Opuntias are the pricklly pear cacti. The plant is composed of flat pads. Glochids are present at the aeroles. Large spines are usually, but not always present. Classification at the species level is often difficult. The opuntias hybridize creating intergradations between species. For example, in the west foothills of the Sandia Mountains at 6,200 foot elevation Opuntia engelmanii, Opuntia polycantha, and Opuntia erinacea are common. Clear examples of each species abound. Examples of species with characteristics intermediate between erinacea and polycantha are also observed. Similiar descriptions are noted in many references.

To differentiate between species the most important characteristic is location. Where is this prickly pear observed? Next most important is the overall plant size and height. After considering the above the characteristics below are considered.

efloras

 

santa-rita

Purple Pricklypear

efloras

spinosibacea

efloras

tortispina

Plains Pricklypear

efloras

  
  southern Arizona, just West of NM border to near Tucson. only big bend area of texas. high plains species, west texas, panhandle, E NM plains, E Colorado, W Kansas, Neb.  
Habit shrubs or small trees erect to 2 m. shrubs to small trees to 1.5 m. low, 0.4 m, creeping from clumps.  
Pad Size 10-20x9.5-20 cm, mean 10 cm. x 10 cm. 10-25 x 7.5 x 11 cm, mean 16 cm. x 9 cm. 6.5-15x4-10 cm. , mean 10 cm x6.5 cm.  
Aeroles 6-8 per midstem row. 4-5 per diagonal row. 6-8 per diagonal row.  

large Spines

 0-2 per aerole, few at pad edges. 1-5 per aerole. 1-3 per aerole. sometimes twisted. none
Pad Surface green, violet when stressed. green, purple near aeroles. grey, wrinkled with stress.  

Spine length

 to 40 mm. to 70 mm. 25- 70 mm. mean 42 mm.  
Glochids cresent at adaxial edge, almost incircling aeroles, subapical tuft. cresent at adaxial edge, along aerole edge, subapical tuft. good adaxial tuft  

flower Color

Size

yellow

25-45 mm.

yellow, red basal

35 mm.

yellow to gold, red near base.

30-40 mm.

 

Filaments

Anther

pale yellow

yellow

yellow

pale yellow

pale yellow

yellow

  

Stigma

Style

light green

white

yellow green

green

green

pale greenish

  

Fruit

Spines

purplish, green inside, fleshy,

spineless.

yellow to red, fleshy

first fleshy, then dry.

white spines, 25 mm.

purple red, fleshy, 30 x22 cm.

spineless.

  
Location arc in south arizona E of Tucson, W on NM line. limestone hills, slopes, 2,700 feet. high plains grasslands, PJ woodlands, 4,400 to 5,600 feet.  

Seeds

 

 4 mm., convex. tan 4.5 mm. whitish to tan 4 mm.  
Varieties none none none.  

hybrids

 

 with Opuntia chlorotica between aureispina and phaecantha apparently halfway between macrorhiza and polycantha.