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Hello all!

I have a batch of several species that are a few weeks over 1 year old. They're growing well, but the problem is that in my inexperience at the time I potted them in 50% sphagnum peet moss (remaining volume is 25% pumice, 25% Turface), and the substrate has become so hydrophobic that getting it to rehydrate is becoming more and more of a pain in the neck. On top of that, the substrate has compacted down to about 50% of the original volume and is basically just a freaking brick.

Basically I'm wondering if they would suffer any negative effects from getting re-potted into a more suitable substrate when they're so young and small. I'll be honest, I can't see myself getting them out of these bricks of sphagnum without tearing their little roots to hell.

I have the following species:
Ferocactus cylindraceus, Ferocactus wislizenii, Ferocactus viridescens, Echinocerus engelmanii, and Mammillaria dioica.

Here are pics, in case that helps. The seedlings are plus or minus about the size of a dime.
Additionally, I've got some Echinocactus polycephalus seedlings that are struggling in the same growing medium. These ones I'm really hoping it's safe to transplant, because the substrate is so dense and gets so soggy that every time I water them another one or two rot and die. Honestly, I'm at the point where I think their only chance of long-term survival is to get them in a better draining mix.
Even if they all die from being transplanted that's not the end of the world. I have about 150 E. polycephalus seeds in stock to give it another try this year with a better substrate. I'd hate to see a year of work and care go down the drain, but it is what it is.

Yes, you should get them out of that stuff. When it's warm enough for them to take water (might be now where you are), I would soak them in warm water a few hours or even overnight to soften up that mix. A bit of soap in the water as a wetting agent could help.Then you should be able to separate them without too much damage and rinse the roots clean. I'd spread them out on paper towels to dry after that, and let them heal a while before potting them.

greenknight wrote: ↑Sat Mar 09, 2024 8:03 am Yes, you should get them out of that stuff. When it's warm enough for them to take water (might be now where you are), I would soak them in warm water a few hours or even overnight to soften up that mix. A bit of soap in the water as a wetting agent could help.Then you should be able to separate them without too much damage and rinse the roots clean. I'd spread them out on paper towels to dry after that, and let them heal a while before potting them.

Thanks Spence, the tip about the soap sounds really helpful!

They've been inside under a grow light all winter at room temp, so they're awake and have been growing since I planted them. Still too cold at night for them to be outside, but when it gets warmer I was planning on introducing them to the great outdoors with the rest of my collection (under shade cloth of course).

Well I started the unpotting. Considering that they're the ones actively dropping like flies I started with my Mammillaria tetrancistra and Echnocactus polycephalus. Yesterday I soaked the containers in water with a few drops of dish soap until they looked as saturated as I could get them, then left them overnight to soften. I think the dish soap worked really well! Getting the peat moss of them and cleaning them up was not nearly as bad as I thought it was going to be. Still, I couldn't get every last bit of substrate off the roots without causing excessive damage, but I got >90% in all cases.

I don't know what else I can say about the Mammillarias, I don't think they'll survive. For being a year old they're about the size of a pencil eraser and just look... not well. Really pathetic roots. I planted 50 seeds from Mesa Garden and initially I was super excited because almost all of them germinated, but I only have three surviving: 94% casualty rate.

The Echinocactus look a lot better, but to my surprise I found ROOT MEALIES! Freaking hell. I'm already dealing with an infestation in my main collection outside, and my seedlings have lived inside under a grow light their entire lives.
My 11 surviving seedlings do look pretty good all things considered. After cleaning the roots I liberally soaked them in insecticide soap and am letting them dry under a ceiling fan. I originally planted 75 seeds from Rob Romero's Etsy shop and about a third of them germinated.

Gonna keep going with the rest of the seedlings. Hopefully I don't find any more pests.

Root mealies - yikes! Definitely need to kill off those.

Otherwise, looks good. Plenty clean enough, retained lots of roots - in fact, I think you need to trim some of the really long roots.

The ones that are struggling may perk up when you get them in a better medium, wish you luck.

greenknight wrote: ↑Wed Mar 13, 2024 10:02 am Root mealies - yikes! Definitely need to kill off those.

Otherwise, looks good. Plenty clean enough, retained lots of roots - in fact, I think you need to trim some of the really long roots.

The ones that are struggling may perk up when you get them in a better medium, wish you luck.

Thanks, Spence. These guys have struggled ever since they germinated, but E. poly is my favorite cactus species so I'm really committed to learning to grow them, difficulties and all.

I unpotted my Ferocactus wislizenii last night and did not find any mealies. Still working through the rest of the species.

You should give them all the insecticidal soap treatment whether you can see mealies or not - the mealybug nymphs are just specks.

greenknight wrote: ↑Thu Mar 14, 2024 9:16 am You should give them all the insecticidal soap treatment whether you can see mealies or not - the mealybug nymphs are just specks.

Oh for sure. That's what I was doing with every plant in my main collection, and it made sense to do the same thing with the seedlings.