Copiapoa humilis subsp. tocopillana (Ritter) D. Hunt, Cact. Syst. Init. 13: 14 (2002)
Basionym: C. tocopillana Ritter, Kakteen in Südamerika 3: 1072 (1980).

This taxon was discovered by Ritter back in the early 1960s, although it was not formally described by him until 1980. This is the most northerly variant of the species, indeed the most northerly of the whole genus and one of the least known in habitat and in cultivation. It grows in the extremely dry region north of Antofagasta in the vicinity of Tocopilla, where it is found on the tops of the coastal hills at 800m to 1,000m. Only at such altitudes do the mist and clouds supply sufficient moisture to allow the plants to exist. Ritter documents several locations ranging from the abandoned town of Cobija northwards to Tocopilla

Figure 4 Copiapoa humilis subsp. tocopillana PH433.02 (Planta Michilla 900m)
adult and juvenile plants in rock cracks

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and beyond. I suspect it is widespread in the area but exploration is difficult due to the steep terrain and it requires a very dedicated cactus enthusiast to climb 1,000 metres up a barren hill in search of plants! I first saw this plant close to the town of Tocopilla in February 2001. The plants were few and far between, on rocky hill tops, looking incredibly dehydrated as no rain had fallen since 1997. The body was highly contracted, with a dense covering of spines, making it difficult  to determine whether they were alive or dead, and equally difficult to determine the genus to which they belonged! A few smaller plants were found in rock cracks, protected from most of the intense sun. These looked much more like juvenile heads of C. humilis subsp. humilis and confirmed the relationship to this taxon. There was little other vegetation in the area, although cacti are well represented with scattered specimens of Eulychnia iquiquensis, Neoporteria residua and the recently described Eriosyce (Rimacactus) laui.

Figure 5 The habitat of Copiapoa humilis subsp. tocopillana
(Tocopilla 900m) on very barren coastal hills

However, when I returned to the area in November 2002 the habitat looked very different. Earlier that year some rain had fallen and the specimens of C. humilis subsp. tocopillana were plumped up into short  columnar plants with signs of fresh  growth. This time the distinct tuberculate and dark coloured body so typical of C. humilis was clearly visible.

Many annual plants had appeared and were in full flower. C. humilis subsp. tocopillana is very rare in cultivation and much of the material in circulation purporting to be this taxon is misidentified. This taxon differs from the type in having a solitary body, taller than broad, 10-15cm high by 5cm across, bluish green especially on young growth, to grey green and burnt brown on old growth. It is quite hard to the touch, with 10-15 indistinct ribs. The roots are large and tuberous, connected to the body by a thin neck. The spines are black, weathering to grey and then eventually light brown. Central and radial spines are straight and needle-like, slightly longer than the type, about 10 radials of length 10-25mm, and 1 to 4 centrals, slightly stronger to 15-30mm in length. Flowers are smaller than the type being 20mm across and 25mm long, yellow with a dark midstripe on outside of petals.

Figure 7 Copiapoa humilis subsp. tocopillana PH436.04
(Tocopilla 900m) showing signs of fresh growth in November
2002, after EL Niño rains