Opuntia engelmannii (Engelmann prickly pear)

Opuntia engelmannii Salm-Dyck ex Engelm.

Engelmann prickly pear, cactus apple

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Magnoliophyta	Flowering plants, also known as angiosperms
Class	Magnoliopsida	Dicotyledons—plants with two initial seed leaves
Subclass	Caryophyllidae	Cacti, many other succulents, carnivorous plants, and leadworts
Order	Caryophyllales	Includes cacti, carnations, amaranths, ice plants, and many carnivorous plants
Family	Cactaceae	Succulent (water-storing) plants, often spiny
Genus	Opuntia	Prickly pears
Species	engelmannii	After Georg(e) Engelmann (1809-1884), a German-born St. Louis physician and botanist, and prolific author on cacti, North American conifers and oaks

About plant names...

Engelmann’s prickly pear is native to North American deserts, at elevations between 1000-4500' (304-1371 m).

Identification: 3-10' (91-304 cm) high, in clumps up to 15' (4.6 m) wide. Thick pads are oval or rounded. Flowers are yellow to red. Fruit is barrel-shaped, with very short spines or no spines. Spines are chalky white, sometimes yellow. I couldn’t find any significant differences between this species and the variety called Tuna Cactus. See this Opuntia comparison table.

Online References:

Opuntia engelmannii at George and Audrey DeLange's Arizona wildflower site

Opuntia engelmannii on cals.arizona.edu

Opuntia engelmannii on Wikipedia

Opuntia engelmannii at Southeastern Arizona Wildflowers and the Plants of the Sonoran Desert

Opuntia engelmannii on CalPhotos

Opuntia engelmannii at the Lady Bird Johnson Wildflower Center

Opuntia engelmannii on www.saguaro-juniper.com

Opuntia engelmannii on eFloras

References:

Bowers, Nora and Rick; Tekiela, Stan, Cactus of Arizona Field Guide, Adventure Publications Inc., 2008, p. 151