Re-rooting Maihueniopsis -- advice, please!

[Steve Johnson]

Very unusual cactus, hard to find here in the US -- and I may have the opportunity to acquire a Maihueniopsis (AKA Puna) clavarioides. If this happens, it'll come from C and D, but unfortunately the plant lost its roots. I'll have to try and re-root the clavarioides when the growing season begins, and since I have zero experience with the species, I'd like some advice on the mix that'll be appropriate to the nature of its root behavior. These are my options:

1. Pumice-decomposed granite mix -- fairly coarse mineral aggregate with grain sizes ranging mostly from 1/32" to 3/16". I thoroughly rinse the mix before I use it, so this is a truly soil-less mix. Works incredibly well for the vast majority of the cacti I have in my colection.

2. 50/50 pumice-soil mix -- soil-less mix won't support the very fine roots of my Tephros, but they really perked up once I made the change.

3. Pumice-DG with some soil mixed in -- mineral-to-soil ratio is about 80/20. I use it for my Melocactus matanzanus and 2 Discocactus (buenekeri and crystallophilus).

If someone with solid experience growing M. clavarioides can tell me which one of these mixes should work best, I'd really appreciate it.

Thanks!

[Robb]

I haven't had any experience with the species in question, but I would be leaning towards the 50/50 ratio. A member of my local CSS society grows the species quite well using a similar mix to this one. His mixture consists of a 65:35 mixture of large grade pumice and regular potting grade soil.
Hope this helps!

[DaveW]

I easily rooted a cutting I was given many years ago and still have the resultant plant below. In those days it would just have been planted in the then UK standard John Innes No. 2 potting compost with one third extra grit, long before ever the mineral soil cult for cacti started. Potting compost in the UK simply means a potting soil mix, not the other meaning of composted rotting vegetable matter. As many in the US may have never heard of JI Composts we in the UK sometimes mention, here are the recipes. However inferior peat free versions are now being sold at garden centres in the UK which are not much use for cacti since they contain rotting composted garden waste, since due to the green lobby complaints of decimation of peat bogs the UK is becoming anti-peat for horticulture. Good loam is also hard to obtain in the UK since most now sold is just garden (yard) soil from building sites these days. The best virgin loam was originally the top spade depth of soil from unploughed meadow land, with the turves stacked upside down until the grass had rotted, now that is as rare as hens teeth in the UK, hence mineral mixes for cacti often used instead:-

http://www.gardeningdata.co.uk/soil/joh ... _innes.php" onclick="window.open(this.href);return false;

As you can see JI composts were peat and soil based, therefore I doubt any special potting medium is needed to root clavaroides since I have always found the plant tough as old boots, even thriving in a cold greenhouse over winter. It is a tuberous rooted plant though, so like other tuberous rooted cacti it may appear to stand still for a year or so, not making much in the way of top growth, with all the growth taking place underground until a tuber has formed. In habitat it regularly looses the top growth, regenerating from the tuberous root, but does not seem to do this in cultivation.

Opuntia clavaroides.jpg (72.25 KiB) Viewed 940 times

[Steve Johnson]

Thanks for your feedback, gentlemen! What you said was very helpful, and it confirms my intuitive thought about going with a pumice-soil mix. The Tephro species I grow don't have taproots, so the soil in my 50/50 mix keeps their very fine fibrous roots happy. However, because M. clavarioides does have a taproot, I'm inclined toward something more like a 70/30 pumice-soil mix. Your comments tend to back up my belief that the fibrous roots growing out of the taproot may be Tephro-like in their fineness. If I'm correct, then a more open mix should satisfy the taproot while it provides enough soil to stimulate regrowth of the plant's fibrous roots. 70/30 sounds about right, although we don't have to be too precise about it, do we?

My acquisition of the clavarioides isn't a done deal yet. But if and when it is, I'll post up a little presentation with photos.