Hi Mike, you certainly come up with interesting and complex questions and more power to your elbow (or is it fingers these days?) You have covered a fairly broad spectrum of the Mesembryanthemaceae. None of the species you mention should cause undue problems with their growing conditions. It is knowing what these growing conditions are that is the problem, because they are many and varied,
The first thing to take into consideration as a general rule is that they will continue to grow as they would in their natural environment. With that in mind many of them are in full growth in autumn and early winter in the Northern Hemisphere. So when you are tending to cease watering your normal cacti, etc. these plants will need normal watering (how much depends on the species) starting to hold back on the water at the end of December.
I would start to water my Lithops in June and my Pleiospilos in July, also around that time Conophytums. The name for the offsets of these plants is 'heads' rather than pups.
The most important thing with this type of plant that forms heads is that grown ideally there should never be more than one pair of leaves (the pair of leaves form the head). The plants that have one pair of leaves on top of another pair of leaves, on top of another . . . etc. etc. are not being grown correctly.
This is where it becomes important to know the growing cycle of the plant. We will use the Lithops as an example, as they are quite common and popular: On the face of it they would seem to have quite a short growing season. We start to water them probably in early June. Most have flowered by September. After they have flowered we cease to water them and to all intents and purposes they have gone into dormancy, when in fact there is nothing further from the truth. Within each individual head of the Lithops a new replacement head[s] is forming. This will probably start to show itself in late winter by poking through the old head (usually at right angles to the fissure between the two leaves of the old head). Many people think at this stage that the plant is springing into growth and should be watered. No, no, no a thousand times no. There are still several months before watering should commence.
What should be allowed to happen is that the new head takes all its nourishment and growing power from the old head, which will eventually be 'sucked' dry of every last bit of nourishment it can give the new plant and will end up as two papery shells either sid e of the new head. Then and only then should watering commence. This is a good general rule for all the 'head' type plants.
The above photograph is a reasonably good example of wbat I mean: The green Lithops albinica at the bottom right has completed the cycle. If you look closely the old heads are just white paper husks clinging to the new heads, whereas the purple optica rubra next to it is not quite there yet. The old heads are starting to shrivel but the cycle is not complete. This particularly Lithops has a later growing season than most of the others.
One of the big advantages of growing this type of plant is that you get a complete new unblemished one each year. Wouldn't it be wonderful if that old scarred and gnarled Ferocactus with the odd spine missing here and there, regenerated itself in the same way?
I could go on and on but am even starting to bore myself, so I hope that is of some help Mike.
John
