FAQ (Frequently Asked Question)

- 1 - What are Field Numbers?
- 2 - Recommended Mammillarias for Beginners?
- 3 - What does the spiral arrangement and their numbers mean?
- 4 - What are Areoles, and Why are they Important?

1 - What are Field Numbers?

Field Numbers are a way of identifying plants in the field. A field number consists of some letters followed by numbers. For example, ML 36 refers to a plant or seeds that were collected or identified by Michel Lacoste,and it was his 36th plant to be officially identified. Another example of a field number might be Lau 065, which identifies the collector Alfred Lau, and it was his 65th official collection.

The Field Numbers are officially recorded, and normally carry additional information with them. ML 36 was identified as Mammillaria Kraehenbuehlii, and it was specifically found in the state of Oaxaca, Mexico. More specifically at Tamazulapan, Santiago Teotongo, road to Conception Buenavista, 2200m.

So as you see, not only does the field number tell us the species, but the specifics on its location in nature. In this case, it includes the elevation of 2200m.

By having plants or seed that are identified with field numbers, the Mammillaria grower can be assured of having an actual species, and not a hybrid plant.

So if you find two Mammillaria of the same species, and one has a field collection number, and the other does not, chose the one with the field collection number…it will be the real species rather than a possible hybrid, and in choosing plants with collection numbers, you encourage nurserymen to propagate plants like those in habitat.


3 - Recommended Mammillarias for Beginners?

There are many species of Mammillaria; some of them are considerably easier to grow successfully than others. Mammillaria grow across a wide range of habitats in nature, and therefore each species has its own growing requirements in cultivation.

In the recommended list below, those cacti which are particularly demanding in light, temperature, and soil requirements have not been included.

When considering which Mammillaria the new or inexperienced cactus fancier grower might want to consider, the following list comes to mind:

Mammillaria albilanata, backebergiana, baumii, bocasana, bombycina, canalensis, chionocephala, columbiana, compressa, decipiens, discolor, duoformis, elongata, fittkaui, formosa, geminispina, glochidiata, haageana, hahniana, heyderi, karwinskiana, laui, longimamma, magnimamma, marksiana, matudae, melanocentra, microhelia, mieheana, morganiana, muehlenpfordtii, mystax, oteroi, parkinsonii, perbella, petterssonii, pilispina, plumosa, polyedra, polythele, prolifera rekoi, rhodantha, schiediana, scrippsiana, sempervivi, senilis, sonorensis, sphacelata, sphaerica, spinosissima, standleyi, surculosa, vetula ssp gracilis, voburnensis, wagneriana, and zeilmanniana.

Please note that some of these species are not common in garden centers, and the cactus fancier may need visit a cactus nursery for the uncommon species.

In the United States, the following species are often available in garden centers: bocasana, bombycina, elongata, haageana, magnimamma, microhelia, muehlenpordtii, prolifera, rhodantha,spinosissima, and zeillmanniana. A friend tells me that the folowing species are available in garden centers in Europe: bocasana, bombycina, backebergiana, elongata, geminispina, hahniana, microhelia, prolifera, polythele, spinosissima, vetula spp. gracilis and zeilmanniana.

Please examine any plants that you buy for pests, especially mealy bugs above and below the soil level. This will greatly increase your chances for a good growing experience.

For any Mammilaria species, growers are highly encouraged to find out the particulars of the species in question. These are available in a number of publications; one is most likely to find these specifics in books that are devoted to Mammallaria.

Good Growing!


4 - What does the spiral arrangement and their numbers mean?

One of the main attractions of the genus Mammillaria is the very precise symmetry of their growth. We have all marveled at the precisely positioned spirals of tubercles that one can see, especially if looking directly down at the top of the plant

The raison for this growth pattern is simple in concept, but hard to explain. So to understand this, lets imagine looking at a normal plant and how its leaves are positioned on the plant stem. An examination will reveal that the leaves are produced in a spiraling alternate arrangement, with each new leaf being set a fixed number of degrees from the leaf just below.

If we imagine the stem of an ordinary plant being shortened, we can then arrive at the arrangement of leaves on plants like the Agave, which form rosettes of tight leaves. Now think of the spines (modified leaves) and the tubercles that they rest on. It becomes clearer that the spiral arrangement is simply derived from the ancestral spiral leaf production in whatever plant group developed into Mammillaria. Each new tubercule is produced at a set number of degrees from the last tubercule.

Mammillaria variaculeata

An interesting feature of these spirals is that they have very precise ratios of the number of spirals when counting clockwise and when counting counterclockwise. As wonderful as Mammillaria are, they simply are following a set of ratios that were first described by the Italian Leonardo Fibonacci (c. 1170 to c. 1240). He had never heard of Mammillaria, but he was interested in the mathematical description of spiral structures found in many examples in nature….such as the snail shell and the nautilus shell. When Mammillaria became available, growers and scientists begin to apply Fibonacci’s ratios to these plants.

Mammillaria chionocephala

In Mammillaria, tubercules are arranged in spirals downwards from the growing center in spirals in both clockwise and counter-clockwise directions. There appears to be a grouping of these spirals in a predictable series of progressive mathematical steps which have set relationships within that series as well as between the various series. In the first series with the smallest number of tubercles, there are 3 spirals in one direction and 5 in the other, with a difference of 2 between the two rows; in the second series there are 5 and 8 spirals with a difference of 3; in the third series there are 8 and 13 spirals with a difference of 5. You can see that when the amount of the differences between the spirals of the first two series (3 and 5=2) and (5 and 8=3) are added together, the sum will be equal to the amount of the difference between the spirals of the third group (8 and 13=5). The fourth series is 13 and 21 with a difference of 8 or the sum of the differences of the third and second series. The same is true of the next series of 21 and 34 with a difference of 13 which is equal to the sum of the two fourth and third series, etc.

These relationships continue for larger and larger numbers. We have summarized these relationships below:

3 and 52
5 and 83
8 and 135 (2+3)
13 and 218 (3+5)
21 and 3413 (5+8)
34 and 5521 (8+13)

When we look at three examples (Mammillaria variaculeata, M. chionocephala, and M. supertexta, the numbers appear as such:
-Mammillaria variaculeata - 8 and 13
-Mammillaria chionocephala - 13 and 21
-Mammillaria supertexta - 16 and 26

In our actual example, M. variaculeata and M. chionocephala follow the rules, like the larger part of Mammillaria species do. However, there have some other series been reported, like this M. supertexta with 16 and 26.

Mammillaria supertexta

Some of these "odd" series are :

7 and 125
10 and 166
11 and 187
16 and 2610

Some plant taxonomists have considered the number of spirals to be important clues as to a plant’s identity. Other taxonomists do not. An interesting footnote is that the number of spirals in each direction can change as the plant grows larger, but they usually retain set ratios between the number of spirals clockwise and counterclockwise.

The reason that these growth patterns exist is for a variety of reasons; probably the best explanation is for the most efficient spacing or packing of growth tissue. Regardless of the reason, in Mammillaria, the result is a wonderful symmetry that appeals to the eye and mind.

If you are interested in finding out more, may I recommend The Cactus Primer, by Arthur C. Gibson and Park S. Nobel, especially the information on pages 118 – 121. Also recommended is ‘The Mammillaria Handbook, by Robert T. Craig.

5 - What are Areoles, and Why are they Important?

As you know, Mammillaria have spine-bearing areas called areoles. The word areole comes from the Latin "areola", meaning a small area. These are the furry pads at the tubercle tips that are familiar to us all.

Long ago cacti’s ancestors begin to shorten the interleaf spaces. Associated in the axil of each leaf is a lateral meristem (tissue that can continue to grow, and give rise to branches, flowers and leaves). In cacti, this lateral meristem became the place where spines, offshoots or branches, and flowers are produced .it became the areole. See the pictures of Cereus and Ferocactus

left: Cereus - right: Ferocactus

In some cacti, the meristematic tissue is all located on the very visible areole. A ceroid or candle cactus is an example of this. You can expect spines, offshoots, and branches to all come from the visible areole, and in some cases, the production of spines may continue for some time at the same areole. In Melocactus there is a proliferation of areole, with virtually no spaces in between. This gives rise to the terminal cephalium found in that genus.

In some globular genera like Mammillaria and the related genus Coryphantha, interesting developments have occurred. Part of the meristematic tissue has moved from the tip of the tubercle where spines are produced. In Corypantha, there is a visible groove on the top of the tubercle, and it runs down to the axil. Flowers and offsets can be produced from this groove. So the areole has become elongated, with meristematic tissue running down this grove. See the picture of Coryphantha elephantidens.

Coryphantha elephantidens

However, in Mammillaria, all of the meristematic tissue that produces spines is located at the tip of the tubercle, while the meristematic tissue that produces flowers and offsets is located in the axil. In a very real sense, Mammillaria have split their areole into two completely different sections one to produce spines, and the other to produce flowers, wool and offsets. See the picture of Mammillaria sp. Tlayecac.

Mammillaria sp Tlayecac

So Mammillaria represents an evolutionary development of the areole that contains the meristematic tissue which produces spines (modified leaves), offshoots (new branches) and flowers.

Take a close look at your plants next time
you may see some wonderful things!