General Opuntia Topics

Grilled Nopales
Grilled Nopales

Opuntia topics

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. 



General Information

Special Topics

Food and Medicine



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Our website address is: https://www.opuntiads/*. Read about us at the About page

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Opuntia Biology

Opuntia in Habitat
Opuntia in Habitat

Biology is Important

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. 

The Publications

A cyclical relationship between Larrea tridentata and Cylindropuntia leptocaulis

A diffusion model for dispersal of Opuntia imbricata

A flora of southern Arizona–Cactaceae

A genomic view of introgression and hybrid speciation

Arbuscular mycorrhizal fungal status of Opuntia humifusa

A micromethod for recovery of DNA from Opuntia ficus-indica

Breaking seed dormancy in Opuntia rastrera

Cacti–biology and uses


Opuntia Glochid Tufts
Opuntia Glochid Tufts

Cactus insects of the USA

Cactus seed germination – a review

Chromosomes of Opuntia

Cytogeography of the humifusa clade of Opuntia

DNA arithmetic calculator

Endozoochorous dispersal of Opuntia seeds

Establishment of a micromethod for recovery of DNA from Opuntia ficus-indica for RAPDs

Evidence for hybridization and introgression within a species-rich community oaks

Effect of environmental heterogeneity on Opuntia germination

Effect of fungi on the germination of Opuntia

Genetics of Opuntia production in Mexico

Genome characterization of Opuntia ficus-indica

Germination of hard seed-coated Opuntia tomentosa

Germination responses of Opuntia spp. to temperature

Germination of Opuntia

Genome characterization of Opuntia ficus-indica

Gibberelins in Opuntia


Opuntia Pollen
Opuntia Pollen

Hardy-Weinberg equation

Hardy-Weinberg and alleles

Heterochrony and its role in sex determination of cryptically dioecious Consolea flowers

Hybrid speciation in plants

Hybridization and speciation

Hybridization, introgression, and the nature of species boundaries

The use of multivariate analysis of karyotypes to determine relationships between species of Opuntia

Insect pollination of prickly pears (Opuntia–Cactaceae)

Intriguing thigmonastic (sensitive) stamens in the Plains Prickly Pear Opuntia polyacantha (Cactaceae)

Karyotypic studies in Opuntia

Low levels of genetic differentiation between Opuntia echios varieties

Micro-method for genome characterization of Opuntia

Mixed reproduction systems in Opuntia monacantha

Molecular based assessment of genetic diversity of xoconostle

Molecular based assessment of genetic diversity within Barbary fig

Molecular characteristics of prickly pear cactus in Mexico


Opuntia orbiculata fruit
Opuntia fruit

Molecular studies of forage prickly pear cactus from Brazil

Morphological and structural study of Opuntia seeds

Morphological seeds descriptors for characterize and differentiate genotypes of Opuntia (Cactaceae, Opuntioideae)

Mountain scrublands, economy, social systems, and Opuntia in Peru

Multiple explanations for the elevated diversification of cacti in the New World Succulent Biome

Mycoflora in exhumed seeds of Opuntia tomentosa and its possible role in seed germination

Mycorrhizal associations in Opuntia humifusa in in Illinois

Nectaries on Cylindropuntia acanthocarpa

Nematodes as a possible cause of damage to Opuntia ficus-indica

Notes on the cochineal insect

Opuntia chromosomes

Opuntia cymochila–a species lost in the shuffle

Opuntia Stomate
Opuntia Stomate


Opuntia in Mexico–identifying priority areas for conserving biodiversity in a multi-use landscape

Opuntia polyacantha creates refuges for other plants

Prickly coexistence or blunt competition–Opuntia refugia in a rodent community

Phylogeny of the Opuntioideae

Phylogenetic relationships and evolution of growth form in Cactaceae

Phylogenetic relationships and morphological evolution in Opuntia s.str.

Phylogenetic Relationships in Opuntia from Southern South America

Phylogenetic relationships in the cactus family (Cactaceae) based on evidence from trnK/matK and trnL-trnF sequences

Phylogeny of Opuntia–clade delineation, geographic origins,  and reticulate evolution

Physio-ecological study of the jumping cholla, C. fulgida

Physiology of Opuntia and nurse plants

Phytoplasma associated with abnormal proliferation of Opuntia cladodes

Pigment evolution in the Caryophyllales–a systematic overview

Plains prickly pear  response to fire

Plant biological warfare–thorns inject pathogenic bacteria into herbivores

Plant sex determination and sex chromosomes

Plant speciation through chromosome instability and ploidy change–evolutionary relevance

miRNA expression during prickly pear cactus development


Opuntia blakeana cladode
Opuntia cladode

Plant speciation

Pollen grain characters of certain Cactaceae

Pollen morphology and reproductive performances in Opuntia ficus-indica

Polymorphisms in microsatellite markers in Opuntia of the Gallapagos Islands

Population dynamics of Cacti

Reproductive biology of Consolea spinosissima

Role of micromorphological leaf traits and molecular data in Oak studies

Serendipitous backyard hybridization and the origin of crops

Pollen morphology and reproductive performances in Opuntia ficus-indica

Pollination biology of Opuntia imbricata

Pollination of  Opuntia lindhemeri and related species

Pollination of the southwestern Opuntias

Polinator generalists of Opuntia sulphurea

Population dynamics of Opuntia macrorhiza

Reproductive Isolation in fragmented wild populations of Opuntia streptacantha

Reproductive biology of Opuntia

Reproductive Ecology of Opuntia macrocentra

Seed germination of Opuntia species from an aridity gradient in Central Mexico

Seed predation and dispersal in a dominant desert plant Opuntia, ants, birds, and mammals

Seed predation of two alien Opuntia species invading Mediterranean communities

Seed banks of Opuntia rastrera

Vertebrate frugivory and seed dispersal in Opuntia

Seed dormancy in Opuntia rastrera

Seed germination in Opuntia streptacantha

Scanning electron microscopy of Opuntia pollen

Stamen movements in flowers of Opuntia favor certain insects

Stimulation and promotion of germination of Opuntia ficus-indica

Storm-driven ocean dispersal of Opuntia

The effect of different amounts of cladode removal on reflowering of cactus pear


New Leaves on Opuntia
New Leaves on Opuntia

Stamen movements in flowers of opuntia

Scanning electron microscopy of Opuntia pollen

Sprouting flower buds of Opuntia

Spreading of Opuntia in overgrazed pastures in Kansas

The Fertilization of Opuntia

The Fruit of Opuntia

The Importance of Opuntia in Mexico and Cactoblastis invasion

The pollination spectrum of the southwestern cactus flora

The Role of Hybridization in plant speciation

The origins of an important cactus crop, Opuntia ficus-indica

The role of native flower visitors in pollinating Opuntia ficus-indica (L.) Mill., naturalized in Sicily

The Hardy-Weinberg principle

The use of multivariate analysis for karyotypes opuntia

Opuntia References

Opuntia oricola
Opuntia oricola


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 Cactus humifusus. 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 “Opuntia humifusa (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. 

See in this Website


DNA, Reproduction, and Ecology

How Species Are Identified

Other Sources

A Dictionary of Botany, Little, RJ and Jones, EU, Van Nostrand Reinhold Co, 1983

Biodiversity Heritage Library, Website

Botanicus, Website

Cacti & Other Succulents of Arizona (Field Guide to), Breslin, P et al, Tucson Cactus and Succulent Society,  2015

Cacti of Texas and Neighboring States, Weniger D, University of Texas Press, second ed, 1988

Cacti of the Southwest, Del Weniger, University of Texas Press, 1978

Cacti of the Trans-Pecos and Adjacent Areas, Powell MA and Weedin JF, Texas Tech University Press, 2004 

Cacti, Agaves, and Yuccas of California and Nevada, Ingram, S, Cachuma Press, 2008

Cacti, Biology and Uses, Park S Nobel (ed), 2002, University of California Press

Cactiguide, Website

Cactus and Succulent Digital Library, Website

Chromosome Counts Database, Website

Field Guide to Cacti & Other Succulents of Arizona, Breslin et al., 2015

Flora of North America, Website

Index to Plant Chromosome Numbers, Website

Opuntia toumeyi
Opuntia toumeyi

Opuntia at American Southwest, Website

Opuntia at Encyclopedia Britannica. Website

Opuntia at Encyclopedia of Life, Website

Opuntia at Gardenia Net, Website

Opuntia, at Wikipedia, Website

Pricklypears commonly found in the United States and northern Mexico, Green, C with Ferguson, D, 2012

The Cactaceae: descriptions and illustrations of plants of the cactus family, NL Britton and NJ Rose, Carnegie Institution of Washington, volume 1, 1919

The Cactaceae: descriptions and illustrations of plants of the cactus family, NL Britton and NJ Rose, Carnegie Institution of Washington, volume 2, 1920

The Cactaceae: descriptions and illustrations of plants of the cactus family, NL Britton and NJ Rose, Carnegie Institution of Washington, volume 3, 1922

The Cactaceae: descriptions and illustrations of plants of the cactus family, NL Britton and NJ Rose, Carnegie Institution of Washington, volume 4, 1923

The Cacti of the United States and Canada, Benson L, Stanford University Press, 1982

The Cactus Family, Anderson, E, Timber Press, 2001

The New Cactus Lexicon (text volume), Hunt with others, 2006

The Plant List, Website

The Succulent Plant Page, Website

Trees, Shrubs & Cacti of South Texas, Everitt, JH and Drawe, DL, Texas Tech University Press, 1993

Tropicos, Website

…and many other sources



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. 


Opuntia DNA


Opuntia DNA and Ploidy

An index to published chromosome information many cacti and prickly pears is at Index to Plant Chromosome Numbers (IPCN, Tropicos). Another index to many plants is at Chromosome Counts Database, Rice et al., 2016, Website. 

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. 


A Cytological and Morphometric Analysis of a Triploid Apomict, Opuntia ×kelvinensis, Baker and Pinkava, 1987

An Intron Loss in the Chloroplast Gene rpo C1 Supports a Monophyletic Origin for the Subfamily Cactoideae of the Cactaceae, Wallace and Costa, 1996

Opuntia of North America, An Overview, Rebman and Pinkava, 2001

Chromosome Counts of Miscellaneous Cacti, Ferguson, 1991 (unpublished)

Chromosome Counts of Opuntia (Cactaceae), Prickly Pear Cacti, in the Midwestern United States, Ribbens and Majure, 2012

Chromosome Counts, Cytology, and Reproduction in the Cactaceae, Ross, 1981

Plant Cell Nuclei
Plant Cell Nuclei

Chromosome Numbers for the Flora of Organ Pipe Cactus National Monument, Pinkava et al., 1992

Chromosome Numbers, Nuclear DNA Content, and Polyploidy in Consolea, Negron-Ortiz, 2007

Chromosome Numbers in Chihuahuan Desert Cacti, Weedin and Powell, 1978

Chromosome Numbers in Chihuahuan Desert Cacti II, Weedin et al., 1989

Chromosome Numbers in Chihuahuan Desert Cacti III, Powell and Weedin, 2001

Chromosome Numbers in Cacti of Western North America I, Pinkava and McLeod, 1971

Chromosome Numbers in Cacti of Western North America II, Pinkava et al., 1973

Chromosome Numbers in Cacti of Western North America III, Pinkava et al., 1977

Chromosome Numbers in Cacti of Western North America IV, Pinkava and Parfitt, 1982

Chromosome Numbers in Cacti of Western North America V, Pinkava et al., 1985

Chromosome Numbers in Cacti of Western North America VI, with Nomenclatural Changes, Pinkava et al., 1992

Chromosome Numbers in Cacti of Western North America VII, Pinkava et al., 1998

Chromosome Numbers in Cacti of Western North America VIII, Baker et al., 2009

Chromosome Numbers in Miscellaneous North American Vascular Plants, Parfitt et al., 1990

Chromosome Numbers of Some of the Cactaceae, Stockwell, 1935

Club Chollas of the Big Bend, Fenstermacher, 2016

Cylindropuntia chuckwallensis, Baker and Cloud-Hughes, 2014

Cylindropuntia multigeniculata, Baker, 2005

Cytogeography of the Humifusa Clade of Opuntia, Majure et al., 2012

Documented Chromosome Numbers, 2005, trans-Pecos, Weedin and Powell, 2005

Fruit Characters Among Apomicts and Sexual Progeny of a Cross of the Texas Native Opuntia lindheimeri (1250) with a Commercial Fruit Type Opuntia ficus–indica (1281), Felker, et al., 2009

Genome Sizes and Ploidy in Mexican Species of Opuntia, Segura et al., 2007

Grusonia pulchella classification and its impacts on the genus Grusonia, Griffith, 2002

Isolation and Characterization of Polymorphic Microsatellite Markers in Galapagos Prickly Pear Cactus Species, Helsen et al., 2007

Low Levels of Genetic Differentiation between Opuntia echios, Helsen, et al., 2009

Karyotypes, Heterochromatin, and Physical Mapping of 18S-26S rDNA in Cactaceae, Penas, et al., 2009

Karyotpic Studies in (three species) of Opuntia, Palomino and Heras, 2001

Plant Chromosomes
Plant Chromosomes

Karyotypes to Determine Relationships between Species of Opuntia, 2000

Measuring Genome Size of Desert Plants Using Dry Seeds, Sliwinska et al., 2009

miRNA Expression During Prickly Pear Cactus Fruit development, Caballero et al., 2015

Miscellaneous Chromosome Numbers in Opuntieae, Majure et al., 2012

Molecular Based Assessment of Genetic Diversity of xoconostle Accessions, Valadez-Moctezuma et al., 2014

Molecular Based Assessment of Genetic Diversity Within Barbary fig, Zoghlami et al., 2007

Molecular Characteristics of Prickly-pear Cactus (Opuntia) Based on Internal Transcribed Spacer Sequences (ITS) of Queretaro State – Mexico, de Lyra et al., 2012

Molecular Phylogeny and Character Evolution in Terete-stemmed Andean Opuntias, Ritz et et al., 2012

Molecular Studies of Forage Prickly-pear Cactus from Brazil, Catanho Pereira de Lyra, 2015

Molecular Systematics of the Cactaceae, Barcenas, et al., 2011

Multivariate Analysis of Karyotpes in Opuntia, Bandyopadhyay and Sharma, 2000

Natural Pentaploids in the Opuntia lindheimeriphaeacantha Group in Texas, Grant and Grant, 1982

Nomenclatural Changes in Cylindropuntia and Opuntia, Pinkava, 2002

Nuclear DNA in Angiosperms, Bennet and Leitch, 2010

Números Cromosomáticos Para las Cactaceae del Paraguay, Author and date unknown

Opuntia delafuentiana a New Xoconostle from Central Mexico, Martinez-Gonzalez et al., 2015

Plant Cell Walls
Plant Cell Walls

Opuntia diploursina, Stock et al., 2014

Opuntia ficus-indica; Chromosome Races and Origins, Tephrocactus Study Group, Rowley

Origins of Opuntia curvospina, Parfitt, 1980

Phylogenetic Relationships in Opuntia (Cactaceae, Opuntioideae) from South America, Realini, 2014

Phylogeny of Opuntia ss–Clade delineation, geographic origins, and reticulate evolution, Majure et all, 2012

Taxonomy and  Distribution of Opuntia and Related Plants, Puente and Pinkava, date unknown

The Origins of an Important Cactus Crop, Opuntia ficus-indica, Griffith, 2004

Typifications and a Nomeclatural Change in Some Eastern North American Opuntia, Majure, 2014

Using Molecular Data to Elucidate Reticulate Evolution in Opuntia (Cactaceae), Griffith, 2003

What Did the First Cacti Look Like, Griffith, 2004

Opuntia Artist: LCC Krieger

LCC Krieger
LCC Krieger


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. 

Opuntia Artist: Mary Emily Eaton

Mary Emily Eaton
Mary Emily Eaton


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.

How Opuntia Species Are Identified


Opuntia polyacantha, NM
Opuntia polyacantha, New Mexico

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, and original citations and descriptions. 

Bentonii with Fruit
Opuntia bentonii with Fruit, Galveston, TX

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 the identification of plants in the field using published materials. Opuntia Web does Field Botany. 

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 where it was thought there was only one. 

What is a species?

Opuntia sp. aff. valida, AZ
Opuntia aff valida, AZ

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, rigorous morphometric, anatomic, 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 only be 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? 

Opuntia wootonii flower
Opuntia wootonii flower, Belen, NM


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. 


Opuntia hybrids 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 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. 

Opuntia phaeacantha
Opuntia phaeacantha

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 1%genes from Neanderthal humans. An example of introgression in Opuntia might be a pink-flowered population in a species that is generally yellow-flowered.

Checklist of differences between O. lindheimeri and O. engelmannii

Opuntia lindheimeri
Opuntia lindheimeri


Opuntia engelmannii 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.

See O. engelmannii

See O. lindheimeri


Opuntia engelmannii
Opuntia engelmannii
  • 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. 



Opuntia basilaris, NV
Opuntia basilaris, NV

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. 

Editorial Board

Opuntia charlestonensis
Opuntia charlestonensis

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

Mt. Charleston, NV
Mt. Charleston, NV

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

Opuntia ammophila, FL
Opuntia ammophila, FL

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.

Terms of Use

Opuntia camanchica, Carlsbad, NM
Opuntia camanchica, Carlsbad, NM

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