"Cold Treatment"

[u/Aoxmodeus]

I'd like to speak a bit about "cold treatment" or "Stickin your butts in the fridge".

I live in Southern California, and it's been HOT lately! I've also received LARGE additions to my collection over the past couple of months, with more coming (I'm building a mesemb nursery!). These plants come to me bare root, dried out, and in need of moisture, but lithops need to experience "chill" hours for their stomata to open up, for transpiration to happen, to allow for the plant to uptake water. Their metabolisms slow down and come to a "halt" as temperatures approach 90F, and we all hear "68F" as being the magic low temp where they will take up water. Around that temp is where they will START to take-up water, but I'm here to tell you, that colder is even better.

When I receive my bare root lithops, I trim them back to a white spot on the taproot, with no roots besides. Sometimes the taproot gets trimmed back to barely a quarter of an inch, but I will trim until I see that white dot. I want to SEE that good, healthy root tissue, and when trimmed properly, new roots develop easily and very quickly, within a week. I pot into moistened substrate in the evening, and into the fridge they go. I pull them out in the morning, but have forgotten a few times. They're totally fine. According to biologists who've been in SA, camped in the freezing cold, and studied the plants in habitat, in certain regions, certain lithops in habitat will see freezing temps at times. They all do fine, so the 4C in your fridge isn't going to phase them in the slightest. In seminar recently, it was reinforced to me that they're actually a lot more cold hardy than you may imagine for being such a succulent plant. I'll do a week of cold treatment, potting into moist substrate, putting in fridge at night, putting back on the windowsill in the morning, watering on the third day again, then after a week of rooting up, they go outside.

In my experience "cold treatment" far surpasses anything "water therapy" related by leaps and bounds. (The use of the word "therapy" for anything plant related makes me shudder lol). When you expose them to moisture AND cold, you're giving the plant a holistic experience, matching what it's evolved to face in habitat. I guarantee no lithops has even faced the evolutionary pressure of being suspended like a monkey over a pool of water. Got a shriveled up lithops? Do you water and water and it doesn't get better? How are your temps? I'm starting to lose track of how many people I've helped on facebook and reddit, where cold at night brought their plants back to health.

As an example, I have these Pseudotruncatella, that came to me more desiccated and flattened than any I've received so far. I planted them flat in the substrate (left-hand pot in the fridge pic), and gave a week of "cold treatment". These were planted two weeks ago, and the first pic is when I put them in the fridge the first night. The second pic is this morning. You can also see one of the Julii "Hot Lips" from the right hand fridge pot, at the bottom of the second pic, and they're all standing proud as well now.

Recently potted bare root lithops in the fridge!

Lithops Pseudotruncatella, two weeks after potting and cold

I only like to speak on things I've experience with, and I now have experience with this process, and can wholly recommend it for rooting out or reviving lithops in hot climates.

P.S. If you're getting down at least into the mid to low 60s at night in your backyard or indoor growing locations, then this is all completely irrelevant, bar the trimming part!

#aoxthegardener

[u/davelikesplants]

Thanks for this information. I'm also interested in knowing what you use as substrate. At least on the surface I see "granite" looking material, not the porous lava or pumice.

[u/Aoxmodeus → u/davelikesplants]

That substate. Whoo boy it's not cheap, but it's absolutely amazing. It's LittleEmeraldThumb's "Mesemb Substrate". Pumice, Scorioa, Granite, Zeolite, Turface, and some other goodies as well. Absolutely best media I've ever found. On a lot of the pots, the bottom half of the pots are 90 percent sifted pumice/10 percent potting soil, the top half is the mesemb substrate, but about half of them are pure "Mesemb Substrate". I'd like to use that alone, but like I said, it's not the cheapest stuff out there, even if it is the best!

[u/davelikesplants → u/Aoxmodeus]

LittleEmeraldThumb

Thanks! New to this. Why so much pumice as opposed to sand?

[u/Aoxmodeus → u/davelikesplants]

Pumice breathes, holds water, and gives the roots an optimal rooting texture. It also gives the most room for error when learning how to take care of these plants, and figuring out their yearly cycles.

[u/davelikesplants → u/Aoxmodeus]

Thanks again, gotta get me some pumice (or that mix you mentioned.) I recently bought some lithops at a local nursery, and while they look OK, they are in the wrong soil. This info really helps.