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Mike Partridge

In November last year I went on a guided cactus tour to North West Argentina and Chile put together by Willy Smith of Cactus Tours. This was my first visit to see cacti in habitat, my first visit to South America and my first visit to the southern hemisphere. I was particularly drawn to this trip as it promised the chance to see a large number of the ‘small’ Opuntia and allied genera in habitat and because it was in the South American spring the promise that many should be in flower.

This article is an account of a stop at a particularly interesting location during day 4 of the trip when we were en route for the Chilean border crossing at the Paso de San Francisco. The area in question is called Rumi Ryan [also called Rumi Rayan in some descriptions] and lies on National Road 60 in the west of Catamarca province, Argentina, a few miles from the settlement of Chaschuil. The following plants were found growing on the hillside all within a few hundred yards of the road: Puna (now Tephrocactus) bonnieae, Tephrocactus geometricus, Maihueniopsis minuta and Pterocactus kuntzei. We started the day at Fiambalá (this being the last town before the crossing into Chile on this route) and began the slow climb into the mountains. On the road between Fiambalá and Rumi Ryan we stopped at Las Angosturas to see Cumulopuntia boliviana, an unidentified Tunilla species, Soehrensia formosa, Denmoza rhodacantha and Opuntia sulphurea. The latter was a plant we encountered every day in Argentina in many different forms. Although not a small Opuntia by any estimation I found it appealing because of its variation from location to location. The spine length and shape varied from an inch long to five inches or more and from straight to curled. As we climbed higher into the Andes the mountains became more spectacular, the vegetation more limited and the air thinner. When we eventually reached the site in question (Fig. 1) we were at an elevation of approximately 2,900m.

Fig. 1

Fig. 1. Rumi Ryan.

The hillside we explored at Rumi Ryan was a gentle north facing slope littered with rocks of varying size and colour interspaced with fine gravel and sand (in fact not  unlike some of the Martian rover shots I have seen). There was some obvious vegetation in the form of low scrubby bushes and the tough yellow grass which we saw at several locations including at the high point of the crossing into Chile. The nature of the terrain and the small size of the plants sought meant that initially I was unable to find anything resembling a cactus and wandered around peering at the ground until our guide located some specimens. I then realised what it was I should have been looking for - this was a recurring theme for me when searching for small plants in a large landscape.

The first group located consisted of five plants of Puna bonnieae which lay almost flush with the surface of the sand and were coloured to almost exactly match their surroundings (Fig. 2). Once the first group had been found several others were soon located nearby, often partially buried in the sandy gravel and all of a fairly uniform appearance.

Fig. 2

Fig. 2. Puna bonnieae.

They did not much resemble the plants I have seen in cultivation and did not seem to form the multi headed clumps that are normally encountered. They were around ½ to 1 inch in diameter and were rather flattened as can be seen from the photo. The majority of the plants were solitary or had two / three heads maximum and although one or two were showing signs of buds / new growth these were not very far advanced. Unlike the plant I grow under this name these specimens did not have any sign of spination (I understand that the plants most often seen in cultivation come from collections made lower down in the area around Fiambala). I have seen references to a form called ‘nudum’ which may be the same as the plant we saw. I was struck by the obvious similarities in appearance between the P. bonnieae and the form of T. geometricus we saw. Willy has kindly emailed me two additional images of the plants at Rumi Ryan to accompany this article illustrating the plants in flower and fruit (Figs. 3 and 4). 

Fig. 4

Fig. 3. Puna bonnieae in flower (Photo by Willy Smith). 

Fig. 4

Fig. 4. Puna bonnieae in fruit (Photo by Willy Smith).

Close by to these the first plant of the Pterocactus was located (Fig. 5). This was projecting from under the shelter of a stone and had a well developed flower bud. Willy noted that this plant is thought by some to be a type of Pterocactus kuntzei but was not certain of this. I have since consulted Rene Geissler over this and he thought it bore a closer resemblance to Pterocactus megliolii).

Fig. 5

Fig. 5. Pterocactus kuntzei or megliolii.

Close inspection of the area revealed more of these plants almost all growing in the shade a rock which led me to conclude that they needed shelter in order to become established. A little further along the slope several clumps of Maihueniopsis minuta were located. These were growing in close proximity to the larger rocks – either sheltered at the base of them or actually growing in cracks in the rocks themselves. The plants had very small segments between ½” and 1” long and exhibited two very different forms of spination. The majority of the segments in the small clumps had between 2 and 4 short, curved downward pointing spines per areole, whilst the largest and most recent growth on the plants had, in addition, a very long straight downward pointing spine (Fig. 6). The plants bore a strong resemblance to plants I have seen in cultivation under various names including M. minuta and M. mandragora.

Fig. 6

Fig. 6. Maihueniopsis minuta.

After a little more exploration plants of T. geometricus were located (Fig. 7). They were growing in small groups and, in the area I searched, several dozen of them were dotted around between the rock outcrops.  I had been looking forward to seeing these and they did not disappoint. Although they were nowhere more than two segments high they were very pleasing, having neat spination and a ruddy red colouration. I assume that the harsh environment keeps them from growing tall as they can do in cultivation.

Fig. 7

Fig. 7. Tephrocactus geometricus.

The plants were somewhat shrunken from the dry winter season and the size of the craters they sat in indicated that given water they would have been about 25% larger than they now appeared. All the plants I saw bore similar spination being black, curled, downward pointing and held tight to the body of the plant.  Unfortunately none had open flowers but as can be seen from Fig. 7 most plants had more than one bud. There was no trace of any seed pods.

There seemed to be no soil as such at this location the plants growing instead in a mixture of sand and gravel.  The rocks seemed to be mostly granite with a large amount of quartz being evident in the gravel. All in all it was a very interesting location and provided me with the opportunity to see four species, in which I am interested, growing side by side in their native environment.

Additional note by the editor (Alan Hill): The sketch map provides an idea of the route for this section of the tour. It will be noticed that this route is one travelled by several cactophiles. For example the map shows the road between Fiambala and Chaschuil which is where Graham Hole found his “mystery plants” (See TSG 2007 Vol. 13 No. 4, pages 75 and 79-80) and is a route where Graham Charles travelled last year.

Fig. 8

Fig. 8. Map by A. Hill part based on information from Willy Smith via Mike Partridge.
                                                                                                                             
This article was originally published in Tephrocactus Study Group (the 'TSG Journal'), March 2009, Vol. 15, No. 1, pages 4-8 and 11-12. © TSG and Mike Partridge