Some plants like what you do for them and others do not. Some are happy in about any soil mix you put them in and others rebel. For years I have been going in circles with Micropuntia pygmaea. I have had several kinds of soil and once in a while even had the plants in flower. With the introduction of acidic water the plants came alive. Over the years the plants have not enjoyed the several different soil mixes I have planted them in. They may perk up for a few months and then they seem to go into decline. There are several factors to consider in growing these plants. One, is its growing area, two, is how the plant grows, and three, the rain fall season.
The growing area is quite wild desert. All the plants I found have been on low sloping hills. The elevation is from about 4,500 feet to over 6,000 feet. In places it grows where sheep have graze. Benson seemed to think that the plant has been changed and that M. pygmaea, is a mutant form of a plant, caused by sheep grazing on the plants for less than a hundred years. There are areas where sheep have never grazed and the plants are there, unchanged from the plants where the sheep have grazed. I have seen many plants that sheep or cattle have grazed on and they are not changed like Benson is thinking [See 'The Cacti of the United States and Canada' page 917]. I have seen the plants in fairly thick scrub brush, in grassy areas with the occasional bush and in an area that some one had bulldozed the ground and made it level like a landing strip. However, there was no indication that it had ever been used for landing a plane. The area was about 12 metres wide and I do not know how long. The Micropuntia pygmaea were thick there, I would say from 5 to 25 plants per square metre. Quite a few plants turned out to be clusters of seedlings growing where seed pods dropped their seeds. I am going to hazard a guess and say that it was because the ground was flat that the seed pods did not roll far and the seed germinated in clusters.
As to how the plants grow, the Micropuntia have a large underground water storage root, these roots are carrot like in shape. They are from a few cm long in young plants to about 10 cm in older plants. In the ones that I have seen the bottom of the root is as though it was sliced off. Out of that flat bottom grew the food and water gathering roots. From the root to the surface of the soil there is a long neck or trunk like growth. It can be up to 14 cm long. That carries what ever is need from the roots up to the plant stems that are just above the soil level. Fig. 1 shows the plant from the top of the root to plant tip. Fig. 2 shows the top of the neck and what would be the above ground growth. Actually that area above the start of the stem splitting could also be under ground; where the green stems are growing out at an angle would be about soil level in habitat. For me, the plants start showing growth in mid to late winter. The plants in habitat that I have seen are only about 2 to 7 cm tall. The taller ones were single stems or at the most two stems. The shorter plants were several stems from the one root as in Fig. 2. Figs. 3 and 4 show a different plant to Fig. 2. Both of these two plants are kept growing all year and so have more plant stems than habitat plants. In habitat the plants bloom, set seed and then appear to have gone as the stems disappear. If you go in the early spring, when the plants are in flower, you can see plants all over the place. Go later on in the summer and you will not find a single plant. Some of the stems could very well be harvested for water later on in the summer by mice or rats. So actually you could say that the stems of the plants above ground are annual and the underground roots and root stem are perennial. However, from what I understand, Micropuntia barkleyana keeps its above ground stems all year long.
Fig. 1. Micropuntia pygmaea Wiegand & Backeberg
Fig. 2. Micropuntia pygmaea. Above ground stems.
In habitat, ground level would be at start of secondary stem level.
Fig. 3. Micropuntia pygmaea neck/trunk.
Fig. 4. Micropuntia pygmaea. Above ground stems with buds.
As a possible consequence of keeping the plant in Fig. 3 growing, besides putting on the new growth on top of the older trunk, the plant has also grown another trunk out of the root top and that trunk has three stems on it. The new trunk is still semi-green but should harden off before the season is over.
The third consideration is the rain fall pattern in habitat. In the winter, starting about December, the area receives some rain. Then it goes into snow. I have heard of at least over a metre of snow on the ground and lasting sometimes for a month. The air is quite dry making the snow actually evaporate instead of melting. Usually from about mid April till even into August there is no rain. In the area where I have seen the plants, when the monsoon rains hit they are quite violent. They are thunderstorms that really throw the lightening around. There can be hail and also lots of water. Flash floods are common in the areas. I have to think that it is the absence of rain from April till about mid July that influences the plants to only grow seasonal stems. The stems are there long enough to bloom, set flowers, make seed and then are gone.
The photos shown in Figs. 1 and 2 are of the same plant. Fig. 1 shows the top of the root, the root stem and what would be the above ground growth. From soil level to the tip of the bud the plant is 13 cm. From the stem split to tip of bud is 6 cm. In habitat from just above the split of the stems down would all be underground. Only 2 to 7 cm would be above ground and that is only temporary or seasonal. My tallest plant is, roots and all, 26 cm. Notice that the buds are terminal, that is they are growing out of the end of the stem. Once that stem has bloomed it will not bloom again. In habitat I saw no signs that the stems fall off, blow around and then take root. Indications were that all the plants I saw were seed grown. On the flat ground, mentioned above, there were clumps of plants that were seed grown. The seed hulls were still to be seen beside the plants. There were no rooted stems that were laying on the ground. When that stem finishes making seed, if it does, it is then to be dumped as waste. Taking this into consideration I have come to the conclusion that in cultivation my plants do not lose their stems due to the growing medium I use or what ever else I do to it, but they are just doing what has been done in habitat for eons. However, there is one thing that I did for the plants that they did not like, and that was giving them alkaline water. Also they do appear to like a mineral based soil rather than a humus based one. To grow the plant like it grows in habitat, a pot about 30 to 36 cm deep and 12 to 15 cm in diameter would be needed. That would hold the plant and allow the root to grow and thus take on needed water and nutrients. However, since I do not have pots that deep, I have the plants planted with the root neck raised above the soil in the pot.
Backeberg lists six Micropuntia names: M. barkleyana Daston, M. brachyrhopalica Daston (T), M. gracilicylindrica Wiegand & Backeberg, M. pygmaea Wiegand & Backeberg, M. tuberculosirhopalica Wiegand & Backeberg and M. wiegandii Backeberg. I will go along with three of them: Micropuntia barkleyana, M. pygmaea and M. wiegandii. If you go back and look at Fig. 2 you can see that the stems are really quite short. The description of M. pygmaea is that it has short stems up to only about 2.5 cm long. Charles Glass did not recognise M. pygmaea but did recognise M. gracilicylindrica. The description of the latter plant calls for stem segments to be up to 20 cm long. Note that the stems can be up to 20 cm long but it does not say they have to be that long. The same with the stems on M. pygmaea, they can also be shorter than 2.5 cm. Figs. 5 and 6 are of the same main stem. The flowers are different. The terminal flower was the first flower to bloom and the flower that looks to be coming out of the side of the stem is blooming today. The stem on which the flowers are blooming is 11 cm long. However, higher up the plant from the flower the stems are much shorter. But it could still be M. gracilicylindrica because the stems can be to 20 cm long or they can be shorter than 2.5 cm. The first time I ran into these plants I was out with the Sclerocactus Study Group from Europe. They had been visiting the plants for I do not know how many years. They did not think there was any difference in M. pygmaea and M. gracilicylindrica and neither do I. The reason being is that I have several plants from central Nevada and one year they can fit the description of M. gracilicylindrica and the next year they can fit M. pygmaea. I think this is caused by the growing season, for one year they will start growing quite early before making buds. The next year they may not grow any stems until late and then they bloom on short stems. Notice that the plant in Fig. 2 has buds on it and that is on short stems. So if you did not study the plants closely you would say that the plant is M. pygmaea. The plant in Figs. 5 and 6 you would assume to be M. gracilicylindrica. A few times I have changed the name back and forth until I discovered that one year they will grow long stems and another year they will grow only short stems. As I have seen the plants grow differently from year to year I have to agree that the two plants are the same species.
Fig. 5. Micropuntia pygmaea terminal flower on a main stem.
Fig. 6. Micropuntia pygmaea flower on a secondary stem.
Quite a few authors seem to think that all the Micropuntia are nothing but Opuntia pulchella although Backeberg and Glass listed some of them as different species. Still many people think they are one and the same plant. If you look under Grusonia pulchella in Anderson’s book, The Cactus Family, you will find all the names of Micropuntia listed as synonyms under G. pulchella. In the NCL you will only find pulchella under Corynopuntia with no mention of any of the other Micropuntia at all. Glass did not think they were one and the same species. Under Opuntia pulchella he mentions a very large difference in the plants. That is the tuberous root. He says, “A clump-forming species arising from a glochid covered tuber 2 – 3 ¼ inch in diameter”. Some years ago some one gave me two of the plants and they were nothing to fool with. The roots were thickly covered with 3/8 to ½ inch long glochids. The roots were about 8 inches long and were shaped like a parsnip. The two plants I was given were bare root and the roots were about 3 inches in diameter at the neck. I had never seen a M. pygmaea with glochids on the root before, but seen them only now and then at the neck.
The flowers are up to 2.5 cm in diameter and they last only about half a day. Mine have opened around noon and close about five hours later. The flowers change colour. In the first hour or two the flower is a really dark colour but as it opens all the way it lightens up a bit to the colour of the flowers in Figs. 5 and 6.
This article was originally published in Tephrocactus Study Group (the 'TSG Journal'), September 2011, Vol. 17, No. 3, pages 34-36 and 41-43. © TSG and Elton Roberts