The five varieties of Opuntia echios are quite variable in form, a phenomenon thought to result from adaptation to differing conditions on different islands (2) (3) (5) (6). The smallest, such as O. e. zacana, are shrubby and low-growing, never reaching more than a metre or two in height (2) (5) (7), while others, such as O. e. gigantea, grow into tall trees and are among the largest Opuntia species in the Galapagos (2) (3) (8). Opuntia echios usually has a well-developed trunk, which is spiny when young and later develops reddish, flaky bark (2) (3) (5). The more shrubby forms generally have softer spines, and tend to grow on islands where there are fewer browsing herbivores and lower competition with other plant species (3) (6) (9).
Opuntia echios produces flat, fleshy pads, up to 45 centimetres long and 32 centimetres wide, covered in evenly spaced groups of 2 to 20 or more yellowish to brown spines. The spines, up to 12 centimetres in length, tend to be erect, stiff and sharp on young plants, and more bristly, almost hairlike, on mature individuals (2) (5). The pads of Opuntia echios produce large yellow flowers, up to ten centimetres across, which develop into the greenish “prickly pear” fruits which give the Opuntia cacti their common name. These roundish to oblong fruits may be over seven centimetres in length, and are covered in spines and short, barbed hairs, known as glochids (2) (3) (5) (9).
- Height: up to 12 m (2) (3)
- Trunk diameter: up to 1.25 m (2) (3)