One of the small, choice opuntias is Maihueniopsis minuta and this plant should be high on your ‘wants list’.
It was first found in Argentina by Backeberg (1936) and, like many of the small opuntias at the time, was named as a tephrocactus; hence it was described as Tephrocactus minutus. Subsequently it was renamed as simply Opuntia minuta by Castellani (1950) before being given its current accepted name Maihueniopsis minuta by Kiesling (1984).
This species benefits from well-drained compost (eg one part John Innes to one part coarse grit) and can be watered from mid-March to end-September (UK climate), keeping it on a high shelf in your greenhouse. However if you water it as early as March you are unlikely to see many flowers later in the summer for it will grow new segments instead. If you withhold water for as long as possible, until late May or even until you see the first sign of buds, you will be more successful with its flowering.
Fig. 1 Maihueniopsis minuta Rauh 65245
The first two pictures are of the same plant (labelled Rauh 65245), a clone which was sent by Kiesling to Rauh in 1984, collected from the Sierra de Pie de Palo in San Juan Province, Argentina. Each segment is tiny, less than 1cm long (the plant is in an 8cm pot) and yet the plant has flowers which are 4–5cm wide – how such flowers suddenly appear from such small segments is quite remarkable!
Fig. 2 Maihueniopsis minuta ‘mandragora’
Another clone of M. minuta which has larger, more elongated segments (and previously was given the species name mandragora) is seen in the third and fourth pictures. The first of these shows a plant which has been well watered as the new segments are quite turgid. There were no flowers that year but the following year, when water was withheld, the story was quite different, for it had just one new segment but five flowers.
Tony Roberts
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