Engelmann, Proceedings of the American Academy of Arts and Sciences 3: 291, 1856
Lectotype; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium (as O. expansa); Herbarium (as O. expansa); Herbarium (as O. expansa); Herbarium (as O. expansa); Holotype (as O. eocarpa); Isotype (as O. eocarpa); Painting (as O. expansa); Photograph (O. expansa, Villa Nueva, NM)
What is Opuntia dulcis?
Opuntia dulcis is a widespread medium-sized prickly pear with sweet fruit–hence the name dulcis.
From Powell and Weedin, 2004, page 169:
Opuntia dulcis is a more upright cactus than O. camanchica, and the spines are fewer and more slender. There are 2-(4) spines per areole in this prickly pear. While spines may be brown at their bases and white at the tips, they vary and may be other colors depending upon the population of this prickly pear. The flowers are yellow with red centers and have slightly more tepals than O. camanchica. Filaments of this Opuntia are pale green to cream or colorless and about 1.5 cm long. Anthers are yellow and about 2 mm long. The style is rosy or white and 2-2.5 cm long. Stigma lobes are typically light green.
When ripe the fruits of O. dulcis are red to purple, obovate to obconic, (4-)5-5.5 cm long, 2.5-3 cm in diameter. The umbilicus of this Opuntia may be shallow or deep. The fruit is smooth with few areoles that have few glochids and few or no spines. The fruit rind is purple; the pulp may be pink, purple, red, or greenish—and juicy. Juice may be colored or clear and is sweet. Seeds are tan, irregularly discoid, 3.5-4.5 mm in diameter. They have a narrow hilar notch and a prominent aril margin 0.7-1 mm wide.
O. dulcis has been described as a variety of O. phaeacantha. However, throughout their overlapping ranges the two cacti are differentiable. O. dulcis is a larger plant with ascending branches, to 2(3) ft. Sometimes the major branches of O. dulcis may be prostrate with side branches rising to 20 to 30 cm. Immature specimens of O. dulcis may overlap in size with O. phaeacantha plants. O. dulcis resembles O. engelmannii in some ways but does not become as erect or large as that Opuntia can. The spines may be in the same arrangement as O. engelmannii, but are more slender. See the original citation. O. dulcis is hexaploid.