About the genus
All the species of this distinct cactus genus grow naturally in Chile. Most are found near the coast in the Atacama Desert, one of the driest places in South America.
In habitat, the plants receive very little actual rainfall in most years, surviving instead on the frequent mists that drift inland from above the cold ocean. The sea here is unusually cold for the latitude because of the cold Humboldt current which originates in Antarctic waters.
There are about 25 species of Copiapoa, many quite similar in appearance, especially when young. They vary in size from miniatures such as C. laui to huge clusters, up to three metres in diameter, comprising hundreds of stems as with C. dealbata. Almost all have yellow flowers produced from young areoles in the crown of the plant. There are a number with large tuberous roots for storing water to help cope with drought conditions, during which the heads of the smaller-growing species can be flush with the ground and even covered with sand.
How to grow them
Copiapoas are among the most popular of South American cacti. Their natural habitats are a popular destination for cactus tourists because of the wonderful plants which are to be found in spectacular settings, often within sight of the sea, where cacti can often be the dominant vegetation. As well as their attractive appearance, many are famously slow-growing, which means that mature plants are desirable and expensive to buy. The most iconic species is C. cinerea which has a white waxy coating in habitat, a wonderful contrast to its usually black spines. This is a slow-growing plant in cultivation and will only develop its white body in very good light. The small-growing species such as C. laui, C. hypogaea and C. humilis are easy to grow and will often flower when young.
The plants do well in a sunny place in a glasshouse or conservatory The compost should be largely mineral with little organic material. A suitable mix would be half of sterilised loam or John Innes and half of a lime-free fine grit. Good ventilation is important since the plants are prone to scorch, especially early in the year. Some temporary shade at this time of year can also prevent scorch damage.
It is best not to try to rush these plants with fertiliser and lots of water because this can lead to weak spines and atypical columnar growth. Young plants can be watered like other cacti but older plants in larger pots should be treated more gently. Overhead watering with a fine rose can of rainwater on warm summer evenings simulates the mist in nature.
Propagation is usually achieved from seeds. Another easy method is to break up the clumps of stems that are formed by species such as C. laui and C. hypogaea, each head often already having its own root system. Cuttings can also be used but they can have a rather large cut surface and leave a big scar on the parent plant.
Text and photos: Graham Charles
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