no method has as yet been discovered of making this color last on woolen or linen cloth, for it fades very soon." LITERATURE CITED However, the juice was also employed as a food dye in I. Britton, N. L. and A. Brown. 1898. An Illustrated Flora of the Northern United States, Canada and the British Possessions. Volume I. Charles confectionery (4). Scribner's Sons, New York. American writer Henry David Thoreau (1817-1862) 2. Caulkins, D. B. and R. Wyatt. 1990. Variation and taxonomy of Phytolacca coveted its strong purple stalk for a cane (4). But despite americana and P. rigida in the southeastern United States. Bull. Torrey Bot. Club 117:357-367. all of its uses, Darlington, in 1859, commented, "Notwith­ 3. Darlington, W. 1859. American Weeds and Useful Plants. Orange Judd & standing all this, the plant is regarded and treated as a weed Co., New York. 460 p. 4. Durant, Mary. 1976. Who Named the Daisy? Who Named the Rose? Dodd, by all neat farmers" (3). Mead and Co., New York. 214 p. 5. French, C. 1900. Pokeroot Poisoning. New York Med. J. 72:653. 6. George, A. 1942. Manual of Weeds. The Macmillan Co., New York. 593 p. THE POISONOUS PRINCIPLE 7. Kalm, P. 1937. Travels into North America, 1749-1751. 2 vols. Wilson­ Erickson, Inc., New York. Poisoning in animals is rare, partly because the most 8. Kingsbury, J.M. 1964. Poisonous Plants of the United States and Canada. toxic part of the plant is underground, and partly because Prentice-Hall, Inc., Englewood Cliffs. NJ. 626 p.

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9. LeStrange, R. 1977. A History of Herbal Plants. Angus and Robertson, 16. Small, J. K. 1905. Additions to the flora of sub-tropical Florida. Bull. New Publishers, London. 304 p. York Bot. Gard. 3:419-440. 10. Lodge, J. K., W. K. Kaniewski, and N. E. Turner. 1993. Broad-spectrum 17. Spencer, E. R. 1968. All About Weeds. Dover Publications, Inc., New York. virus resistance in transgenic plants expressing pokeweed antiviral protein. 333 p. Proc. Nat. Acad. Sci. U.S.A. 90:7089-7093. 18. United States Department of Agriculture. 1970. Selected Weeds of th,· 11. Mabberley, D. J. 1989. The Plant-Book. Cambridge University Press, Cam­ United States. Agriculture Handbook No. 346. 463 p. bridge, England. 706 p. 19. Venkatasubbaiah, C. C., C. G. Van Dyke, and W. S. Chilton. 1992. Ph, 12. Pammel, L.A. 1911. A Manual of Poisonous Plants. Torch Press, Cedar toxic metabolites of Phoma sorghina, a new foliar pathogen of pokew~~,1. Mycologia 84:715-723. Rapids, IA. 289 p. 20. Watts, S. 1990. Engineered protein to tackle HIV. New Scientist 13. Pummel, L. H. 1912. Weeds of the Farm and Garden. Orange Judd Co., New 128( 1738):23. York. 281 p. 21. Zarling, J.M., P.A. Moran, 0. Haffar and others. 1990. Inhibition of HIV 14. Sauer, J. D. 1950. Pokeweed, an old American herb. Missouri Bot. Gard. by pokeweed antiviral protein targeted to CD4+ cells by monoclonal anti­ Bull. 38:82. bodies. Nature 347:92-95. 15. Sauer, J. D. 1952. A geography of pokeweed. Ann. Missouri Bot. Gard. 39:113-125.

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