Erect shrub 2–5 m high, to 4 diam., basal stem segments thickened and trunk-like to 1 m high and 40 cm diam. Stem segments firmly attached, obovate to broadly obovate to suborbicular, (10–) 18–35 cm long, 14–30 cm wide, 10–20 mm thick, compressed, not tuberculate, dull green to grey green, glabrous. Areoles 50–100 per stem segment face, 18–40 mm apart, circular or subcircular, 3–4 mm wide, not raised, with wool pale creamish, ageing grey. Leaves succulent, terete, conical, 4–6 mm long, caducous. Spines 2–8 per areole, at most areoles, variously spreading or some appressed or most retrorse, 20–40 (–70) mm long, 0.7–1.2 mm wide at base, ± terete, straight, usually stout, not barbed, pale yellow to dark grey. Glochids few, inconspicuous, 0.5–0.8 mm long. Flowers (30–) 50–80 mm diam.; outer tepals reddish, succulent; inner tepals yellow to orange, spreading, broad-obovate, 25–40 mm long, 18–23 mm wide, the apex obtuse and entire; staminal filaments pink, anthers pale yellow; style very pale yellow, stigma lobes green; pericarpel (at anthesis) tuberculate, spineless or spiny. Fruit solitary, barrel-shaped to subglobose, (40–) 50–80 mm long, 18–50 mm diam., tuberculate, umbilicus deep, often with spines near apex, pink to red at maturity, succulent and juicy. Seeds 3–4 mm long, pale brown.
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A cactus. It is shrubby or treelike. It grows to 2-4 m tall. The main stem is 80 cm tall and 30-40 cm wide. The pads are spiny and round. They can be 30 cm across. The flowers are yellow or orange. They are 6-7 cm long. The fruit are round and yellow to red. They are edible.
In Queensland Opuntia streptacantha is an environmental weed in open woodland and shrubland habitats. Near Ghinghinda Homestead it grows in Eucalyptus crebra, Casuarina pauper, and Eremophila mitchellii association. At Theodore State Forest it is a weed in Acacia harpophylla, Eucalyptus melanophloia and Corymbia citriodora woodland, where very common. It also invades dry scrub, and hillsides. In Victoria it has been collected from near Merbein (far NW part of the State), where growing in mallee in a dune area, on calcareous red soil.