Opuntia, also known as nopales or paddle cactus (see below), is a genus in the cactus family, Cactaceae. Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider a subgenus of Opuntia. Austrocylindropuntia, Corynopuntia, and Micropuntia are also often included in the present genus, but like Cylindropuntia, they seem rather distinct. Brasiliopuntia and Miqueliopuntia are closer relatives of Opuntia.
The most common culinary species is the Indian fig opuntia (O. ficus-indica). Most culinary uses of the term "prickly pear" refer to this species. Prickly pears are also known as tuna (fruit) or nopal (paddle, plural nopales) from the Nahuatl word nōpalli for the pads, or nostle, from the Nahuatl word nōchtli for the fruit; or paddle cactus.
Prickly pears typically grow with flat, rounded cladodes (also called platyclades) armed with two kinds of spines; large, smooth, fixed spines and small, hairlike prickles called glochids, that easily penetrate skin and detach from the plant. Many types of prickly pears grow into dense, tangled structures.
Like all true cactus species, prickly pears are native only to the Americas, but they have been introduced to other parts of the globe. Prickly pear species are found in abundance in Mexico, especially in the central and western regions, and in the Caribbean islands (West Indies). In the United States, prickly pears are native to many areas of the arid Western United States, including the lower elevations of the Rocky Mountains, where species such as Opuntia phaeacantha and Opuntia polyacantha become dominant, and especially in the desert Southwest. Prickly pear cactus is also native to the dry sandhills and sand dunes of the East Coast from Florida to Connecticut/Long Island (Opuntia humifusa). Further north, Opuntia occurs in isolated areas from the southern Great Lakes to southern Ontario. O. humifusa is also a prominent feature of the flora at Illinois Beach State Park, in Winthrop Harbor, Illinois, north of Chicago, and of Indiana Dunes State Park southeast of Chicago.
In the Galapagos Islands, six different species are found: O. echios, O. galapageia, O. helleri, O. insularis, O. saxicola, and O. megasperma. These species are divided into 14 different varieties; most of these are confined to one or a few islands. For this reason, they have been described as "an excellent example of adaptive radiation". On the whole, islands with tall, trunked varieties have giant tortoises, and islands lacking tortoises have low or prostrate forms of Opuntia.
The first introduction of prickly pears into Australia can be definitely ascribed to Governor Philip and the earliest colonists in 1788. Brought from Brazil to Sydney, they remained in Sydney, New South Wales, where they were rediscovered in a farmer's garden in 1839. The farmer's wife gave cuttings to neighbors and friends, who planted it not only in their gardens, but also as hedgerows. So began the Australian invasion that caused major ecological damage in the eastern states. They are also found in the Mediterranean region of Northern Africa, especially in Tunisia, where they grow all over the countryside, and southern Europe, especially on Malta, where they grow all over the islands, in the south-east of Spain, and can be found in enormous numbers in parts of South Africa, where it was introduced from South America.
Opuntia species are the most cold-tolerant of the lowland cacti, extending into western and southern Canada; one subspecies, O. fragilis var. fragilis, has been found growing along the Beatton River in central British Columbia, southwest of Cecil Lake at 56° 17’ N latitude and 120° 39’ W longitude. Prickly pears also produce a fruit, commonly eaten in Mexico, known as tuna; it also is used to make aguas frescas. The fruit can be red, wine-red, green, or yellow-orange.
Charles Darwin was the first to note that these cacti have thigmotactic anthers: when the anthers are touched, they curl over, depositing their pollen. This movement can be seen by gently poking the anthers of an open Opuntia flower. The same trait has evolved convergently in other cacti (e.g. Lophophora).
Chollas, now recognized to belong into the rather distinct genus Cylindropuntia, are distinguished by having cylindrical, rather than flattened, stem segments with the large barbed spines. The stem joints of several species, notably the jumping cholla (Cylindropuntia fulgida), are very brittle on young stems, readily breaking off when the barbed spines stick to clothing or animal fur as a method of vegetative reproduction. The barbed spines can remain embedded in the skin, causing discomfort and sometimes injury.
Growth (image gallery)
|Bud appears ►||Bud grows ►||Bud grows more►||Bud grows yet more►|
|Pad continues growth ►||Edible pad (tender) ►||Mature pad|
The fruit of prickly pears, commonly called cactus fruit, cactus fig, Indian fig or tuna in Spanish, is edible, although it must be peeled carefully to remove the small spines on the outer skin before consumption. If the outer layer is not properly removed, glochids can be ingested, causing discomfort of the throat, lips, and tongue, as the small spines are easily lodged in the skin. Native Americans, like the Tequesta, would roll the fruit around in a suitable medium (e.g. grit) to "sand" off the glochids. Alternatively, rotating the fruit in the flame of a campfire or torch has been used to remove the glochids. Today, parthenocarpic (seedless) cultivars are also available.
Cactus figs are often used to make candy, jelly, or drinks. The prickly pear fruit is also used as the main ingredient of a popular Christmas beverage in the British Virgin Islands, called "Miss Blyden".
Opuntia ficus-indica has been introduced to Europe, and flourishes in areas with a suitable climate, such as the south of France, southern Italy, Sicily (where they are referred to as fichi d'India or ficurinnia), and Sardinia (where they are called figumorisca - Moorish figs), along the Struma River in Bulgaria, in southern Portugal and Madeira (where they are called tabaibo, figo tuno or "Indian figs"), Andalusia, Spain ( where they are known as higos chumbos). In Greece, it grows in such places as the Peloponnese region, Ionian Islands, or Crete, and its figs are known as frangosyka (Frankish, i.e. Western European, figs) or pavlosyka (Paul's figs), depending on the region. In Albania, they are called fiq deti translated as 'sea figs', and are present in the south-west shore. The figs are also grown in Cyprus, where they are known as papoutsosyka or babutsa (cactus figs). The prickly pear also grows widely on the islands of Malta, where it is enjoyed by the Maltese as a typical summer fruit (known as bajtar tax-xewk, literally 'spiny figs'), as well as being used to make the popular liqueur known as bajtra. In Egypt, it is known as teen shouky. The prickly pear is so commonly found in the Maltese islands, it is often used as a dividing wall between many of Malta's characteristic terraced fields in place of the usual rubble walls. The prickly pear was introduced to Eritrea during the period of Italian colonisation between 1890 and 1940. It is locally known there as beles and is abundant during the late summer and early autumn (late July through September). The beles from the holy monastery of Debre Bizen is said to be particularly sweet and juicy. In Libya, it is a popular summer fruit and called by the locals Hindi, which literally means Indian.
In Morocco, Tunisia, Libya, Saudi Arabia, Jordan, and other parts of the Middle East, prickly pears of the yellow and orange varieties are grown by the side of farms, beside railway tracks and other otherwise noncultivable land. It is sold in summer by street vendors, and is considered a refreshing fruit for that season.
Tungi is the local St. Helenian name for cactus pears. The plants (Indian fig opuntia) were originally brought to the island by the colonial ivory traders from East Africa in the 1850s. Tungi cactus now grows wild in the dry coastal regions of the island. Three principal cultivars of tungi grow on the island: the 'English' with yellow fruit; the 'Madeira' with large red fruit; and the small, firm 'spiny red'.
The young stem segments, usually called nopales, are also edible in most species of Opuntia. They are commonly used in Mexican cuisine in dishes such as huevos con nopales (eggs with nopal), or tacos de nopales. Nopales are also an important ingredient in New Mexican cuisine.
In folk medicine and research
Most species of Opuntia contain a range of alkaloids in variable quantities, such as substituted phenethylamines. Identified compounds that may have biological activity include 3-methoxytyramine, candicine, and hordenine, as examples. The Sicilian prickly pear contains betalain, betanin, and indicaxanthin, with highest levels in their fruits.
Some species of Opuntia have been investigated in preliminary research. One study on O. megacantha raised concern about toxic effects on the kidney and extracts of O. streptacantha may inhibit alpha-glucosidase activity.
As an intoxicant
Mexican natives have used the food for thousands of years, to make colonche, an alcoholic drink. At least two commercially important distilled spirits are produced from Opuntia fruit. In Malta, the pink herbal bajtra liqueur is made from Opuntia. A St. Helenian distillery produces the clear, more potent Tungi Spirit from Indian fig opuntia cv. 'English' and 'Madeira'.
Opuntia is also added sometimes to the entheogenic drink Ayahuasca. Psychoactive compounds and derivates thereof have been confirmed in some species. These include 3,4-DMPEA, 4-hydroxy-3,5-DMPEA, and mescaline.
In dye production
Dactylopius coccus is a scale insect from which cochineal dye is derived. D. coccus itself is native to tropical and subtropical South America and Mexico. This insect, a primarily sessile parasite, lives on cacti from the genus Opuntia, feeding on moisture and nutrients in the cactus sap. The insect produces carminic acid, which deters predation by other insects. The carminic acid can be extracted from the insect's body and eggs to make the red dye.
Cochineal is used primarily as a red food colouring and for cosmetics. The cochineal dye was used by the Aztec and Maya peoples of Central and North America. Produced almost exclusively in Oaxaca, Mexico, by indigenous producers, cochineal became Mexico's second-most valued export after silver. The dyestuff was consumed throughout Europe, and was so highly valued, its price was regularly quoted on the London and Amsterdam Commodity Exchanges.
Now, the highest production of cochineal is by Peru, the Canary Islands, and Chile. Current health concerns over artificial food additives have renewed the popularity of cochineal dyes, and the increased demand is making cultivation of the insect an attractive opportunity in other regions, such as in Mexico, where cochineal production had declined again owing to the numerous natural enemies of the scale insect.
For earthen walls
For water treatment
The coat of arms of Mexico depicts a Mexican golden eagle, perched upon an Opuntia cactus, holding a rattlesnake. According to the official history of Mexico, the coat of arms is inspired by an Aztec legend regarding the founding of Tenochtitlan. The Aztecs, then a nomadic tribe, were wandering throughout Mexico in search of a divine sign to indicate the precise spot upon which they were to build their capital. Their god Huitzilopochtli had commanded them to find an eagle devouring a snake, perched atop a cactus that grew on a rock submerged in a lake. After 200 years of wandering, they found the promised sign on a small island in the swampy Lake Texcoco. There they founded their new capital, Tenochtitlan. The cactus (O. ficus-indica; Nahuatl: tenochtli), full of fruits, is the symbol for the island of Tenochtitlan.
The 1975–1988 version of the coat of arms of Malta also featured a prickly pear.
The prickly pear cactus ironically holds significance in both Palestinian and Israeli societies.
In Arabic, the cactus is called صبار ṣubbār; the related term sabr also translates to "patience" or "tenacity". The concept of sabr features prominently in the nonviolent resistance movement to Israeli military occupation. The prickly pear cactus represents the Palestinian struggle for freedom in both oral history and literature. Renowned Palestinian poet Mahmoud Darwish frequently uses the prickly pear cactus as a symbol of the Palestinian people in his work. Author Nadia Taysir Dabbagh compares the resilience of the cactus to that of the Palestinian people, writing, "The idea is that, even in an arid or harsh climate or environment, the Palestinians manage to go on living and surviving against all odds". The famous cartoon character Handala, created by Palestinian cartoonist Naji Salim al-Ali, takes his name from the prickly pear cactus, as handala is also another word for cactus in Palestinian culture. Handala is typically depicted with his back to the viewer; legend has it that he will only show his face once the Palestinians are free. The image of Handala was later adopted by the Popular Front for the Liberation of Palestine.
In Israel, the cactus fig is called tsabar (Hebrew: צבר) in Hebrew. This cactus is also the origin of the term sabra used to describe a Jew born in Israel. The allusion is to a thorny, spiky skin on the outside, but a soft, sweet interior, suggesting, though the Israeli sabras are rough and masculine on the outside, they are sweet and sensitive once one gets to know them.
The prickly pear cactus has been used for centuries both as a food source and a natural fence that keeps in livestock and marks the boundaries of family lands. They are incredibly resilient and often grow back.
The cactus lends its name to a song by British jazz/classical group Portico Quartet. The song "My Rival", on the album Gaucho by the American jazz-pop group Steely Dan begins with the words, "The wind was driving in my face/The smell of prickly pear."
In the fall of 1961, Cuba had its troops plant an 8-mile (13 km) barrier of Opuntia cactus along the northeastern section of the 28-kilometre (17 mi) fence surrounding the Guantanamo Bay Naval Base to stop Cubans from escaping Cuba to take refuge in the United States. This was dubbed the "Cactus Curtain", an allusion to Europe's Iron Curtain and the Bamboo Curtain in East Asia.
Prickly pears (mostly Opuntia stricta) were originally imported into Australia in the 18th century for gardens, and were later used as a natural agricultural fencing and in an attempt to establish a cochineal dye industry. They quickly became a widespread invasive weed, eventually converting 101,000 sq mi (260,000 km2) of farming land into an impenetrable green jungle of prickly pear, in places 20 ft (6.1 m) high. Scores of farmers were driven off their land by what they called the "green hell"; their abandoned homes were crushed under the cactus growth, which advanced at a rate of 1,000,000 acres (4,046.9 km2; 1,562.5 sq mi) per year. In 1919, the Australian federal government established the Commonwealth Prickly Pear Board to coordinate efforts with state governments to eradicate the weed. Early attempts at mechanical removal and poisonous chemicals failed, so in a last resort, biological control was attempted. The moth Cactoblastis cactorum, from South America, the larvae of which eat prickly pear, was introduced in 1925 and rapidly reduced the cactus population. The son of the noted entomologist Frederick Parkhurst Dodd, Alan Dodd, was a leading official in combating the prickly pear menace. A memorial hall in Chinchilla (Queensland) commemorates the moth.
The same moth, introduced accidentally further north of its native range into southern North America, is causing serious damage to some native species in that area.
Other animals that eat Opuntia include the prickly pear island snail and Cyclura rock iguanas. The fruit are relished by many aridland animals, chiefly birds, which thus help distribute the seeds. Opuntia pathogens include the sac fungus Colletotrichum coccodes and Sammons' Opuntia virus. The ant Crematogaster opuntiae and the spider Theridion opuntia are named for their association with prickly pear cacti.
- Opuntia aciculata – Chenille prickly pear , old man's whiskers, cowboy’s red whiskers
- Opuntia anacantha
- Opuntia atrispina
- Opuntia auberi
- Opuntia aurantiaca
- Opuntia basilaris – beavertail cactus
- Opuntia boldinghii
- Opuntia chaffeyi
- Opuntia chlorotica – pancake prickly pear; native to southwest USA and the Sonoran and Mojave deserts
- Opuntia clavata
- Opuntia cochenillifera
- Opuntia comonduensis
- Opuntia compressa
- Opuntia curvospina
- Opuntia decumana
- Opuntia decumbens – nopal de culebra
- Opuntia dejecta
- Opuntia echinocarpa
- Opuntia echios
- Opuntia elata
- Opuntia elatior Mill. – syn. O. bergeriana
- Opuntia engelmannii – Engelmann's prickly pear, cow's-tongue prickly pear, desert prickly pear, discus prickly pear, Texas prickly pear, calico cactus
- Opuntia erinacea
- Opuntia exaltata
- Opuntia excelsa
- Opuntia ficus-barbarica
- Opuntia ficus-indica – Indian fig opuntia
- Opuntia fragilis – little prickly pear, brittle cactus, found in the Great Plains and as far west as British Columbia
- Opuntia galapageia
- Opuntia gosseliniana – violet prickly pear
- Opuntia gosseliniana var. santa-rita – Santa Rita prickly pear
- Opuntia helleri
- Opuntia hickenii
- Opuntia humifusa – eastern prickly pear (sometimes included in O. compressa)
- Opuntia hyptiacantha
- Opuntia inamoema K. Schum. – quipá
- Opuntia insularis
- Opuntia invicta
- Opuntia jamaicensis
- Opuntia laevis
- Opuntia lasiacantha
- Opuntia leucotricha – arborescent prickly pear, Aaron's beard cactus, semaphore cactus, Duraznillo blanco, nopal blanco
- Opuntia lindheimeri – cowtongue prickly pear
- Opuntia littoralis – coastal prickly pear, sprawling prickly pear
- Opuntia longispina
- Opuntia macrocentra – black-spine prickly pear, purple prickly pear, found in southwest USA and northern Mexico
- Opuntia macrorhiza – Plains prickly pear, found throughout the Great Plains except for the northernmost areas (not found in North Dakota), and extending sporadically eastward as far as Kentucky, syn. O. leptocarpa MacKensen, O. tenuispina Engelm., O. tortispina Engelm. & Bigelow
- Opuntia matudae – xoconostle (syn. Opuntia joconostle)
- Opuntia maldonandensis
- Opuntia maxima
- Opuntia megacantha
- Opuntia megarrhiza
- Opuntia microdasys – bunny ears cactus, polka-dot cactus
- Opuntia monacantha – common prickly pear
- Opuntia oricola
- Opuntia ovata
- Opuntia paraguayensis
- Opuntia phaeacantha – tulip prickly pear, includes plateau prickly pear, brown-spined prickly pear, Mojave prickly pear, Kingman prickly pear
- Opuntia pinkavae – Pinkava's prickly pear
- Opuntia polyacantha – Panhandle prickly pear, found in the Great Plains, Great Basin, Mojave Desert, Colorado Plateau, and the Rocky Mountains, syn. O. rhodantha K.Schum.
- Opuntia pubescens (syn. O. pascoensis Britton & Rose)
- Opuntia pusilla – creeping cactus, syn. O. drummondii Graham
- Opuntia quitensis – Red Buttons opuntia (syn. O. macbridei, O. johnsonii, Platyopuntia quitensis)
- Opuntia rastrera
- Opuntia repens
- Opuntia robusta
- Opuntia rufida (sometimes included in O. microdasys)
- Opuntia schumannii
- Opuntia soehrensii
- Opuntia stenopetala (syn. O. riviereana Backeb.)
- Opuntia streptacantha
- Opuntia stricta – erect prickly pear, spineless prickly pear
- Opuntia subulata – found in South America
- Opuntia sulphurea
- Opuntia taylori
- Opuntia tehuantepecana – nopal de caballo
- Opuntia tomentosa – woollyjoint prickly pear
- Opuntia triacantha
- Opuntia tuna
- Opuntia velutina
- Opuntia violacea
- Disocactus phyllanthoides (as Opuntia speciosa)
- Rebman, Jon P. "What has happened to Opuntia?". San Diego Natural History Museum.
- Quattrocchi, Umberto (2000). CRC World Dictionary of Plant Names. III M-Q. CRC Press. p. 1885. ISBN 978-0-8493-2677-6.
- Fitter, Fitter, and Hosking, Wildlife of the Galapagos (2000)
- Patterson, Ewen K. 1936. The World's First Insect Memorial. "The Review of the River Plate", December pp. 16–17
- Cota-Sánchez (2002)
- Originally meaning "Native American", though the specific epithet, "ficus-indica", means "fig from India". Note also Ficus benghalensis which is both a true fig tree and from South Asia.
- Grigson, Jane. Jane Grigson's Fruit Book, 2007, U of Nebraska Press, p. 380. ISBN 0-8032-5993-X
- Midey, Connie (May 31, 2005). "A magical plant". The Arizona Republic. Retrieved May 22, 2010.
- Jarman, Max (October 11, 2005). "Hand crafted hooch: Prickly pear vodka from Flagstaff". The Arizona Republic. Retrieved May 22, 2010.
- Gist, Wendy (May 2009). "Southwest Flavor: Stick to It". New Mexico Magazine. Retrieved May 22, 2010.
- Butera, Daniela; Luisa Tesoriere, Francesca Di Gaudio, Antonino Bongiorno, Mario Allegra, Anna Maria Pintaudi, Rohn Kohen, and Maria A. Livrea (2002). "Antioxidant activities of sicilian prickly pear (Opuntia ficus indica) fruit extracts and reducing properties of its betalains: betanin and indicaxanthin". Journal of Agricultural Food Chemistry 50 (23): 6895–6901. doi:10.1021/jf025696p. PMID 12405794.
- Jaime Becerra-Jiméneza, Adolfo Andrade-Cettob,"Effect of Opuntia streptacantha Lem. on alpha-glucosidase activity" Journal of Ethnopharmacology Volume 139, Issue 2, 31 January 2012, Pages 493–496
- Nyerges, Christopher. "Prickly Pear Cactus". Wilderness Way 6 (2).
- Frati AC, Xilotl Diaz N, Altamirano P, Ariza R, Lopez-Ledesma R."The effect of two sequential doses of Opuntia streptacantha upon glycemia"(1991)
- Bajtra (Bajtra Liqueur official site)
- Ott (1995)
- Confirmed in Opuntia exaltata: Trenary (1997)
- Confirmed in Opuntia basilaris, O. exaltata: Trenary (1997)
- Confirmed in Opuntia basilaris (.01%), O. ficus-indica, O. invicta: Trenary (1997)
- Behan (1995)
- Portillo M. & Vigueras G. (1988)
- Spinner, Kate. "Desert cactus has secret talent for purifying water". Sarasota Herald-Tribune. Retrieved 30 November 2013.
- O'Brien, Miles. "Cactus "flesh" cleans up toxic water". National Science Foundation. Retrieved 30 November 2013.
- Tamir, Tally (1999). "The Shadow of Foreignness: On the Paintings of Asim Abu-Shakra". Palestine-Israel Journal 6 (1).
- http://books.google.jo/books?id=SbzIAAAAQBAJ&pg=PA41&dq=palestine+sabr&hl=en&sa=X&ei=c2IGU52JDuTb7Aahg4HoDw&redir_esc=y#v=onepage&q=palestine%20sabr&f=false. Missing or empty
- http://books.google.jo/books?id=3H9b8DJK4bAC&pg=PA78&lpg=PA78&dq=palestine+sabr&source=bl&ots=DQtB0Yg_Ig&sig=vhSoTk0MeD9bPBjJC7B00_vJ74U&hl=en&sa=X&ei=jV8GU5OfKo6p7AbKyYDQAQ&redir_esc=y#v=onepage&q=palestine%20sabr&f=false. Missing or empty
- Almog, Oz. 2000. The Sabra the creation of the new Jew. The S. Mark Taper Foundation imprint in Jewish studies. Berkeley: University of California Press
- Over here and over there. The Economist, 2006-NOV-16. Retrieved 2007-OCT-16.
- "LYRICS | GAUCHO (1980)". Steely Dan.
- "Guantanamo Bay Naval Base and Ecological Crises". Trade and Environment Database. American University. Retrieved 2009-04-19.
- "Yankees Besieged". TIME. 1962-03-16.
- Griffith, M. P. (2004). "The origins of an important cactus crop, Opuntia ficus-indica (Cactaceae): New molecular evidence". American Journal of Botany 91 (11): 1915–1921. doi:10.3732/ajb.91.11.1915.
- Behan, Jeff (1995): The bug that changed history. Boatman's Quarterly Rreview 8(2). HTML fulltext
- Bwititi, P.; Musabayane, C.T. & Nhachi, C.F.B. (2000): Effects of Opuntia megacantha on blood glucose and kidney function in streptozotocin diabetic rats. Journal of Ethnopharmacology 69(3): 247–252. doi:10.1016/S0378-8741(99)00123-3 PMID 10722207 (HTML abstract)
- Cota-Sánchez, J. Hugo (2002): Taxonomy, distribution, rarity status and uses of Canadian Cacti. Haseltonia 9: 17–25 Google Scholar PDF abstract
- Frati-Munari, A.C.; Fernandez-Harp, J.A.; de la Riva, H.; Ariza-Andraca, R. & del Carmen Torres, M. (1983): Effects of nopal (Opuntia sp.) on serum lipids, glycemia and body weight. Archivos de investigacion medica 14(2): 117–125. PMID 6314922 [Article in English, Spanish]
- Ott, Jonathan (1995): In: Ayahuasca Analogues: Pangaean Entheogens.
- Pittler, Max H.; Verster, Joris C. & Ernst, Edzard (2005): Interventions for preventing or treating alcohol hangover: systematic review of randomised controlled trials. Brit. Med. J. 331(7531): 1515–1518. doi:10.1136/bmj.331.7531.1515 PMID 16373736 PDF fulltext Nopalea
- Portillo M., Liberato & Vigueras G., Ana Lilia (1988): Natural Enemies of Cochineal (Dactylopius coccus Costa): Importance in Mexico. Journal of the Professional Association for Cactus Development 3: 43–49. PDF fulltext
- Rayburn, Keith M.D.; Martinez, Rey; Escobedo, Miguel; Wright, Fred & Farias, Maria (1998): Glycemic Effects of Various Species of Nopal (Opuntia sp.) in Type 2 Diabetes Mellitus. Texas Journal of Rural Health 16(1): 68–76.
- Trenary, Klaus (1997): Visionary Cactus Guide: Opunita [sic]. Retrieved 2007-OCT-15.
- Wiese, Jeff; McPherson, Steve; Odden, Michelle C. & Shlipak, Michael G. (2004): Effect of Opuntia ficus indica [sic] on Symptoms of the Alcohol Hangover. Arch. Intern. Med. 164(12): 1334–1340. PDF fulltext
- For a list of USA species see: "Opuntia Web"