Opuntia cespitosa

Growth form and stem segments

Opuntia cespitosa forms shrubs reaching about 30 cm tall. Segments are arranged in chains, often with their broad surface parallel to the ground. They are obovate, nearly circular or elliptic. The revision description gives lengths of 3,8–18,7 cm and widths of 3,2–11,3 cm. Young segments have a pronounced glaucous coating and develop transverse wrinkles in winter. [Majure et al. 2017]

The glochids are dark red, carmine or amber, later turning brown. Long spines, when present, usually occur singly or in pairs in an areole and are 1,5–4,3 cm long. Their number, orientation and presence also vary within a plant. Roots may be fibrous or tuberous, a variation linked to substrate in the revision. [Majure et al. 2017]

Flower and seed

The inner tepals have red, carmine, orange-red or pink-red bases. Stamen filaments are yellow, reddish at the base, while the stigma is white to cream, with 6–10 lobes. The colour of the flower centre, together with segment and glochid characters, is one useful distinction from typical O. humifusa. [Majure et al. 2017]

The dark red or orange-red fruits reach 2,7–4,5 cm long. Seeds were described as longer than in O. humifusa, measuring 4,9–5,4 mm, with a broader, somewhat uneven band of the funicular covering. Within the described range, flowering occurs from early May to early July. [Majure et al. 2017]

Distribution and sites

POWO gives a range from southeastern Canada to the eastern and east-central USA. The revision indicates that most sites lie west of the Appalachians, with populations extending into Ontario. Habitats include prairies, open patches of vegetation with junipers, and limestone and sandstone outcrops. [2-WWW] [Majure et al. 2017]

Origin and historical data

The species is a tetraploid with a chromosome number of 2n = 44, interpreted as the product of crosses between lineages of the O. macrorhiza complex and southeastern opuntias of the O. humifusa complex. In the central United States, the revision authors identified populations with features suggesting possible introgression, or secondary gene flow between taxa. [Majure et al. 2017] [Majure et al. 2012a]

Older records identified as O. humifusa or O. compressa may include this species. This also applies to accounts of cultivation and overwintering. Frost tolerance assessment should retain the identification and provenance used in a given experiment. Creating a separate taxon profile does not change the identification of historical material. [Majure et al. 2017]