Opuntia cespitosa

Opuntia cespitosa
Opuntia cespitosa

Rafinesque, Bulletin Botanique 2: 216, 1830

Neotype; Herbarium; Herbarium; HerbariumHerbarium (as O. humifusa); Herbarium (with O. nemoralis); Herbarium (as humifusa); Herbarium (as humifusa); Herbarium (as O. humifusa); Herbarium; Herbarium; Herbarium (as O. humifusa); Herbarium

See O. humifusa   See O. lata    See O. mesacantha

Original Description

What is Opuntia cespitosa?

Opuntia cespitosa is a prickly pear in the O. humifusa group of cacti (O. humifusa s.l.). O. cespitosa resembles O. humifusa and has long been overlooked by botanists because it was considered synonymous with that species. O. cespitosa also has similarities with the western species, O. macrorhiza

Details

O. cespitosa cladodes generally appear glaucous-gray. Cladodes have 0-2 spines that are either both erect or both deflexed. Only centrals are produced. O. cespitosa does not have strongly retrorsely-barbed spines, which are common in the related O. mesacantha. The spines of O. cespitosa place it in contrast with O. humifusa, which lacks spines. Typically,  the chains of cladodes are parallel to the ground surface. As with related plants (i.e., O. humifusa s.l.), the cladodes become wrinkled in fall. 

O. cespitosa has yellow flowers with red centers. Filaments are yellow and anthers are pale. The style is white and the stigma is white or pale yellow. The fruit is clavate. 

O. cespitosa is tetraploid.

Other Notes

O. cespitosa is the most common Opuntia species in the eastern states though it has traditionally been subsumed into O. humifusa and was not noticed. It is present in multiple eastern, southern, and midwestern states including AL, AR, CT, GA, IL, IN, MA, MD, MI, MO, MS, NY, OH, VA and WV. It is the only Opuntia that occurs in eastern Canada (far southern Ontario). Recent work by Paul D. Adanick shows that this Opuntia occurs in many locations in TN and KY but that it may not be numerous at any specific location. It is often found in rocky situations but also occurs in dry soils.

Various relevant scientific papers have reported on this Opuntia: Majure, 2014; Majure et al., 2012; Majure and Ervin, 2007. O. cespitosa resembles O. macrorhiza and is related to that taxon. 

Unlike O. cespitosa, other Southeast Opuntia spp. have all-yellow flowers. 

The Flora of the Southern and Mid-Atlantic States (2015) reports:

Vegetatively, it is most similar to Opuntia mesacantha ssp. mesacantha, from which this allopolyploid may be partially derived, although floral features are quite different, and O. cespitosa does not have the strongly retrorsely-barbed spines common in O. mesacantha. This species also can be confused with certain forms of O. macrorhiza, another putative parent of O. cespitosa; both species have yellow inner tepals basally tinged red adaxially.

Opuntia stricta

Opuntia stricta
Opuntia stricta

(Haworth) Haworth, Synopsis Plantarum Succulentarum 191, 1812

Herbarium; Herbarium; HerbariumHerbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium

O. stricta has similarities with O. dillenii, another beach prickly pear

O. stricta is different from O. anahuacensis, but they are both beach prickly pears.

Original Citation

What is Opuntia stricta?

Opuntia stricta is a coastal prickly pear cactus that occurs on the shores of Florida and other southeastern states. The cactus may also occur naturally in the Caribbean, the Gulf coast of Mexico, the eastern shores of Mesoamerica, and on the northern shores of South America.

Details

The Flora of North America online reports: 

O. stricta is a sprawling or erect shrub up to 2 m across and 1 to 1.5 tall. Cladodes are green, flattened, narrowly elliptic or obovate and  10-25(-40) cm long by 7.5-15(-25) cm wide. The edges are generally not strongly scalloped, but may have shallow scallops. Spines are yellow, sometimes aging to brownish yellow. 

Flowers are light yellow and 25 to 30 mm long. Filaments are yellow as are the anthers. The style is yellowish as well. Fruits are purplish inside and out, stipitate, ellipsoid or barrel-shaped, 40-60 by 24-30 mm, juicy, and spineless. Sees are tan, and 4 by 4.5 mm with a 1 mm girdle. 

O. stricta is considered hexaploid, but tetraploid individuals have been reported. Perhaps the differences reflect the existence of two different taxa. 

Other Notes

Britton and Rose reported that this Opuntia is found along the Texas coast, and Weniger (1988) reported that the prickly pear may be found in Galveston Bay. The reports of the plants in Texas may have referred to O. anahuacensis because the authors have not observed O. stricta in Texas. It does occur along the coasts of Alabama, Mississippi, and Georgia and is often confused with O. dillenii. However, the two taxa are distinct and different.

Danny Green reports:

The cladodes on the O. stricta are generally oval or spatulate, whereas those of O. dillenii are obovate and/or rhomboid.

The areoles on O. stricta tend to be flush with the surface of the cladode, whereas the areoles on Opuntia dillenii are elevated above the surface of the cladode. For this reason, the margins of the cladodes on Opuntia dillenii are scalloped or wavy unlike the to be smooth or straight margin of O. stricta.

The leaves of O. stricta are shorter, thicker, and pointed upward (more parallel to surface of the cladode). In contrast, the leaves of the other Opuntia tend to be longer (though not all the time), slimmer, and pointed outwards (more perpendicular to the surface of the cladode).

The spines on O. stricta tend to be straight and perpendicular to the surface of the cladode, and it is common for them to be mottled with brown and yellow. In contrast, the spines on O. dillenii tend to be slightly curved (sometimes very noticeably curved) and usually yellow without mottling. Populations of O. dillenii in the Florida Keys may have mottled spines. John Kunkel Small thought that these Keys prickly pears were a separate and distinct species and referred to it as O. zebrina.

O. stricta tends to be more shrubby in habit or even prostrate-ascending, usually between 2- to 5-ft tall. Exceptional specimens of O. dillenii may be 10-ft tall and have a very discernible trunk. However, it is more common to see shorter O. dillenii plants that are 3- to 6-ft tall. Irrespective of height, O.  dillenii is seldom prostrate-ascending.

Finally, cotyledon morphology separates the two Opuntia species. The cotyledons on O. stricta are heart shaped, half as long as those of O. dillenii, and pointed outward, whereas the cotyledons of O. dillenii are oval,  elongate, and pointed upwards.

Although it is an easy plant to grow where temperatures do not drop below 20F, O. stricta is a sprawling plant and may give a garden an untidy look. It is a cheerful bloomer. 

Opuntia polyacantha

Opuntia polyacantha erinaceae
Opuntia polyacantha erinaceae

Haworth, Supplementum Plantarum Succulentarum 82, 1819

Original Description

What is Opuntia polyacantha?

Opuntia polyacantha is a variable prickly pear cactus ranging from Mexico near California, to Texas, to the Rocky Mountain states and the Great Plains, and north into Alberta and Saskatchewan. This prickly pear cactus has even been observed in dry areas in Minnesota and Missouri. This Opuntia is more much more widely spread than the ubiquitous O. phaeacantha

Details

Opuntia polyacantha
Opuntia polyacantha

We recognize 7 varieties of this prickly pear cactus. Not all have been formally described as varieties (e.g., O. polyacantha rhodantha is cited as a stand-alone species), but they represent our concept of the species. Nonetheless, the taxonomy of this Opuntia is complicated, and there are many expressions of O. polyacantha. Some do not fit precisely into the 7 varieties described here. It is possible that new taxa will be recognized within the currently broad concept of the taxon. Alternately, some varieties may some day be condensed with others. Fruits are dry at maturity; flowers are often yellow but may be orange, pink, or magenta. Seeds are large. Read the original description. O. polyacantha is tetraploid, but perhaps one or more other ploidies are represented in this large and diverse group of prickly pears.

O. polyacantha is tetraploid. 

Varieties

Other species have been treated as varieties of O. polyacantha including O. nicholii and O. trichophora (see Powell and Weedin). But these are treated as separate species herein because they are hexaploid or diploid, respectively and because they are don’t intergreade with the varieties described here. 


O. polyacantha erinacea (Engelmann & J.M. Bigelow) B.D. Parfitt, Cactus and Succulent Journal (Los Angeles) 70(4): 188. 1998

Herbarium; HerbariumHerbarium; Herbarium; Herbarium; Herbarium

Opuntia polyacantha erinacea has areoles that are usually large and relatively close together. The cladodes are typically very thick and often elongate. The plants tend to form upright clumps. They have many spines, usually mostly slender and terete. The spines can be stiff or hair-like, even on the same plant (some eastern populations of this prickly pear cactus have mostly plants with very thick stiff relatively short spines). The spines of this prickly pear cactus vary in color but are often light. The fruit is usually more elongate than in var polyacantha and often reddish when initially ripe (but soon fading to brown or tan as they dry).  O.  polyacantha erinacea is found in rocky areas (occasionally sandy areas) in the Mojave Desert and on hot rocky south slopes in the Great Basin Desert north almost to (or perhaps into) Idaho.  It grows in hotter areas of canyons up the Colorado and San Juan Rivers into southern Utah and almost to the Four Corners in Arizona (it was mostly behind dam building and populations were destroy by reservoirs).  This Opuntia variety grows in southeastern California, Nevada, northern Arizona, Utah, and Colorado. Plants at high elevations in the Mojave Desert and southern California sometimes spread more than typical plants and sometimes are nearly spineless, whereas some plants at lower elevations may have enough spines to visually obscure the stem. Some botanists consider O. polyacantha var erinacea to be a separate cactus species, but we treat it as a variety of O. polyacantha herein, especially because it intergrades with, and readily interbreeds with, the other varieties. 

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O. polyacantha hystricina (Engelmann & J.M. Bigelow) B.D. Parfitt, Cactus and Succulent Journal (Los Angeles) 70(4): 188. 1998

Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium

Opuntia polyacantha hystricina is very much like var erinacea, but the joints of this Opuntia are usually not so thick, and the plants are broader, lower, and more openly spreading in habit (as is the case for most O. polyacantha varieties).  This prickly pear cactus is found in areas with at least a modicum of summer rainfall in cold winter deserts and in grasslands from eastern Nevada and southwestern Utah to southwestern Colorado, central New Mexico, and across most of northern Arizona.

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O. polyacantha juniperina (Britton & Rose) L.D. Benson, Cacti of Arizona (ed. 3) 20. 1969

Herbarium; HerbariumHerbarium; Herbarium; Herbarium; Herbarium; Herbarium

Opuntia polyacantha juniperina is much like var polyacantha in many traits, but it has much fewer spines that are confined to the upper areoles or which may be nearly completely absent. The lower areoles of this Opuntia may have only one or two tiny spines or no spines. The fruit is often spineless or nearly so. This prickly pear cactus is found in mountainous areas of the Colorado Plateaus and Southern Rocky Mountains, but it is rare in the Front Range region. It is found in southern Wyoming, Colorado, eastern Utah, northern Arizona, and northern and central New Mexico. Similar groups of plants are scattered into Idaho and north into northern Wyoming and in the Black Hills as well as the higher plateaus and mountain country of northern Arizona. It is replaced to the west by var utahensis (the division is the north-south trending, central high plateaus and mountains of Utah). It usually grows in open conifer woodland, mountain scrub, or in areas of sagebrush.

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O. polyacantha polyacantha Haworth

Lectotype; Herbarium; Herbarium; Herbarium; Herbarium; HerbariumPainting

Opuntia polyacantha polyacantha forms a low spreading prickly pear cactus and usually has roundish pads (shape varies somewhat). The areoles are small and close together in this Opuntia. The spines are numerous with one stout, terete central spine that is is often 2 to 2.5 cm long (occasionally another one or two centrals may be present that are likely to be flattened). Several (to many) smaller spines radiate around the central central. Spine color is highly varied and has been the basis for several of synonymous names. Fruit of this prickly pear cactus tends to be roundish with short stout spines. It grows mostly in grasslands but occasionally into scrub and woodlands in mountains. It is found on the Great Plains and in the Rockies, from Alberta, Saskatchewan and Minnesota southward to central New Mexico, and the panhandles of Texas and Oklahoma. This Opuntia has been reported IA and MO. It also occurs in southern Idaho and eastern Utah. Similar plants grow in the Columbia Basin between the Blue Mountains and southern British Columbia that seem to represent this variety too; these may be westward continuations of populations in Idaho and Montana.

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O. polyacantha rhodantha K. Schumann, La Semaine Horticole 1897 (as O. rhodantha)

Neotype; Herbarium; Herbarium; Herbarium; Herbarium

Opuntia polyacantha rhodantha has not been formally described as a variety of the O. polyacantha prickly pear cactus, but we treat it as one herein. It has areoles that are large and relatively far apart. Stem segments are usually very thick and may be elongate; they are generally “lumpy” because the areoles are prominent. Generally, cladodes are dark- or dull-waxy green. The spines of this Opuntia variety are stout, varied in color, and have annulate markings.  The fruit has prominent (sometimes elevated) areoles that are relatively far apart, usually with stout short spines (but sometimes nearly spineless). This Opuntia is found mostly in desert in northern halves of Colorado Plateaus and Great Basin, lapping into Southern Rockies, Snake River Plains and Wyoming Basin. It also grows in Utah, western Colorado, southwestern Wyoming, southern Idaho, southeastern Oregon, and parts of eastern Nevada.

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Opuntia polyacantha schweriniana, Handbuch der Kakteenkunde. Einleitung und Beschreibung der Pereskioideae und Opuntioideae. 1: 607. 1958 (K. Schum.) Backeberg

HerbariumHerbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium

Opuntia polyacantha schweriniana tends to be a miniature replica of vars polyacantha, juniperina, or hystricina–spination in this prickly pear cactus varies. It grows at high elevations (often above the other varieties) in the Southern Rocky Mountains in eastern Utah, Colorado, northern New Mexico, southern Wyoming, with pockets of similar plants further north in Wyoming and in the Black Hills.  Also a few patches at high elevations occur in the San Juan drainage in northeastern Arizona. See the original description (as O. schweriniana). 

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O. polyacantha utahensis Purpus (O. utahensis), Monatsschrift für Kakteenkunde 19: 133. 1909

Neotype; Herbarium; Herbarium; Herbarium 

Opuntia polyacantha utahensis has areoles that are relatively far apart. The cladodes are most often thickish and elongate, sometimes a bit lumpy (usually not), and light in color. The cladodes may be yellowish green and the spines are usually pale white to yellowish in color. The spines are slender.  The areoles of this prickly pear cactus are relatively far apart on fruit and sometimes spineless.  It is found mostly in lower mountains in woodland or scrub, but sometimes it occurs in sagebrush areas. It grows in eastern California (rare), Nevada, western Utah, and perhaps into southern Idaho and southeastern Oregon.

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O. polyacantha “other varieties” (Engelmann & J.M. Bigelow) B.D. Parfitt

Opuntia polyacantha is a widespread species found from Canada and the northern Midwest to California and down the backside the Sierra Nevada mountains into Mexico. Some plants don’t fit into the varieties we describe and are worthy of more study. This prickly pear cactus is the most widespread Opuntia in the United states. 

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O. polyacantha garden plants

There are many naturally occurring O. polyacantha plants with especially beautiful flowers. Also, many garden plants have been created by hybridization. Many vendors sell Opuntia hybrids, including Rainbow Farms. There are Facebook pages devoted to hybrids such as Flower Mountain. Or you may write to Derrill Pope at mokee007@aol.com.

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Opuntia Web

Opuntia engelmannii fruit
Opuntia engelmannii fruit

Introduction

Updated August 08, 2019

Opuntias are the prickly pear cacti. There are over 90 species of Opuntia in the United States. We describe them here.  

Opuntias are unique cacti with unusual shapes and beautiful flowers.  They are part of the opuntiad supergroup of cacti. 

The “big three” states for opuntias are Texas, New Mexico, and Arizona. However, the East has a number of species too. Most states have at least one native prickly pear. The good news is that many western opuntias will grow in a variety of climates. So, you can grow them in your garden. 

Cholla Web is our sister Website, and it describes other opuntiads of the USA (chollas and dog chollas).

The Details

Of the many prickly pear cacti in the United States, some have been forgotten by time, and many names have fallen by the wayside. Some species have multiple names. Some species look superficially alike, and only close inspection can tell them apart (e.g., O. humifusa and O. mesacantha).

Thus, casual observation might indicate one Opuntia type where there are actually two or three. 

What We Do

Opuntia valida
Opuntia valida, Artesia, NM

We describe Opuntia species, and we provide multiple photographs so you can see details. We take photos in habitat so that you can see how the plants look and grow in different seasons. 

We use historical records and current findings along with our own field studies to identify prickly pears, their differences, and their similarities. 

Our goal is to describe a prickly pear cactus in easy-to-understand terms so that you can find all of them in habitat.

A group of editors verifies all the information in this Website, and we strive for accuracy. But we are always happy to learn new things. Just write to us or leave a comment. If you have an Opuntia, maybe we can help you identify it. 

We generally do not described Opuntia hybrids though there are many beautiful plants in gardens. Though prickly pear hybrids occur in Nature, they are not the norm. We concentrate on species. 

The Garden

This Website is not about gardening, but we agree that many Opuntia species are excellent garden plants. Here are lists of the ones we like. 

What are 10 best small Opuntias for gardens? 

These prickly pear cacti are small, easy to grow, cold hardy, and floriferous: excellent for any garden. They have the added benefit of growing in flower pots, and they are easily obtained too. 

What are 10 best large Opuntias for gardens? 

Large, majestic prickly pear cacti are popular in gardens too. Though they require more room, they are worth it because they are amazing statement plants in, or out, of flower. Large plants are found in many southwestern gardens, but you can grow some in the Midwest or the Southeast. They are all good bloomers and one produces sweet fruit. 

Through prickly pears are mostly desert plants, there are prickly pear species that will grow in the Southeast, the Northeast, and the upper Midwest

Many opuntias grow naturally in climates without strong freezes, but some come from northern areas or high altitudes can fly through winters of exceptional cold. We like to grow opuntias, and writing about them helps us and others understand the various species and decide what to grow and photograph.

Conclusion

Opuntia alta
Opuntia alta, TX

Opuntia species are part of the supergroup: opuntiads. They are the plants with flat stems also known as paddle cacti.

Their names are confusing and many species are difficult to tell apart. Some species have been forgotten and we try to match up the species we see with the descriptions written 100 (or more) years ago. 

This Website has descriptions of over 90 prickly pear species and over 1500 photographs of them. 

Prickly pear cacti are unique and worth studying because: 

  • They are so numerous in the warmer parts of the county,
  • They are easy plants in gardens,
  • They provide fun detective stories about identification.
  • There are lost or forgotten species to pair with the original descriptions,
  • They are uniquely drought resistant and heat tolerant,
  • They have beautiful flowers and edible fruits, 
  • They are important plants for desert wildlife, 
  • There is much yet to be learned about their basic biology. 

Opuntia macrorhiza

Opuntia macrorhiza
Opuntia macrorhiza

Engelmann, Boston Journal of Natural History 6: 206, 1850

Holotype; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; HerbariumHerbariumHerbarium; Herbarium; Herbarium; Herbarium; HerbariumHerbarium; Herbarium (O. macrorhiza-like); Herbarium; Herbarium HerbariumHerbariumPrint (Britton and Rose, v1 1919, plate XXVIII); Print (Addisonia, 1916, plate 19); Print

See O. cespitosa, a similar eastern plant

O. pottsii can be mistaken for O. macrorhiza.

Original Description

What is Opuntia macrorhiza?

Opuntia macrorhiza is a small, prostrate prickly pear cactus, seldom reaching 40 cm in height though it may sprawl 1 m across. O. macrorhiza has a large geographic range, being found from New Mexico and Utah into Texas and north to Colorado as well as the the Plains States and the Midwest. O. macrorhiza does not occur in Arizona but has been reported for that state. Apparently reports of O. macrorhiza in Arizona are due to O. pottsii, a species that can be mistaken for O. macrorhiza.  

Details

From Powell and Weedin

O. macrorhiza is a low, sprawling plant less than 30-40 cm high. Plants often have tuber-like swollen roots to 2.5 cm thick. Cladodes are wrinkled after the first winter, 7.5-13 cm long and 8-12 cm wide, oval, ellipsoid, or obovate. Often there are 1-3 main spines from areoles in the upper portions of pads. The lowest spine may be deflexed, whereas the other two project outward or upward. Spines are pale, often tan-white. Glochids are usually obvious and may be profuse. 

Flowers are yellow with sharply defined orange or red centers. Stigmas are cream-colored or pale green as is the style. Flowers vary in size but may be 6 cm long and 5-8 cm in diameter. Filaments are cream-colored distally and greenish basally. Anthers are yellow. The pericarpel is slender and about 3 cm long. Fruits are variable throughout its large range and may be greenish, orange, or red with a sour taste. Some fruits are obovoid and 2-3 cm long and 1.5-2 cm in diameter with few and small areoles. Other fruits are clavate. Spines are rare on fruits. Seeds are irregularly shaped, 3-3.5 mm in diameter, 1.5-2 mm thick, notched at the hilum, and with a narrow margin to 0.5 mm. 

O. macrorhiza is tetraploid. 

Other Notes

O. macrorhiza is a variable and widespread cactus. In fact several forms have been named including: O. greenei, O. stenochila, O. macroflora, and perhaps more. All of these possible variants are included in our concept of O. macrorhiza here. They may actually represent discrete taxa or only minor variations. More study is needed. O. macrorhiza has always stirred controversy about its correct identification. New information suggests that the the broad concept of  O. macrorhiza presented here could be be reconsidered.

Reports of O. macrorhiza in the Midwest and East may be due to O. cespitosa, a similar-appearing taxon. 

Opuntia macrorhiza is a superb garden plant because it is tough, cold hardy, easy to grow, and not too large. The yellow flowers can be striking with their red centers. Additionally, many garden forms exist with pinkish and reddish flowers. 

Opuntia humifusa

Opuntia humifusa
Opuntia humifusa

(Rafinesque) Rafinesque, Flora Medica (or Manual of the Medical Botany of the United States of North America) 2: 247, 1830

Neotype; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; HerbariumHerbarium (as O. calcicola); Herbarium (as Cactus humifusus); Herbarium (as Cactus opuntiaDrawing (Curtis’s Botanical Magazine, vol. 50: pl 2393, 1823 [as Cactus opuntia]); Drawing (Audubon, Birds of America [double elephant folio edition, plate 94, as Cactus opuntia] ca. 1830) 

See O. cespitosa  See O. lata  See O. mesacantha

Original Citation

What is Opuntia humifusa?

Opuntia humifusa is a distinct species though it has been lumped with other taxa. This prickly pear ranges from the mid-Atlantic states to Virginia. Specifically it is found in Kentucky, West Virginia, Virginia, North Carolina, Maryland, Pennsylvania and New Jersey; there is also an outlying population in Mississippi. Perhaps it occurs in adjacent states but any reported plants are assumed to be O. cespitosa or O. mesacantha.

Details

O. humifusa is difficult to differentiate in the field from O. cespitosa, O. mesacantha, and O. lata. However, O. humifusa does not have spines, whereas the others often do. 

From The Flora of North America Online

Shrubs: forming clumps or often prostrate, usually only 1 or 2 stem segments tall, to 0.2 m  Stem segments: not disarticulating, dark or bright shiny green, wrinkling when stressed, circular to broadly oblong to obovate, 5-17.5 × 4-12 cm, fleshy, usually tuberculate, glabrous; areoles 4-6 per diagonal row across midstem segment, oval to circular, 2-4 mm diam., not raised, sometimes somewhat sunken; wool tan to brown. Spines:  absent. Glochids: in dense crescent of adaxial edge of areole and in dense tuft overtopping crescent in age. Flowers: inner tepals pale to bright yellow throughout, 20-30 mm diam.; filaments yellow to orange; anthers pale yellow to cream; style and stigma lobes white. Fruits: greenish, tardily becoming apricot to brownish red, elongate, 30-50 × 12-20 mm, fleshy, tapering at base; pulp green and sour. Seeds: tan, 3.5-4.5 mm diam., thickish; girdle protruding to 1 mm.

Thus, O. humifusa is spineless, and flowers are yellow without red. 

O. humifusa is tetraploid. 

Other Notes

O. humifusa s.l. is a constellation of similar-appearing taxa–a collection of species that originated through hybridization. O. humifusa was unlumped from closely related prickly pears by Dr. Majure who showed that the one species (O. humifusa) was in fact a complex of at least four related taxa (O. humifusa, O. cespitosa, O. lata, and O.  mesacantha). There are multiple recent publications by Dr. Majure that are relevation (Cytogeography, Mississippi, Ecology, Taxonomic Revision, and Evolution) that provide new information about these related Opuntia species. All of these plants appear to be related to O. macrorhiza, but the precise nature of the relationship(s) is not known. 

O. humifusa is not a desert plant. Rather, it is often an opportunistic cactus in areas that receive heavy rainfall or runoff part of the year but which are hot and dry other parts of the year. Hence, it is often found growing on rocky outcrops. In drought and hard cold the plant shrivels considerably, sometimes collapsing completely until clement conditions return. 

O. humifusa is a long-time garden favorite. It is easy to grow, tolerant of rain and snow, the right size for most gardens, and a cheerful bloomer. 

Opuntia gilvescens

Opuntia gilvescens
Opuntia gilvescens

Griffiths, Annual Report of the Missouri Botanical Garden 20: 87, 1909

Holotype (as O. gilvescens); Herbarium; Herbarium; HerbariumHerbarium; Herbarium; Herbarium; HerbariumHerbariumHerbariumHerbariumHerbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium. Except where indicated, all specimens  were originally interpreted as O. phaeacantha

O. gilvescens is related to O. camanchica

O. gilvescens is related to O. phaeacantha

Original Description

What is Opuntia gilvescens?

Opuntia gilvescens is a widespread, medium-sized cactus. It occurs from Oklahoma all the way to and southern Nevada and desert California. It is a common plant in Arizona. It is often confused with O. phaeacantha, in part because there is no slot for it in most guidebooks. 

Details

O. gilvescens has nearly round or obovate cladodes that are generally dull. Main branches rest upon the ground and other branches rise to 30-80 cm. O. gilvescens is often a symmetrical plant. Mature plants may be 1 m across. Cladodes  may be 20 × 25 cm, but they are often smaller. Spines are not numerous, and there may only be 2 major spines; but there may be 1-4 on first-year growth. The tips of spines are translucent. 

Many O. gilvescens flowers have a blush of red at the bases of the interior tepals, but some individuals may have rust-colored veining that can darken or spread as the flower ages. Cacti with all-yellow flowers may be found. Also, some cacti have pink flowers as in parts of southern Utah. Stigmas are green, pale green, or yellow-green. Anthers are yellow or cream-colored. Filaments are yellow but can darken towards the base. Fruit is round-bottomed or barrel shaped, but may occasionally have a narrow base, ripening to pink, reddish, or even greenish-pink. Flesh is greenish or pink-green, sometimes dark. Seeds are about 0.75 cm across with a 1 mm rim.

O. gilvescens is hexaploid.

Other Notes

The authors have found this prickly pear in Oklahoma (Arbuckle Mountains and west), in western  and central Texas, in many parts of New Mexico as well as in Arizona, southern portions of  Nevada, Utah, and Colorado, and in the mountains of the eastern California Mojave Desert. Similar-appearing prickly pears have been found in the mountains east of Palm Springs, California. Additionally the plant occurs in the Chihuahuan Desert of Mexico. 

Plants from southwest New Mexico and adjacent Arizona are often pale; sometimes they have rhombic or more elongate joints and pale spines. Plants from the Mojave Desert area often have round pads with fewer than average areoles and a few pale spines. Plants from the Chihuahuan Desert of Mexico and into central Texas are often dark in appearance; they may become strongly red-purple in winter and the spines can be black.

In central New Mexico, O. gilvescens fits the type description well. Some southern populations, such as populations on the east side of the Sandia Mountains and down into Socorro County, and again in the Alamogordo area, often have wide, curved pads creating an interesting potato chip look.

Opuntia fragilis

Opuntia fragilis
Opuntia fragilis

(Nutt.) Haworth, Synopsis plantarum succulentarum 82, 1819

Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Painting

Original Citation

What is Opuntia fragilis?

Opuntia fragilis is smallest opuntia and one of the most cold hardy. It is found throughout in parts of the West and the northern Midwest. Frequently O. debreczyi is frequently misinterpreted as O. fragilis or a hybrid of O. fragilis in the Mountain West and the Great Basin. 

Details

Dr. Eric Ribbens writes:

Opuntia fragilis (Nutt.) Haw. is a small, cold-hardy prickly pear. It has pads 1 to 3 cm long and longer than wide, and spines can be longer than the pad, or short.

This Opuntia forms a sprawling prostrate mat up to 30 cm in diameter; rarely are there erect chains of more than 2 or 3 pads. The cladodes of this Opuntia are remarkable because they are ‘fragile’. They separate easily–sometimes with just a touch.

Flowers are large and yellow, with creamy greenish to reddish centers. Older plants often develop a thick rootstock at the base of the plant. Large plants can be comprised of hundreds of pads on numerous flat chains. The pads are often rather rounded instead of flat, and that it does not ever set fruit in the Midwest.”

O. fragilis is hexaploid. 

Other Notes

Britton and Rose reported that O. fragilis is seldom in flower and even less often in fruit.

O. debreczyi is a western opuntia that is about twice the size of O. fragilis. It is frequently misinterpreted as O. fragilis and thus distorts knowledge of the actual distribution of the species. The two species are known to occur together. 

Many garden hybrids are known. They are excellent garden or pot plants because of their small size and ability to withstand many conditions. Some are brightly colored and all are cold-hardy. 

For more information about the taxonomy, appearance, geographic distribution, and ecology of O. fragilis see the following publications by Dr. Eric Ribbens.

Permission to reproduce some materials for this page through the courtesy of  the Cactus and Succulent Society of America and Dr. Ribbens. The journal articles are copyrighted and may not be reproduced elsewhere.

Opuntia orbiculata

Opuntia orbiculata
Opuntia orbiculata

Salm-Dyck ex Pfeiffer, Enumeratio diagnostica cactearum hucusque cognitarum 156, 1837

Herbarium (as O. crinifera); Herbarium (seedling);  HerbariumHerbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Note: unless indicated otherwise, all herbarium specimens were submitted  as O. engelmannii; Herbarium (O. dillei); Herbarium; (O. dillei); Painting; Painting

Original Description

What is Opuntia orbiculata?

Opuntia orbiculata is a large prickly pear cactus that is found over much of the West. It may be semi-upright or may sprawl along the ground. It may be nearly spineless or have multiple spines. O. dillei is a spineless variant. 

Details

Opuntia orbiculata is a prickly pear cactus that may reach 1 m tall, but exceptional plants may be 1 1/2 m or 2 m tall. Small plants in cold areas may be 0.5 m tall or less. Unlike O. engelmannii it is often noticeably wider than tall for a large plant. The cladodes on this prickly pear are thick and may be 12-inches wide, or they may be smaller. Cladodes are often nearly circular (orbicular), but they may be spatulate, oval, obovate, or even obdeltoid. Often, pads on this prickly pear cactus have a bluish look to them, but this is not determinative. In clement growing conditions, the plants make close-branching shrubs. In drier locations the plants may be short and spreading; they may even have trailing prostrate branches. Spines on this Opuntia are variable, but are typically white or yellow, and they may have dark bases. They can be lightly curved or straight.

Flowers are yellow with green stigmas. Fruit is egg shaped, barrel shaped, or even subglobose. Fruit is umbilicate, reddish purple, and perhaps 5 cm by 6 cm. There is little or no suggestion of a narrowing at the base of fruits. Seeds are flattened, slightly angular, 3-4 mm in diameter. Seeds have a conspicuous marginal callus about 0.5 mm with a narrowly rounded margin. 

Ploidy is unknown. 

Other Notes

Like so many large opuntias, O. orbiculata is often misidentified as O. engelmannii because there is no slot for this cactus in guidebooks. O. orbiculata occurs in Oklahoma, Texas, New Mexico, Arizona, the desert mountains of Nevada and California, and northern Mexico. See a table comparing O. engelmannii with O. orbiculata

Details may be lacking, but evidence supports the name, Opuntia orbiculata, for plants on this page. First, the name (O. orbiculata) is valid, but it has a confused history. Material seen by Britton and Rose was assumed by them (and I have no reason to doubt they were correct) to be the same material that was named by Salm-Dyck. It was supposedly from South America, but Britton and Rose realized that this was in error and that it had to be from North America, likely northern Mexico. Nothing similar occurs in South America.

Based on the bits of information the authors have collected as well as the description of Britton and Rose, the plants shown on this Web page are correctly identified. There really aren’t any other candidates that fit. See the discussion and description by Britton and Rose, 1919. 

However, this uncertainty about the name suggests tentative use for now. If this name should be thrown out, the name, O. dillei (Griffiths, Annual Rep. Missouri Bot. Gard. 20: 82-83, 1909), was given to nearly spineless plants of the same taxon, and there is no ambiguity about that name (except for Benson’s incorrect belief that it was a hybrid).

As is typical of most Opuntia species, the plants are variable, and while many pads on many plants are nearly orbicular (circular), this is not a totally diagnostic trait. Oval, obdeltoid, obovate, and even spatulate pads are common. As with many Opuntia spp, rare pads may even have pointed ends. Pads are thick or thick appearing and fleshy seeming, more so than is the case in O. engelmannii or O. lindheimeri

 

Opuntia engelmannii

Opuntia engelmannii
Opuntia engelmannii

Salm-Dyck ex Engelmann, Boston Journal of Natural History 6(2): 207, 1850

Lectotype; Isotype (as O. gregoriana); Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium (as O. gregoriana); Herbarium (as O. gregoriana)

See O. lindheimeri

See checklist of differences between O. lindheimeri and O. engelmannii

Original Description

What is Opuntia engelmannii?

Opuntia engelmannii (including O. gregoriana) is a large western prickly pear. It has been confused with other large cactus species such as O. valida, O. discata, or O. orbiculata

Details

From Powell and Weedin: 

O. engelmannii has variable pads that are generally obovate, broadly elliptic, or orbicular. Pads may be 20-30 cm long and 15-25 cm in diameter. Under optimal conditions the pads of this Opuntia grow thick and heavy. The cladodes of O. engelmannii are pale-green and tend to stay that color year round unlike many opuntias that may have pink or purple pads in the winter. Spines are carried in the bird’s foot pattern and are chalky white, brown, tan, or even dull yellow–they darken considerably at the base. Some spines curve, but some may be perpendicular to the cladode surface. There may be as few as 1-2 spines or as many as 6 spines per areole. Radials may be present in mid-stem and upper stem areoles, 0.35-1 cm long, acicular.  

There is much spine variation in O. engelmannii, but one pattern is common. The thick spines are distributed over most areoles except the lowest. There are at least 3 spines splayed in a “bird’s foot” pattern. However, areoles with 2 or 4 (or even 5) spines are not uncommon, and weakly spined individuals also occur. The glochids of this Opuntia (and O. lindheimeri) are distributed in a distinctive pattern. They either circle the areole or are spread throughout the areole and are not generally arranged in a tuft. This is especially true of mid-stem areoles. The glochids are not densely crowded and are of unequal lengths, 3-5(9) mm.

The flowers of O. engelmannii are clear yellow without red centers. Orange venation may be observed on inner tepals on close examination. The yellow color in this Opuntia is not as brilliant as in O. lindheimeri. The large flowers are 7-8 cm in length and diameter. The filaments are cream-colored to pale green and 1-2 cm long. The style is cream-colored and the stigma lobes are green. The pericarpel is typically about 5.5 cm long and 3.2 cm in diameter. Scattered circular areoles with tan hairs and bristle-like glochids project from all parts of the pericarpel areoles.

Fruits of this Opuntia are deep purple, reddish–purple, or dark beet-red, and older fruits can be very dark. The barrel-shaped fruits are 5.5-8 cm long and 3.5-5 cm in diameter. Alternately the fruits may be of the same size but oval or obovate instead of barrel shaped. The fruits do not have an obvious narrowing or neck. The fruit pulp is dark red, very juicy, and very sweet. The generally spineless fruits of this Opuntia may have slender spines 5 mm long in some upper areoles. The seeds are small (2)3-4 mm in diameter and numerous, and they have a narrow hilar notch and a narrow beakless aril margin.

O. engelmannii is hexaploid.

Other Notes

O. engelmannii is the the tallest wild prickly pear from the Rio Grande River to California. This Opuntia is usually upright with upright branches, but some plants spread out wider than tall. It can can be 1-2(2.5) m wide and 1.5-2.5 m tall, but young plants are smaller. Plants in northerly locations or at high altitudes are smaller. The pads are typically egg-shaped, obovate, oval, or sometimes circular. Cladodes are green or or sometimes barely blue-green, but are seldom dark green. Pads may even be yellow-green when stressed.

Less-spiny-than-usual O. engelmannii plants in southeast New Mexico and near El Paso, Texas have been called O. gregoriana, but that taxon is considered synonymous with O. engelmannii herein. O. engelmannii ranges wide and far and there may be types that could be considered varieties. But varieties have not been formally described.

O. lindheimeri was validly described as a variety of O. engelmannii, but we accept it as a separate species herein. Though they are related, the two taxa are different. See the checklist of differences between O. engelmannii and O. lindheimeri.