Opuntias are a vast and varied group. They grow on every continent except Antarctica. Prickly pears interact with animals and are used as animal fodder; are affected by the weather; are eaten for food, vitamins, and overall health; and even provide a red dye. These articles will help you find out more about opuntias. Prickly pears are important weeds in some dry areas such as southern Africa or Australia, but they are also managed as crops on some continents.
Although you might think Opuntia names name would be simple, Opuntia or prickly pear cactus. It turns out that there are a multitude of names for just one Opuntia, O. ficus-indica, including:
Barbary Fig, Cactus decumanus, Cactus ficus-indica, Cactus Flowers, Cactus Fruit, Cactus Pear Fruit, Figue d’Inde, Figuier de Barbarie, Fruit du Cactus, Fruit de l’Oponce, Indian Fig, Indian Fig Prickly Pear, Indien Figue, Nopal, Nopal Cactus, Nopales, Nopol, OPI, Oponce, Opuntia, Opuntia albicarpa, Opuntia amyclaea, Opuntia cordobensis, Opuntia decumana, Opuntia ficus, Opuntia ficus-barbarica, Opuntia ficus-indica, Opuntia gymnocarpa, Opuntia hispanica, Opuntia joconostle, Opuntia maxima, Opuntia megacantha, Opuntia paraguayensis, Prickly Pear, Spineless Cactus, and Tuna Cactus.
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Reproduction, DNA biology, and ecology are powerful drivers of Opuntia biology. Knowledge of these topics will help us understand opuntias. The genetics, biology, and speciation of Opuntia are poorly understood. In fact, opuntias remain a poorly studied group overall except for O. ficus-indica. This latter species is much studied. However, most of the information about O. ficus-indica relates to crop production, and it is difficult to apply crop production principles to derive basic principles.
There are relevant publications about Opuntia reproduction and ecology. Our goal with this page is to provide access to some of the literature that does exist. This collection illuminates some areas of Opuntia biology, but also raises other questions. For instance, why is polyploidy common in the genus? What factors control hybridization? How do species remain stable in the face of sympatry?
We also provide a number of articles on general principles in plant biology as they relate to various topics. For instance, an article that generally discusses plant speciation can provide insight to processes that may occur in opuntias
Opuntias are an amazing group of plants that have successfully adapted to hostile environments. They share many features with other cacti, but they have unique anatomies and some grow where other cacti do not (e.g., the eastern United States). We hope these articles help you appreciate them even more.
Multiple references were consulted during the construction of this prickly pear website–Opuntia Web. There are countless confusing references about cacti in general and opuntias in particular; there are often many names that refer to the same species of cactus. We worked our way through them to decide Opuntia names. Generally, we chose names that are associated with good descriptions or which are names of longstanding–or both. The names we chose provide a good starting place for the reader if they want to look up more names. For instance, O.humifusa was called O. opuntia by Britton and Rose, but this name fell into disuse. Later, it was called O.compressa, and this name fell into disuse. At one time in the early 1800s O.humifusa was known as Cactushumifusus. Perhaps any of these names could be used, but we chose O.humifusa.
An important part of a plant name is the person who named it, and the journal and year it was published. For instance, the long-form name of O.humifusa is “Opuntiahumifusa (Rafinesque) Rafinesque, Flora Medica (or Manual of the Medical Botany of the United States of North America) 2: 247, 1830.” This long name tells you that the author was Constantine Samuel Rafinesque. The name was published in Flora Media, volume 2 on page 247 in 1830.
Names make a difference. If you use O.humifusa, you will never find the writings about Cactus humifusus and you will miss important information. We present some of those references here so you can consult them for yourselves. You may decide to choose a name that we passed over, but these resources will help you find other names.
On the other hand, for just gardening and enjoying plants, names are not so terribly important. O.humifusa is also known as O. compressa and most Opuntia growers know they are the same plant. Sometimes people describe a plant with a name such as, “the cactus from my grandmother that has yellow flowers.” This is fine for informal purposes.
If you want more information, consult the resources listed here. We also hope you will write to us if you have questions about names or for any other reason. Perhaps you will have a suggestion about a better name choice than we made.
The Cactaceae: Descriptions and Illustrations of Plants of the Cactus Family was provided courtesy of the Cactus and Succulent Digital Library The PDF copy that we use has been pass through optical character recognition and manually checked. Our thanks to the CSDL.
Ploidy information for many Opuntia species of the USA may also be found in “Pricklypears Commonly Found in the United States and Northern Mexico”, Green, C with Ferguson, D, 2012 (ISBN: 0615131212, 9780615131214). Another excellent source of ploidy information for cacti is “Cacti of the Trans-Pecos and Adjacent Areas”, Powell and Weedin, 2004 (ISBN: 0896725316, 978-0896725317).
Prickly pear names change, and new science provides new evidence. Ploidy levels and taxonomy as presented here represent the best knowledge available at the time the various materials were published. Some species were undoubtedly misidentified. Names of opuntias have changed over time, thus it is important to interpret this information carefully.
Louis Charles Christopher Krieger (1873-1940) worked with David Griffiths at the Plant Introduction Garden in Chico, California. Griffiths was interested in the forage potential of prickly pear cacti (Opuntia spp.).
Krieger painted a large series of species and forms of Opuntia between 1912 and 1917 for Griffith’s studies. These paintings are in the collection of the Department of Botany, Smithsonian Institution. They are watercolor over light photographic prints (black and white). The attention to anatomical and morphological detail is exquisite.
Krieger painted many cacti, and his work is found in The Cactaceae, an important series by Britton and Rose. Though he is featured here for his Opuntia paintings, he is best known for his depictions of fungi.
Mary Emily Eaton (1873-1961) was born on 27 November 1873 in Coleford, Gloucestershire, England. She is best known as a botanical artist for her illustrations in The Cactaceae (Britton and Rose, 1919-1923) for which she was the principal illustrator.
She was employed by the New York Botanical Garden from about 1911 to 1932. Her illustrations are housed at the National Geographic Magazine and in the Contributions from the U.S. National Herbarium. These drawings of various opuntiads are from The Cactaceae, v1. Full-size drawings are available at Plant Illustrations.
The first iteration of Opuntia Web was built in 2005. Our scientists identified Opuntia species in the field. We visited the western states to study cacti in habitat. We also visited Florida, the southern Atlantic states, and the Midwest to observe cacti in those regions (e.g., O.macrarthra). We made a visit to Pennsylvania to verify the presence of O.humifusa. In addition to extensive field studies, we consulted herbarium specimens, old black and white photographs, compendia, the current literature, original citations and descriptions.
We compared our field observations of opuntias with the information we found from these sources to identify the plants that we observed. Additionally, we consulted with other specialists and scientists on an ad hoc basis. Herein, we provide evidence to support our findings in the form of descriptions, published literature, photo-reproductions of herbarium samples, and in situ photographs. Opuntia Web does not provide new taxonomic decisions. Rather, it uses published descriptions of species and identifies the plants in the field. Taxonomy is a separate discipline from identification of plants with published materials.
Our understanding of Opuntia continues to evolve, and there are many names available for some species. A single citation is used herein to provide an Opuntia species name. The precise citation chosen provides the earliest identifying name for the taxon as we treat it and a place for the reader to start if more information is desired. Tropicos is a good place to expand the search for alternate treatments.
We anticipate that some names will change in the future. We also understand that currently undescribed taxa will be reported in the future. We will change our treatments accordingly as new Opuntia information is published. For instance, one of our editors (Nancy Hussey) recently co-published the description of O.diploursina with her colleagues.
Some species of Opuntia have been lost to science because they were assumed to be synonymous with other taxa. For instance, O.cespitosa was lost because it was assumed to be synonymous with O.humifusa. However, more recently, botanists have shown O.cespitosa to be separate and distinct from O.humifusa. Likewise O.mesacantha ssp. mesacantha and O.mesacantha ssp. lata were assumed to be synonymous with O.humifusa but are now known to be different. Thus, there are four species known were it was thought there was only one.
What is a species?
Identification of an Opuntia species requires a working sense of what a species is. We use the following considerations as our guide, “clusters of monotypic or polytypic biological entities, identified using morphology, genetics, or molecular biology, forming groups that have few or no intermediates with other groups when in contact.” We also accept that Opuntia species are “groups of organisms that inherit characters from each other…and are a reproductive community and unit.”
We know that future phylogenetic hypotheses supported by molecular comparisons and rigorous morphometric and ecological analyses (see the treatment of O.humifusa s.l.) will supplement our current observations and help further illuminate our knowledge of opuntias. Field studies of Opuntia species will also be essential for our understanding and we will adapt and change this Website to reflect new findings.
We consider varieties as populations within a species that differ from the type in some details and that blend into one another anywhere their distributions meet or overlap. It is often difficult to label an Opuntia type to a proper variety because, unlike hybrids, varietal intermediates may occur with regularity and may be only subtly different from the type. Our thought is that widespread and variable Opuntia species (e.g., O.phaeacantha or O.engelmannii) may contain undescribed varieties or even subspecies and species. For example O. gregoriana is now considered to be a form of O.engelmannii, but it was once treated as a separate species. However, perhaps it could be described as a variety?
We consider gross morphological information of opuntias such as spine colors, sizes, numbers, and arrangements, etc; glochid arrangements, sizes, and colors; cladode shape, color, and overall aspect; areole details; fruit and seed characteristics, general plant appearance, size, and shape; etc. Even edaphics, elevation, geography, and climate are considered as we identify species. Sometimes Opuntia bloom season is considered. If observable, we also consider phenotypic clines, introgressions, and other types of data in making decisions about the limits of a taxon. Ploidies are determined by our Editor-in-Chief or are reported in the literature.
Other data, such as phenology; pollination ecology; ecosystem position, and proposed phylogenies, etc., are mostly not available for opuntias at the specific level. However, where published such information is used to inform our treatments and descriptions of opuntias.
Because opuntias are notoriously plastic in gross morphology, we do not rely upon single plants, observations, or locations, etc., to inform our decisions. Rather, we observe multiple plants, in multiple locations, under different conditions, and over different seasons to make determinations.
Opuntia is a dynamic genus, and hybridization, polyploidy, and introgression are important biological processes that affect opuntias as well as our understanding of them.
Opuntiahybrids do occur, but they are not the norm even though they can be confusing. Given the abundance of Opuntia species, the sheer number of individual plants and their overlapping ranges, there are actually few hybrids observed in Nature. When they do occur they are generally found in hybrid zones or regions where two Opuntia species overlap. Even in such zones, Opuntia hybrids are the exception. Because they are exceptions, and may have unique features, hybrids are often prized in gardens.
Polypoidization occurs in Opuntia. The basic chromosome number for Opuntia is 11 (2N = 22) However, many Opuntia species are polyploid; they may be tetraploid (2N = 44), hexaploid (2N = 66), or even octaploid (2N = 88). Triploid (N = 3X) and pentaploid (N = 5X) plants are known, but their contributions to gene exchange are unknown.
Polyploidy may mask entities that are apparently identical, but which actually have different ploidies. For instance, there are diploid, triploid, and tetraploid examples of O.pusilla. Similarly, there are diploid and tetraploid examples of O.humifusa s.l. Auto- and allopolypoidy occurs in Opuntia, and such rich genetic resources have created wonderfully varied species.
Introgression occurs in Opuntia species. Introgression is different from hybridization because it refers to the transfer of limited genetic information from one species to another through ancient hybridization and repeated backcrossing. Introgression begins with hybridization, but it is so much more. Hybridization may split two genomes equally, whereas introgression is generally the invasion of a few genes into one of the parents–leaving the species essentially the same as before.
Introgression is a ubiquitous phenomenon in plants and animals and it contributes to adaptation. Modern humans are an example of an introgressed species because many of us carry some genes from Neanderthal humans. An example of introgression in Opuntia might be a pink-flowered population in a species that is generally yellow flowered.
Opuntiaengelmannii and O.lindheimeri, are similar prickly pears, but there are also constant differences between these prickly pear cacti. We accept these opuntias as separate and distinct species. However, O.lindheimeri has been described as a variety of O.engelmannii by some authors. However you think of them (one Opuntia species or two), this checklist describes the differences.
The younger pads of O.lindheimeri are less woody and “softer” or “greener” in appearance. Thus, the two opuntias appear different in overall aspect.
O.engelmannii spines range from white, to tan, to yellow shades and brownish. O.engelmannii spines are seldom a rich canary yellow or shiny yellow. O.lindheimeri spines are almost always shiny yellow, whereas O.engelmannii spines are chalky and if yellow are dull.
The base of O.engelmannii spines may be brown, or blackish, or even dark red-brown. Occasionally, plants are found with spine bases that are not darker than the spines. In contrast, the base of O.lindheimeri spines are seldom true brown or black but may be red-brown, dark plum, rust-brown, pink shades, or dark yellow.
The annular markings of O.lindheimeri spines are more apparent than in O.engelmannii. The markings may not even be observable in O.engelmannii.
O.lindheimeri fruits are narrower at the base or even vaguely pear-shaped; they tend to have a smooth surface and are typically red when newly ripe. O.engelmannii fruits are oval or roundish, darker (more purple or black-red) and less clear red in color, and with a more rugose (bumpy) surface. The umbilicus of O. engelmanni fruits is usually more depressed into the end of fresh fruit.
O.engelmannii fruits are sweet and pleasant tasting, whereas those of O.lindheimeri are sour and not sweet. O.lindheimeri fruits are sometimes almost noxious.
Plants with orange or red flowers occur occasionally (not often) in O.lindheimeri but are rare in O.engelmannii. Yellow flowers of either species may change to orange shades late in the day of anthesis or on the day after. Thus, the flower colors of these two opuntias can be different.
O.lindheimeri is primarily a plant of Texas east of the Pecos River (extending into LA). In contrast, O.engelmannii is typically found west of the Pecos River to CA. If west of the Pecos River, O.lindheimeri grows in more mesic conditions than O. englemannii such as valley bottoms or partially shaded slopes.
We are a group of botanists that enjoys writing about and photographing Opuntia and related plants. We enjoy studying them in the field and growing them in our gardens. We hope you enjoy reading about them.
Write to us. We are always happy to hear from others if there is a point we have not considered or if we have made an error. Such input will only make this Website better.
Joe J. Shaw, PhD ELS, Publisher and Executive Editor
Joe is a botanist and a plant pathologist, and he is a former associate professor of Botany. He grew up in the West and spent much time studying plants there. As publisher he builds the Opuntia Website and organizes the content. Joe writes most of the Website and provides many of the photos. He works with the other editors to get Opuntia photo IDs correct before publishing them online. Joe still travels throughout the West to study plants and to consult with other scientists.
David J. Ferguson, Curator Rio Grande Botanic Garden, Albuquerque, NM, Executive Editor and Senior Scientific Editor
Dave is our taxonomist, and he has the nearly impossible job of making sure all Opuntia photographs are correctly identified. He is also curator of the Rio Grande Botanic Garden in Albuquerque, NM. Dave has many years experience exploring North and South America to study Opuntia, other cacti, and other types of plants. Dave is a published author of multiple books and papers about cacti including Pricklypears Commonly Found in the United States and Northern Mexico. He is also referenced in multiple cactus-related publications, e.g., “Cacti of the Trans-Pecos & Adjacent Areas” (AM Powell and JF Weedin, 2004, Texas Tech University Press).
Nancy Hussey, Editor for the Mojave Desert
Nancy has grown plants and studied them for many years; she has the difficult task of keeping tabs on the Mojave Desert and its Opuntia species. The Mojave Desert is home to some poorly documented and rare species. Additionally, Nancy has the largest Opuntia garden in northern Arizona. She grows her plants just the way Nature would, with no extra water or fertilizer. The plants look just like they do in the wild, and she provides many photographs of hard-to-find plants. Moreover, Nancy is co-discoverer of O.diploursina. Finally, Nancy is our beta tester for software, site changes, and theme updates.
Daniel A. Green, Editor for Florida
Danny is our Florida botanist and ecologist. He is responsible for identifying the many Opuntia species in that state including some that are difficult to find and some that are very poorly understood. Danny is an outdoor kind of guy and he especially enjoys locating, studying, and photographing hard-to-find plants, including rare Florida opuntias.
The Other Stuff
Most photos were taken by the publisher or the editors, and most were taken in habitat with the goal of showing their natural state. Some Opuntia plants were photographed in gardens. Some plants were photographed by others, and photographer credits are provided.
Special Photo Contributor
Derrill Pope provided multiple photographs of flowers. Contact him at Flower Mountain Nursery if you would like to buy cacti (FaceBook or email: [email protected]).
We accept advertisements. We earn a small amount from them ($30 in the first 8 months of 2019). Out goal is to earn enough to pay part of the costs of running this website, which costs about $300 per year to operate. We are far from that goal.
All rights are reserved. For purely, fully, strictly, and explicitly nonprofit use, we are happy to share in most cases; just write to us. Some Opuntia photographs and related text belong to others and they must be contacted individually to obtain permissions. All materials originally published before 1925 may be used freely as is the case with government publications.
We strive to provide accurate information, but errors may occur. We (all persons providing content, photographs, ideas, information, or commentary herein) are not responsible for any confusion, ill effects, damages, or losses resulting from use or interpretation of any materials or information herein.
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