Of the true Rebutia (as opposed to those which are now included in Aylostera), this is one of the two most northerly, and grows at the highest altitude, growing on the border between Bolivia and Argentina in the high Andes and extending into both countries. It is (so far) only found from a small area of around 80km2. The species was first described by Walter Rausch in 1972 from plants found above Santa Victoria, Salta, Argentina, at an altitude of 3,500m. The plant is named after Walter Rausch’s wife Margaretha.
This dark green to purple-brown skinned, fairly large Rebutia has flowers and fruit that bear similarities to Weingartia (Sulcorebutia), as well as it’s longish areoles which are slightly sunk into the skin. Nevertheless, its body structure and seeds (as well as its genetics of course) mark it as a Rebutia. The flowers are typically large and red with a yellowish or orange throat and yellow stamens, but it also occurs with orange or yellow flowers.
In the wild the plant overlaps with, and is regarded by some as synonymous with Rebutia padcayensis. Plants named as R. padcayensis predominate in the northern part of the range while R. margarethae predominates in the southern part. Mosti and Papini (2011) regard these as two separate species, but the situation is confused in cultivation by growers applying both names to plants indiscriminately. In the greenhouse, the name R. padcayensis is usually given to a greener plant, with uniform coloured, usually smaller flowers, finer spines and a smaller habit. Fickenscher (2021), who also recognises both species, mentions the lighter flower throat colour as being a characteristic of R. margarethae. However, both species (if they are actually separate species) are quite variable in the wild and it may be that the distinction in the greenhouse is an artificial one. As with all of the Rebutia group, our concept of ‘species’ does not fit well with the reality of active evolutionary divergence.
It is a relatively easy plant to grow, and can tolerate short periods of freezing temperatures in winter, as long as it is kept dry during those months. It flowers profusely, usually from the end of April through May in my greenhouse, then sporadically after that until the end of summer. It is not self-fertile, but I have been able to cause seeds to be produced by cross-pollinating plants with a small paintbrush. Seeds are produced in small pods at the base of the dead flowers, which should be left on the plant until late autumn. Picking off the dead-heads and seed pods before they have completely dried can damage the plant allowing disease to get in.
LITERATURE:
Fickenscher, K (2021) Aylostera & Rebutia: Blütenwunder aus den Anden. Deutsche Kakteen-Gesellschaft e.V.
Mosti, S, Bandara, N L & Papini, A (2001) Further Insights and New Combinations in Aylostera (Cactaceae) Based On Molecular And Morphological Data. Pak. J. Bot. 43(6): 2769–2785.
Text and photos by Paul Doyle
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