Two species and a distinct evolutionary lineage

The genus includes Maihuenia patagonica and M. poeppigii. In the 2025 classification by de Vos and coauthors, it is the sole genus in the subfamily Maihuenioideae. Its former placement alongside broadly defined Pereskia reflected, among other features, the presence of leaves. Its current separation is based on analyses of relationships across the family. [2-WWW] [de Vos et al. 2025]

The nomenclatural history began with descriptions in Opuntia and Pereskia. Leuenberger compared former names, herbarium specimens and observations of living plants. Numerous names, such as M. tehuelches and M. albolanata, refer to M. patagonica in the current treatment, and M. philippii refers to M. poeppigii. [Leuenberger 2008] [2-WWW]

Leaves, cushions and soft stem axes

Both species spread through strong branching. M. poeppigii forms a compact green cushion in which neighbouring branches and leaves touch. In M. patagonica, the branch arrangement is looser, and older axes may contain extensive dead sections. In the material studied, the lower branches of both species lay on the ground or were partly buried in sand and produced adventitious roots. [Mauseth 1999, p. 308]

The narrow leaves have an approximately circular cross-section. Stomata occur around their circumference, as does photosynthetic tissue. In stems, the epidermis is replaced early by periderm. Small areas of epidermis with stomata remain near the sunken areoles, above parenchyma containing chloroplasts. This anatomy describes the capacity for local gas exchange, without measuring its contribution to the whole-plant balance. [Mauseth 1999, p. 308–313]

Conductive wood and storage tissues

The stems contain abundant parenchyma and mucilage cells. The wood has narrow vessels and tracheids with broad annular or spiral wall thickenings. Between the thickenings are sections more susceptible to deformation. This organisation connects the conductive function with the behaviour of tissues that shrink during drought. [Mauseth 1999]

In older M. patagonica, groups of fibres and bands of bark appear within the wood. M. poeppigii retains a much softer structure. These differences and the different branching patterns describe two structural solutions for a low cushion plant. Details are provided in the two species profiles. [Mauseth 1999]