Vegetative reproduction by the rooting of detached stem segments (joints) has long been recognized for certain cholla species, but the stem characteristics necessary to employ this reproductive strategy have largely been ignored. In this study, four sympatric cholla species in the northwestern Sonoran Desert, Opuntia acanthocarpa, O. bigelovii, O. echinocarpa, and O. ramosissima, were characterized for their ability to reproduce vegetatively based on the following: (1) the biomechanics and anatomy of terminal joint junctions, which determines how easily a joint will detach from a plant; (2) the rooting ability of detached terminal joints; and (3) field observations of clonal reproduction. When subjected to bending moments, terminal joints of O. bigelovii deflected the least prior to joint junction failure, although its junctions failed under bending moments similar to those for O. echinocarpa and O. ramosissima, whose terminal joints were only 10% as large. The similarity in junction strength among these three species compared to O. acanthocarpa, which was stronger, reflected their similar cross sectional wood areas and essentially similar anatomy of their joint junctions. Detached terminal joints of O. bigelovii also had the greatest rooting ability of the four taxa, followed by O. acanthocarpa, O. echinocarpa, and O. ramosissima. In the field, only O. bigelovii appeared to develop regularly from detached joints. Thus, cholla vegetative reproduction via the rooting of detached joints apparently depends on limited wood accumulation in the joint junctions, which results in biomechanically weak junctions, and an ability to produce adventitious roots, both of which are particularly evident for O. bigelovii.

Key words: anatomy, biomechanics, joint junctions, joint, Opuntia, vegetative reproduction