Opuntia mesacantha

Opuntia mesacantha
Opuntia mesacantha

Rafinesque, Bulletin Botanique 1: 216, 1830

(Also Opuntia mesacantha Raf ssp mesacantha Majure)

See O. cespitosa    See O. humifusa    See O. lata

Neotype; Herbarium; Herbarium; Herbarium; Hebarium (as O. humifusa); Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium


What is Opuntia mesacantha?

Opuntia mesacantha is a southeastern prickly pear found in Georgia, Alabama, and Florida and adjacent areas in the southern Piedmant and Gulf Coast Barrier Islands. It is absent in the Florida peninsula. It resembles O. humifusa and O. cespitosa but has distinct differences; see Majure, 2014 and Majure et al, 2012


O. mesacantha is a prostrate plant that may branch in all directions to 1 m across. Cladodes may be spined or unspined and are smooth in outline, obovate or rotund, occasionally elliptical. Spines are stout (0.95-1.3 mm in diameter). 

Flowers are pure yellow with no red. Fruits are reddish at maturity. Seeds are 5.0-5.9 mm long. 

O. mesacantha and O. lata are difficult to differentiate in the field, but Adanick et al., 2019 developed a method to measure stomates in the field and differentiate the two taxa easily.  See the original descriptionO. mesacantha is tetraploid, whereas the related O. lata is a diploid. Like other eastern prickly pears, O. mesacantha colonizes sandy or rocky areas that become dry between rains. 

Concerning the differences between O. mesacantha and O. humifusa, The Flora of the Southern and Mid-Atlantic States (2015) reports:

O. humifusa is an allotetraploid (2n=44), cryptic species that is most easily confused with O. mesacantha ssp. mesacantha, from which it can be separated by its lack of spines…and generally increased number of areoles per diagonal row across the cladode face at midstem (4-5 vs. 3-4 in O. mesacantha), generally inserted glochids (vs. exerted in O. mesacantha), and smaller seeds (4.0-4.6 mm long in O. humifusa vs. 5.0-5.9 mm long in O. mesacantha) with a smooth funicular envelop (instead of the upraised funicular envelope in O. mesacantha ssp. mesacantha).

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

What is Opuntia cespitosa?

Opuntia cespitosa is a prickly pear included 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 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. 

Unlike O. humifusa, 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 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, TX, 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. See the original description. O. cespitosa is tetraploid.

Various relevant scientific papers have reported on this Opuntia: Majure, 2014; Majure et al., 2012; Majure and Ervin, 2007

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 tunoidea

Opuntia tunoidea
Opuntia tunoidea

Gibbes, Proceedings of the Elliott Society of Natural History 1: 272, 1859

O. bentonii is similar to O. tunoidea

Herbarium; Herbarium; Herbarium

What is Opuntia tunoidea?

Opuntia tunoidea is a prickly pear cactus that occurs along the coast of South Carolina. It has been confused over the years with O. dillenii (see Britton and Rose). 


Opuntia tunoidea is erect or semi-erect to approximately .5 or 1 m tall, and the plants have large, ovate to obovate cladodes. The yellow spines may 1-1.5 cm long and are tipped with brown.

Flower details are not known. 

Gibbes reported the prickly pear suffered from cochineal scale (Dactylopius sp.), and we found plants infested with Cactoblastis cactorum. Interestingly this Opuntia has a general similarity to O. bentonii of the Gulf Coast, but there are differences. More studies are needed including comparisons of fruits, flowers, and overall morphology, etc. If the two taxa are the same, the correct name for O. bentonii would be O. tunoidea, the name with precedence. Read the original description.

O. tunoidea is unusual because it is a largish cactus that occurs in a northerly location on the Eastern Seaboard. It appears to occur infrequently though it is sometimes grown in local gardens. 

Opuntia lata

Opuntia lata
Opuntia lata

Small, Journal of the New York Botanical Garden 20: 26, 1919

(Also Opuntia mesacantha Raf ssp. lata [Small] Majure)

Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium (as O. impedita); Herbarium (as O. impedita); Painting

See O. cespitosa    See O. humifusa    See O. mesacantha

What is Opuntia lata?

Opuntia lata is prickly pear cactus known from central Georgia to northern Florida and east to central Mississippi where it occurs in grassy areas and other openings in pinelands. It is similar to O. mesacantha


O. lata forms a prostrate prickly pear that may branch in all directions forming irregular mats up to 1 m across. Although prostrate, the last cladode on a branch may tend upwards. Cladodes are elliptical or sometimes narrowly obovate or obovate, up to 4-15 cm long, and deep green. They are often lightly scalloped in outline. Spines may be in the margins only where there are 1-2 per areole. Spines are delicate (0.7-0.9 mm in diameter). 

Flowers are yellow, 7-9 cm wide, and there are many petals. The stigma is white. The fruit is clavate and many seeded 5-6.5 mm long. Seeds are about 5 mm in diameter. 

The type specimen was collected near Gainesville, FL. A taxonomic position as a subspecies of O. mescacantha was was proposed (Opuntia mesacantha Raf ssp. lata [Small] Majure). See the original description. O. lata is diploid. 

O. lata is similar to O. mesacantha upon visual examination. However, the latter is tetraploid. Adanick et al., 2018 (in press) developed a method to measure stomates (size and distance from each other) in the field to differentiate the two taxa. 


Opuntia pusilla (O. drummondii)

Opuntia pusilla
Opuntia pusilla

(Haworth) Haworth, Synopsis Plantarum Succulentarum 195, 1812

Neotype; Neotype; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium;  Herbarium; Herbarium; Herbarium (O. frustulenta); Painting

What is Opuntia pusilla?

Opuntia pusilla is a small prickly pear cactus of the coastal plains from North Carolina, across northern Florida, to Mississippi. While thought of as a beach cactus, this small prickly pear cactus occurs more than 150 miles inland.


The stems of this prickly pear cactus are purplish-red under stress, flattened, elliptic to linear, sometimes subcylindric (to subspheric), 2.5-5(-8) × 1.2-2.5 cm. The stem segments are fragile and detach easily. Spines (0)1-2(-4) per areole are restricted the the distal half of the areoles, but some areoles may have no spines. Spines are porrect to spreading, terete and 20(30) mm.

The flowers of this Opuntia are completely yellow. Fruits become red-purple and are barrel shaped. Seeds are tan, subcircular, flattened, and 4 to 6 mm in diameter with a slight girdle. 

O. drummondii may be the correct name for this Opuntia (L Majure, page 167). Some reports (Weniger, 1988) place it on the northern Gulf Coast of Texas also, but the authors have not observed it there. Several other specific epithets have been applied to this smallest of the southeastern opuntias including tracyi, and pes-corvi. Perhaps these are synonyms or perhaps they are discrete taxa yet to be sorted out. See the Cytogeography of the humifusa clade of Opuntia

O. pusilla has been reported to be diploid, triploid, and tetraploid. These ploidies indicate that there are different, but similar-appearing taxa, or they may may only represent ploidy differences within a single taxon. All are treated as a single taxon herein. See the original description.

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

What is Opuntia humifusa?

Opuntia humifusa is a distinct species though it has been lumped with other taxa. This prickly pear ranges from New England to Virginia (Georgia?).


O. humifusa is difficult to differentiate in the field from 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.

NoteO. humifusa is spineless.  Flowers are yellow with no red.


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 four related taxa (O. humifusaO. cespitosa, O. lata, and O.  mesacantha). There are several relevant publications by Dr. Majure (Cytogeography, Mississippi, Ecology, Taxonomic Revision, and Evolution) that provide new information about these related Opuntia species.

Ecology, etc

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. 

Read the original citation. Opuntia humifusa is tetraploid, but diploid populations are reported.  

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.