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   Cactus are indigenous to the Western Hemisphere and are found in their greatest concentration along the Tropics of Cancer and Capricorn.  They are found in deserts, on seashores, in mountains, and on plains, balds, and glades.  Cactus are native to every American state except Vermont and Maine and they are as evocative of the western United States as Sagebrush. 

     Cactus come in a number of shapes from flat to cylindrical to circular; they are minute and gigantic; their flowers are commonly very large and attractive; their fruits are edible (some delicious, some not so); and they have evolved a number of structures and processes that make them perfectly at home in what we humans call "a hostile environment": They have a tough, waxy outer layer that reduces moisture loss; they produce chlorophyll not in leaves but in the outer cells of the stems; they convert absorbed water into a mucilaginous liquid that can be stored in large quantities in tissues capable of expanding; and many Cactus root easily into new plants from the broken pads or stems of older plants.

    "Cactus" is Greek for "prickly plant"; the word was used by Linnaeus in the 18th century to describe a prickly, thistle-like Asteraceae found in Italy.  "Cactus" was then used in the 19th century for the newly discovered spiny, drought resistant plants of the Western Hemisphere.

     This page (and several others) contains photographs of the Cactus genus, Opuntia.  Since flower color in both Opuntia phaeacantha and Opuntia polyacantha ranges from shades of yellow to copper-yellow to pink to magenta, flower color cannot be used to distinguish between the two species.  The spines and glochids of the fruit, seed texture, spine shape, and spine spacing are key distinguishing characteristics. 

     The Cactus genus Opuntia is highly variable, hybridizes, and therefore plants of the same species have many different characteristics.  Unfortunately, various botanists do not agree on which characteristics belong to which species.  For example, William Weber indicates that Opuntia erinacea and Opuntia polyacantha both exist in western Colorado and that the former is distinguished from the latter by its flattened spines.  But then Weber goes on to say, that it "is often impossible" to distinguish between the two species because they hybridize.     

     Stanley Welsh, author of the excellent A Utah Flora, questions whether O. erinacea and O. polyacantha are distinct species, but "following tradition" he retains both species in his Flora.

    Both the Synthesis of the North American Flora and the Flora of North America agree that there is only one species, Opuntia polyacantha and the other is a variety, O. polyacantha variety erinacea.  But they add a special new dimension to the confusion: they indicate that this variety is almost exclusively found in southern California and Nevada. The variety does not exist in Colorado and is found in only one county in the far southwest corner of Utah. Quoting FNA: "The name Opuntia erinacea has been widely misapplied to some plants of other varieties of O. polyacantha".  

    Further, whereas Weber and Welsh indicate that the characteristic that separates O. polyacantha from O. erinacea is the round spines of the former and the flattened spines of the latter, this distinguishing characteristic is not even mentioned by FNA in the description of either of the two Opuntias.

    FNA and the Synthesis indicate that the three varieties that are found in the Four Corners area are O. polyacantha variety polyacantha, O. polyacantha variety hystricina, and O. polyacantha variety nicholii.

    The 2012 final volume of the 8 volume Intermountain Flora indicates that O. polyacantha has varieties nicholii, hystricina, polyacantha, and erinacea with variety polyacantha being the most widely spread variety through the West and variety erinacea occurring only in Nevada, southern California, and far western Arizona.

Amen.

    Lower pads of a number of Cacti (including Opuntia phaeacantha and Opuntia polyacantha) often sprawl on the ground, soil accumulates on the uphill side of the pads, and they are often buried. New pads grow on the higher soil level.

    The name "Opuntia" was used by Theophrastus for a plant, not in the Cactus Family, which grew near the Greek town of Opus. Somehow "Opuntia" was centuries later applied to this genus of Cacti. 

Click for more Opuntia photographs.

 
Opuntia phaeacantha
Opuntia phaeacantha (Prickly Pear Cactus)
Cactaceae (Cactus Family)

Semi-desert, foothills. Openings. Spring, summer.
Canyons of the Ancients National Monument, May 24, 2004.

There are a number of varieties of Opuntia phaeacantha, and all commonly grow three to five feet tall and wide, but in the Four Corners area they are most commonly ground hugging and sprawling.  Opuntia phaeacantha has pads that range from three to ten inches in diameter, one-to-three inch brown-tipped spines that are widely spaced, and, most often, yellow flower tepals with red-to-orange tinting at the base. It is not unusual, though, to find pink and salmon flowers.

It is common to find Opuntia phaeacantha pads that have semi-circular chunks missing from them -- the work of deer. The smaller nibbles are taken by squirrels, chipmunks, and mice; the missing fruit has often been eaten by critters or has disappeared into collecting bags of humans who relish it for jams, pies, and muffins. 

"Phaeacantha" is Greek for "dusky thorn" referring to the brown-tipped spines.

 

Opuntia phaeacantha

Opuntia phaeacantha

Opuntia phaeacantha

Opuntia phaeacantha

Opuntia phaeacantha (Prickly Pear Cactus)
Cactaceae (Cactus Family)

Semi-desert, foothills. Openings. Spring, summer.
Canyons of the Ancients National Monument, May 24, 2004 and Butler Wash, Utah, May 21, 2014.

Click for more Opuntia phaeacantha photographs.

Opuntia polyacantha

Opuntia polyacantha

Opuntia polyacantha (Prickly Pear Cactus) 
Cactaceae (Cactus Family)

Semi-desert, foothills. Openings. Spring, summer.
Canyons of the Ancients National Monument, March 20, 2014 and Hidden Valley Trail, Utah, May 10, 2007.

In the Four Corners area Opuntia polyacantha plants are low and sprawling with pads two to six inches wide and long.  Spines grow close together with many arising from the same point. ("Polyacantha" is Greek for "many thorns".)  Flowers, ranging from yellow to hot pink (see below), are very large in relation to the pad size. New pads are soft, as are their short, undeveloped spines.

The winter of 2006-2007 produced ideal growing conditions for many plants, including the Cacti shown in the photograph at bottom left, and you can see how much larger the new, soft green growth is.  Pads of some varieties and hybrids are elongated, as pictured here, but most are nearly circular.  The ideal 2006-2007 conditions favored bud and flower growth as well as pad growth.  There are nine buds ready to open. 

Opuntia polyacantha hybridizes readily and the Flora of North America now lists a number of varieties, three in our Four Corners area.

Click for more O. polyacantha.

Opuntia polyacantha

Opuntia polyacantha

Opuntia polyacantha (Prickly Pear Cactus) 
Cactaceae (Cactus Family)

Semi-desert, foothills. Openings. Spring, summer.
Hidden Valley Trail, Utah, May 10, 2007 and Canyons of the Ancients National Monument, May 17, 2009.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Opuntia phaeacantha

Range map for Opuntia polyacantha  

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