Opuntia bonaerensis
Speg. Riverina PearErect shrub to 3(–4) m high, occasionally with a small trunk, plants to 5 metres diam. Terminal cladodes compressed, narrowly obovate to obovate or elliptic, 9–32 cm long, 4–14 cm wide, 20–28 (–40) mm thick, glabrous, green and glossy, often tinged reddish purple along the cladode margin and around areoles; areoles 12–32 per cladode face, c. 18–55 mm apart, with reddish-brown glochids; spines absent or 1 (rarely 2) per areole on 1 (rarely several) areoles, erect or variously spreading, 7–48 mm long, 0.7–1.2 mm wide near base, slightly curved towards apex, dark red-brown or reddish-purple with yellowish apex, ageing greyish-brown or pale grey. Flowers (3.5–)6–9.5 cm diam.; sepaloids distinctly crimson tinged; petaloids spreading or somewhat erect, orange, the outer ones reddish-tinged mostly toward the apex; stamens yellow; style pale yellow, stigmas green; hypanthium smooth, dull. Fruit obovoid, shallowly depressed at apex, 6–8 cm long, 2–2.5 cm diam., smooth, spineless, dull, carmine at maturity, deciduous, juicy. Flowers late spring–summer.
MuM, VVP, MSB, RobP, MuF, OtP, Gold, CVU. Also SA, Qld, NSW, ACT. Native to Brazil (Rio Grande do Sul) to NE. Argentina.
Locally common in far north-western Victoria (e.g. roadsides near Ouyen) and along the Murray River near Red Cliffs, noted also in bushland and along rail-lines near Bacchus Marsh, Werribee and Geelong.
At various points in time, the plants in Australia have been referred to as Opuntia paraguayensis, O. cardiosperma, and more recently O. elata. In a non-exhaustive analysis of floristic works, technical documents and digital pages by Aymerich & Font (2023), the authors argue that it has not been possible to assign Australian plants to O. elata s.s. Aymerich & Font (2023) provide a table of comparative character states of related species, illustrations of the character states in Figure 1, as well as colour images. From limited observations (by V. Stajsic) of the plants naturalised in southeastern Australia, herbarium specimens, and a limited review of the images in Australian literature and online sources, the Australian plants appear to be consistent with the character states given for O. bonaerensis Speg. Aymerich & Font (2023) claim that their work shows that O. bonaerensis is the most widespread species from ser. Armatae, perhaps the only one from that series, naturalised in Australia, where it is currently treated as O. elata.