How tall can a sheldonii grow?

When we get plants into our collections we don't always forsee their height over the time. My m. sheldonii has been as a seedling on my windowsill since 2005 or so; I'm happy to see its showy blooming each summer, but its height... The net info says it can be 15cm tall (up to 25cm?). Mine is about 18cm already which makes it bend from side to side and it doesn't make me happy. How tall are yours, I wonder? What is the existing limit that I should expect?

It is difficult to say how tall your plant will get, but for most species related to M. sheldonii (the Ancistracanthae) a height of 15-20 cm is given as maximum in books. My oldest M. fraileana, sown in 2000, is now 40 cm long! It has a few offsets, but the main head is still looking healthy and flowering profusely every year. Yet, because of its length, it has bended over, the upper part resting on a support.
Another example in my collection is M. moelleriana. Pilbeam writes in his Mammillaria book: "at most to about 13 cm tall" and "11 cm tall or more". My very old plants are more than 25 cm tall.
So the answer to your question "How tall can a sheldonii grow?" is probably something like "It will get as tall as it gets old".

Wolter ten Hoeve.

Thank you for your comment, Wolter. I wish I could have a look at your m. fraileana and m. moelleriana patriachs. Does Pilbeam's info show that he talks about nature plants concerning their height? And here me come across another question: how long do these species live - in the wild and in cultural spots? My plants are too young to be a source of such data, unfortunately... And how can one define the approximate age of plants (=cacti) in their habitat?

A year ago I took photos of 2 old moelleriana/cowperae. See the photos. The plants are 30-35 years old, if I remember well, all seed-grown. The moelleriana has actually been taller, but a few years ago I repotted it and buried part of the ugly lower half into the substrate. But even now, the plant cannot keep its body straight.
Also attached is a photo of another, almost as tall moelleriana, which had started dividing dichotomously several years ago. That plant died this winter due to rot in its top.
In nature, they absolutely don't get so tall. I have seen both moelleriana and cowperae in habitat, and I estimate that all of those plants were certainly less than 10 cm high. I assume that they don't get very old in nature.
I have never been to the Baja, so have never seen fraileana in nature.
Let's see if I can take a photo of my tall fraileana tomorrow.

Wolter.

Here is a photo of that very tall fraileana, in a 10 cm pot.

The cowperae in my previous message was sown in 1988, the moellerianas were probably sown a few years earlier.

The age of a plant in nature is very difficult to estimate. A plant in a favourable position will grow much faster than a plant in an unfavourable postion. A long drought may kill plants, a strong frost may kill plants (in 2011 there was a strong frost in the Torreón region, it became -18 Celsius in Viesca, thus killing many cacti; this was called the 'helada negra', the black frost).
FitzMaurice once told me that many years ago there had been a very strong frost in much of the northern half of Mexico (1957?) and that certain populations were completely wiped out. Thanks to seeds still present, several of these populations recovered, but that took decades, according to FitzMaurice.
I think that it is easier to estimate the age of a large columnar or barrel cactus than the age of a small mammillaria.    

Wolter.

One should expect at least 30 cm height or rather length from cultivated plants of M. sheldonii or M. gahamii. Many of these branch freely and this reduces the height and without support stems lean or crawl on the ground.



Habitat plants are more compact especially under full sun.

Hello Wolter. Thanks for the senior cactus images - they could never have got this tall in habitat! Talking about weather extremes in Mexico - are there any researchers who monitor cactus spots, especially being pretty rare in habitat? They might conduct records on those populations...
   Thanks for your photos, Agrippa. Now I can hope my sheldonii will branch someday, too.
In case the habitat photo was taken by you, were the localities (if there were more than one) similar concerning their climatic characteristics and the plant heights?

Olegg wrote:

...
In case the habitat photo was taken by you, were the localities (if there were more than one) similar concerning their climatic characteristics and the plant heights?

The last photo is taken in Phoenix and pictures abundant M. grahamii ssp. grahamii. It is everywhere in rocky parks in the city so it is known to everybody there.