Article Index by Title

Tony Roberts

The genus Puna was created by Roberto Kiesling [1] in 1982 to encompass just two plants which in much earlier times had been known as Opuntia subterranea (1905) and Opuntia clavarioides (1837). At the time Kiesling’s intent was quite valid for these plants had similar morphological characteristics such as their habit and tap roots. In 1997 a new plant was discovered and described [2], making a total of three in the genus; this was of course Puna bonnieae. However, subsequent studies (both of the seed structures [3, 4] and recent definitive DNA studies [5, 6]) have shown that these three plants now fit better within three different genera of the Opuntioideae. Historically, it is quite amazing that these small plants have undergone so many names changes over the years; two of them have resided in five different genera (see table 1).

Table 1

C. subterranea     M. clavarioides     T. bonnieae
         
1905 - Opuntia        
1936 - Tephrocactus   1837 - Opuntia    
1980 - Cumulopuntia   1930 - Cylindropuntia     
1982 - Puna   1941 - Austrocylindropuntia   1997 - Puna
1999 - Maihueniopsis   1982 - Puna   1999 - Maihueniopsis
2011 - Cumulopuntia   1999 - Maihueniopsis   2001 - Tephrocactus

 

But never mind the names; let’s have a closer look at these three species for they are truly gems of the small Opuntiads.

Cumulopuntia subterranea

This plant occurs in the Argentinean province of Jujuy and in the Potosi department of Bolivia. Like all the plants discussed in this article it usually consists of a single or just a few heads and has a significant tap root – its species name subterranea clearly indicating that most of the action takes place underground! The small bodies have numerous areoles with very short glochids and spines. In cultivation, whether grafted or not, it can make a fine clump given time, and has flowers about 3cm across which can be white to pale-pink or occasionally somewhat darker (fig. 1).

Fig. 1

Fig. 1. Cumulopuntia subterranea (photo: Les Hewitt)

In 2000, a subspecies was discovered near Incahuasi in the department of Chuquisaca in Bolivia, and originally described as Tephrocactus pulcherrimus [7], but now classified as C. subterranea subsp. pulcherrima [5]. This plant tends to proliferate more than the type species both in habitat and culture (albeit slowly) and has a larger (4-6cm) red or sometimes violet flower. My specimen came from a plant found by Martin Lowry in 1997 originally assigned simply as “Opuntia subterranea”, but when it flowers you can see the distinction (fig. 2).

Fig. 2

Fig. 2. Cumulopuntia subterranea subsp. pulcherrima BLMT069.02

Maihueniopsis clavarioides

Maihueniopsis clavarioides is the eldest statesman of these three species although it didn’t receive this name until 1999 [8]. It also originates from Argentina, and has been seen in collections for many years. Often plants were grafted, and they proliferated more quickly, resulting in prize winning specimens like the one owned by David and Kathleen Briggs from Bridlington (fig. 3). You can see from this the abundance of strange-shaped segments (club-like and fingers) that can occur. Offsets from such plants will root down quite readily, but they don’t seem to do much on top for quite a while as they are busy developing a tap root below ground, to take on more closely the habit of plants found in the wild.

Fig. 3

Fig. 3. Maihueniopsis clavarioides (David & Kathleen Briggs’s National Show winner)

Tephrocactus bonnieae

The third of these choice Opuntiads is Tephrocactus bonnieae, which held the name Puna for the shortest time of all. In their original article [2] Ferguson and Kiesling mention that the plant was first taken for a Tephrocactus seedling and, somewhat ironically, just four years later Stuppy confirmed it to be indeed a Tephrocactus based on a detailed examination of its seeds [3]. In cultivation Tephrocactus bonnieae is often seen as a grafted plant (typically, grafted on Austrocylindropuntia subulata) resulting in a multi-headed specimen (fig. 4). New segments start off quite brown in body colour gradually turning green and then becoming even paler after they have matured. Such grafted plants show a greater propensity to flower and for me sometimes have two flushes of flowers, in spring and then in late summer – the flowers are spectacular, pinkish white to pale-pink and about 5cm across (fig. 5). Individual segments will root down, again slowly and, like with some other Tephrocactus species e.g. T. molinensis, it helps if you almost bury the segment – just be careful it doesn’t rot!

Fig. 4

Fig. 4. Tephrocactus bonnieae, a grafted plant

Fig. 5

Fig. 5. Tephrocactus bonnieae in flower

In its natural habitat near Loro Huasi in the Argentinean province of Catamarca, these plants occur as tiny specimens that you are unlikely to find unless you know where to look or they are in flower, for they are almost completely underground. There is also a totally spineless form occurring at a nearby locality (fig. 6). Again, I just have a grafted plant of this form; it has not yet flowered for me, but you can clearly see the young and more mature segments (fig. 7).

Fig. 6

Fig. 6. Tephrocactus bonnieae, the spineless form in habitat (photo: Mike Partridge)

Fig. 7

Fig. 7. Tephrocactus bonnieae, the spineless form grafted

So the ultimate Cactus Trivial Pursuit® question! Is there another genus containing just three species which have subsequently been transferred to different genera? Or is this unique?

In conclusion, these are all plants you should have in your collection, if you haven’t already, for they won’t take up much space. But perhaps, now is the time to take the plunge, to re-label your existing plants, and say “Puna no more!”

References:
1.    R. Kiesling, Hickenia, 1982, 1, 293
2.    D. J. Ferguson and R. Kiesling, Cact. Succ. J. Am., 1997, 69, 287
3.    W. Stuppy, Kew Bulletin, 2001, 56, 1003
4.    W. Stuppy, in Studies in the Opuntioideae (Succulent Plant Research , Volume 6, ed. D. Hunt and N. Taylor), 2002, 25
5.    D. Hunt, Cactaceae Systematics Intitiatives No. 25, October 2011
6.    C. M. Ritz et al, Molecular Phylogenetics and Evolution, 2012, 65, 668-81(ePublished on 2nd August 2012)
7.    J. J. Halda and L. Horácek, An. Mus. Richnov. Sect. Natur, 2000, 7, 75
8.    E. F. Anderson, Cact. Succ. J. Am., 1999, 71, 324

This article was originally published in Tephrocactus Study Group (the 'TSG Journal'), December 2012, Vol. 18, No. 4, pages 48-57. © TSG and Tony Roberts. It is reproduced here with the permission of the author.

Postscript (June 2013)

I said in the original article that the spineless form of T. bonnieae had never flowered for me - well, in June 2013, it duly obliged! What a surprise it was, for the flower was a markedly different colour (fig. 8) compared with the more normal form. An even greater surprise was that just 24 hours later the colour of the same flower had changed considerably (fig. 9).

Fig. 8

Fig. 8. Tephrocactus bonnieae, the spineless form in flower

Fig. 9

Fig. 9. Tephrocactus bonnieae, the same flower 24 hours later