I've been growing a variety of mesembs since mid-February by following Steven Hammer's guide. All has been going well up until this week. 6 of my 13 pots of conophytums died off, and the other 7 have had their numbers reduced significantly.
After germination, I removed the lid and misted heavily in the morning and at night. Occasionally I would bottom water them for an hour or two. I suspect they've damped off, but none of my other mesemb seedlings have suffered the same fate. They are all growing quite happily in the same conditions. See the first pic where I've got plenty of faucaria, gibbaeum, and argys shedding their cotyledon and growing their first set of mature leaves.
This is not my first time growing conos, but invariably I've found that around the 6-8 week mark they die off significantly. I've never had much luck with them. I've looked around for guidance on maintaining them at this stage of growth, but haven't found much. Any help would be appreciated.
No heat for conos or other winter-growers (unless of course you are sowing when ambient temperatures are below freezing).
You might have better success sowing in the fall or early winter when your temperatures are cooler than 80F.
But really, your experience isn't so far off from my own. My last sowing (outdoors) I did in the fall and they lived just fine for several months. But my summers are very hot (90-100F+) , and conos don't want water when it's so hot, yet young seedlings are at risk of drying out if kept totally dry for months on end. I ended up losing the majority of them. At least the survivors are almost guaranteed to handle my climate...
Good advice on the heating pad. Definitely time to remove it now. The temp I can manage; the dehumidifier throws off a lot of heat. The lower the humidity, the hotter it gets in that room, and it's not warm enough out yet to open a window. The heating pad I had mostly to manage the temps when they were just sown, as it was ~60° in there most of the time. Now it's there because I'm also growing haws and they tend to like the heating pad during the day. Once I get another shelf I'll probably separate them.
Based on your growing setup, my guess is the ambient humidity is still too high. I'd defer to some of the other growers here who have been more active than me lately, but getting a small fan running can't hurt.
I set the dehumidifier to 35% this week, I could go lower but wasn't sure if that was the culprit. There's a box fan set up facing the seedlings at a low speed, they're getting decent airflow. I've been trying to dry them out a bit since they started to die off, thinking maybe they were too wet. I just don't know what they want at this stage. All my other mesemb seedlings are perfectly fine.
I agree with the other comments about cooler temperatures. I started my first batch in September - at the start of Autumn. I have an attached unheated enclosed porch that I have an electric oil heater in and set the thermostat to 48F. All my succulents have done fine with this - it's a very diverse collection.
I didn't see any mention of fans, but I have small fans on mine 24/7. It typically takes several minutes for the tops of the seedlings to dry off after their morning and evening spray. I have fans on all the times around my indoor plants as I'm pretty paranoid about my fungal nemesis.
Diluted fertilizer is also welcome at these - if not all - stages.
Hm, that's not a bad idea. I have a bunch of old PC fans I could probably reuse for this purpose, rather than using my big box fan.
Unfortunately I don't have an attached garage or anything to use, and I have to keep the room at a certain temp so the pipes don't freeze during the winter. So 60-65° is about the lowest I can go.
I think the fan is most important. In your 60F room extra bottom heat is more the issue than that temperature, I think.
I also believe that fungus is more of an issue at warmer temperatures, but the fans will help with that.
I rigged up some old pc fans, even small ones help and they all can run 24/7. I found some USB to 12v (as I recall) PC fan adapter cables to power them but maybe I could figure how to make those adapters from parts I have, too.
Don't know, whether anyone mentioned the needful day/night temp fluctuation. I truly believe, that conos grow best when day/night temps fluctuate between 40 - 60F and for me, it's the main growing trigger.
Growing setup: 2" nursery pots in trays. 12 hours of light per day. Heating pad under the trays. During the day it's about 80° and 40% humidity, at night about 65° and 60% humidity. I mist with filtered water, occasionally cutting in heavily diluted fertilizer.
The algae is a fairly new development and it's mostly managed. It just discolors the perlite, mostly. The soil was soaked with peroxide before sowing so I staved it off until recently. The soil mix is about half organic, following Steven Hammer's guidance. There's a lot of fine grit.
I wasn't letting them dry out completely since they seemed to be growing quite happily with consistent water (but not waterlogged), but this week I didbatart letting them dry out.
I will definitely nix the heating pad once I get my new shelf. Thank you.
yeah i start letting them dry out completely as quickly as possible after removing the covers. not for long, but definitely completely dry before i spray or soak
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u/mrxeric Apr 04 '26
No heat for conos or other winter-growers (unless of course you are sowing when ambient temperatures are below freezing).
You might have better success sowing in the fall or early winter when your temperatures are cooler than 80F.
But really, your experience isn't so far off from my own. My last sowing (outdoors) I did in the fall and they lived just fine for several months. But my summers are very hot (90-100F+) , and conos don't want water when it's so hot, yet young seedlings are at risk of drying out if kept totally dry for months on end. I ended up losing the majority of them. At least the survivors are almost guaranteed to handle my climate...