The taxonomy of the Cactaceae has been in a state of confusion for many years, with both professional and amateur taxonomists endlessly messing around with subfamilies and genera, largely based on subjective assessments. The more recent introduction of DNA analysis has started to put some objectivity into the process.
The current classification of the Cactaceae – the cactus family – divides them into four sub-families. This is based on DNA analysis and a process called phylogenetics which, simply put, looks at the evolution of genera and species and whether they share a common ancestor.
The reason why the genus Maihuenia, with only two species, is in its own sub-family is that it doesn’t have any close relatives. On the other hand the vast majority of cacti – many of which look completely different from one another – are lumped into one huge sub-family, the Cactoideae.
The Cactoideae is divided into a number of what are called Tribes and this is where all the various genera are sorted into more meaningful groups of broadly similar-looking cacti. There are six Tribes in the Cactoideae plus a few straggler genera which haven’t been placed in a Tribe yet. (The Opuntioideae are similarly broken down into Tribes but they look more alike.)
If you would like to learn more, take a look at this article on Wikipedia.
I should mention that in the December 2025 issue of CactusWorld, a summary of a new classification of the Cactaceae is described, a summary of a paper published in Plant Systematics and Evolution (2025) by De Vos et al. I can hear the collective groans from cactophiles around the world. It’s based on molecular relationships (DNA analysis) but for now let’s stick with this one. I’ll revisit this at some point soon.
What makes a succulent a cactus?
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Taxonomy: A rose by any other name . . .
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