The question of natural hybridisation in the genus Copiapoa is one that continuous to intrigue Copiapoaphiles.

• Does the genus consist of a continuum of a single highly variable species with a number of localised population forms resulting from very specific environmental conditions? 

• Would the genus  best be regarded as a small number of distinct species complexes?

• Should a significant number of taxa described over the years be regarded as good species with  hybrids occurring naturally to account for the remaining taxa?

Whichever of these points of view you consider to be most appropriate will affect the question if hybrids occur.

Ritter, in Kakteen in Sudamerika 4:1624, includes a picture of a stem section (abb 1056) of what he believes to be a natural hybrid: Copiapoa krainziana x Copiapoa cinerea.

Discussions continue on whether C. krainziana is merely a form or subspecies of C. cinerea.  What is certain is that the Copiapoa in the Quebrada San Ramon display a tremendous degree of variability.  If any of these are hybrids or merely display the degree of variability within a single species, remains to be seen.

Curt Backeberg (Cactus Lexicon, 1977) observes;

"It would seem that within the relatively restricted area of Chile there must have been quite a small number of ancestral species which, in time, hybridised and gave rise to transitional forms, thus making the delimitation of species a difficult task.

In some cases (e.g. C. krainziana) widely differing forms occur in any sowing from seed, even the spine characters varying widely, while even in the wild those species with more conspicuously grey bodies producing seedlings where the bodies are true green....

....One example of the difficulties of classification is that species which become columnar with age may sometimes have varieties which form clumps....."

In my own collection, I have found on a small number of plants in the Marginata complex, that natural offsets have the mature appearance of the mother plant, but where, when offsets are produced because the top of the main stem has been removed, the offsets have quite a different appearance.  The forced offsets of these clearly ribbed plants produce tubercles rather than ribs and are rather reminiscent of plants in the Humilis complex.  Apical dominance is therefore a subject that requires further study in the genus.

Cultivars

I am not aware of attempts at hybridising Copiapoa in cultivation.  As flower colour and relative size are fairly constant throughout all species, there seems to be little incentive to attempt crosses.

In the UK, plants labelled Copiapoa krainziana x barquitensis were available from the Pete & Ken Nursery in the 1990s. Ken Burke told me that these plants were raised from seed that set on his C. krainziana after it was pollinated with pollen from the only other Copiapoa that was in flower at the time: C. barquitensis.  However, it is well known that many plants will accept their own pollen, even if usually regarded as self-sterile, when the stamen also receives pollen from other plants, even from a different genus or family.  The appearance of the resulting plants is, in this case, within the range of variability that C. krainziana displays in habitat.  I am not aware that any of these plants have now flowered and if further crossing experiments have been carried out with its offspring.

Copiapoa tend to be slow growing and may take a number of years to reach flowering size, discouraging attempts at crossing species when there seems to be no horticultural advantages in doing so.  Copiapoa seedlings are notoriously difficult to identify

Neither am I aware of attempts to cross Copiapoa with species in other genera.

This would be an interesting subject to explore further.