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The substrate looks too wet, that'll create problems for growing beyond germination. With the right moisture level and sanitation, there should be no algae or moss. It should be moist but not wet. Ideally it will dry out slightly on a daily basis due to the heat from the lights pushing moisture around, as well as condensation. If it looks dry-ish at the surface when the lights have been on a while, but moist when they're off, it's perfect. That's easier to accomplish in a larger pot and reduces damping off greatly. Seedlings in nature mostly live on condensation and moisture that wicks up at night that they get daily in the growing season, and this mimics that.
I've used the 'disposable shot glasses' with decent results before, but rather than poke drainage holes I plop in the properly moistened media, sow and snap the lid on. Then they stay sterile and at the perfect moisture level indefinitely. Taller ones (IE 4oz) with clear lids allow you to keep track of progress without breaking quarantine, but translucent ones also work fine, you just can't see inside. These days I use 3.25" pots in 6" wide x 12" tall ziplock bags, that eliminates needing to repot for several years. They can also stay in the bag for up to 5+ years (strombocactus, aztekium, blossfeldia). They are zero work that way, and since you aren't adding water the soil doesn't get salty to require new soil. Little guys will never use up the available nutrients, and they don't get disturbed by watering.

promethean_spark wrote: ↑Wed May 25, 2022 6:19 pm The substrate looks too wet, that'll create problems for growing beyond germination. With the right moisture level and sanitation, there should be no algae or moss. It should be moist but not wet. Ideally it will dry out slightly on a daily basis due to the heat from the lights pushing moisture around, as well as condensation. If it looks dry-ish at the surface when the lights have been on a while, but moist when they're off, it's perfect. That's easier to accomplish in a larger pot and reduces damping off greatly. Seedlings in nature mostly live on condensation and moisture that wicks up at night that they get daily in the growing season, and this mimics that.
I've used the 'disposable shot glasses' with decent results before, but rather than poke drainage holes I plop in the properly moistened media, sow and snap the lid on. Then they stay sterile and at the perfect moisture level indefinitely. Taller ones (IE 4oz) with clear lids allow you to keep track of progress without breaking quarantine, but translucent ones also work fine, you just can't see inside. These days I use 3.25" pots in 6" wide x 12" tall ziplock bags, that eliminates needing to repot for several years. They can also stay in the bag for up to 5+ years (strombocactus, aztekium, blossfeldia). They are zero work that way, and since you aren't adding water the soil doesn't get salty to require new soil. Little guys will never use up the available nutrients, and they don't get disturbed by watering.

Thanks for the feedback. I actually have noticed the substrate surface drying before. I assumed I didn't provide enough moisture so I opened those bags and sprayed the pots. I did not think to check if there was any condensation going on on the surface before turning on the lights/heat. I will keep this in mind for future sowing.

It's been about 2-3 months since I've transplanted these seedlings out of the bad substrate and now I am ready to post an update. I potted the seedlings in the mineral based mix I use for most of my plants: pumice, decomposed granite, red lava rock (scoria), Bonsai Jack's Succulent Soil (calcined clays with added pine coir), and a small amount of sifted peat and worm castings, roughly 85/15 mineral to organics.



for the smaller seedlings I used a similar mix, but smaller in grain size and with less added organics. I use it for rooting cuttings and for some mesembs. This is also very similar to the mix I used for last year's sowing. Most of the pumice I crushed using a hammer, which was a nuisance and part of the reason I didn't use this mix for this year's sowing.



Most seedlings survived the ordeal despite having underdeveloped roots, being only a few months old, but some did complain.

Here are the Mammillaria (and Cochemiea!) at just under 7 months old:

Cochemiea guelzowiana SB 1160. Yellow and red hooks!


Cochemiea sheldonii 'marnieriana'.


Mammillaria albiflora.


Mammillaria dixanthocentron SB 527. These didn't like the transplant. Nearly all of them died within days of potting. Didn't think these would be so sensitive!

Before transplanting:


the only survivor...I should've just let these be!


Mammillaria lasiacantha subsp. egregia SB 30.


Mammillaria napina.


Mammillaria pectinifera.


Mammillaria pennispinosa ML 632. Fuzzy centrals!


Mammillaria perbella TL 556.


Mammillaria pottsii SB 102.


Mammillaria pottsii 'multicaulis' SB 1062. These also complained; I lost about half of them!


Mammillaria solisioides TL 377. Some of them had their growing points damaged by I don't know what, but they seemed to have recovered.


Mammillaria wagneriana L 1073.

rare cactus seedlings they look pretty good to me . I grow seedlings outside so its different, more misting no plastic after the first few weeks .

Cochemiea guelzowiana SB 1160 is that what they call it now not mammillaria ? Dry stall pumice is smaller don't have to crush it .

keith wrote: ↑Sun Aug 21, 2022 2:44 am rare cactus seedlings they look pretty good to me . I grow seedlings outside so its different, more misting no plastic after the first few weeks .

Cochemiea guelzowiana SB 1160 is that what they call it now not mammillaria ? Dry stall pumice is smaller don't have to crush it .

Thanks keith. I've tried looking for dry stall at my local feed stores, but they don't carry it.

Whenever possible, I try to name my plants according to the current science. A couple dozen former species of Mammillaria, including M. guelzowiana, were found to be more closely related to Cochemiea than Mammillaria in the strict sense.

I forgot to mention in the last post that I kept the seedlings out of the bag after transplanting. Also, of the Mammilloids, Cochemiea matehualensis never germinated and Mammillaria herrerae had one seed germinate that died soon after, but nothing else germinate after drying and rehydrating over the last few months.

Anyway, here is an update on the American species I sowed, shown at nearly 7 months old.

Epithelantha bokei SB 416 Brewster County, Texas, USA.


Homalocephala polycephala subsp. xeranthemoides Meadview, Arizona, USA.


Pediocactus simpsonii RP 179 Pastora Peak, Arizona, USA.


Sclerocactus spinosior subsp. blainei 'schlesseri' RP 136 Lincoln County, Nevada, USA.


The following did not germinate:

Pediocactus paradinei SB 502

Pediocactus simpsonii 'minor' SB 199 - some germination early on, but they died soon after

Sclerocactus nyensis SB 1456

MrXeric wrote: ↑Mon Aug 22, 2022 1:57 am Dry stall pumice is smaller don't have to crush it .

Thanks Keith. I've tried looking for dry stall at my local feed stores, but they don't carry it. [/quote]

I tried out here in the east and could not find Dry Stall here either. Searches come up with Stall Dry, which is clay and Diatomaceous Earth based. Not the same as Pumice. I bought the Dry Stall at a Connecticut Cactus and Succulent Society show years ago. I tried getting more last year.

Theresa's Country Feed & Pet have any of those around ? Maybe not back east though ? Pumice is a western USA product might not make it back east ?

I did see pumice being offered on Amazon in a search. Didn't order any though.

keith wrote: ↑Mon Aug 22, 2022 5:59 pm Theresa's Country Feed & Pet

The nearest one in Simi Valley is 75 miles away - likely a two hour drive, one way, depending on the time. No thanks!

Here's the 7 month update on the remaining seedlings, mostly Mexican species.

Astrophytum ornatum SB 127.


Parodia calvescens. These are actually 3 months old. The seeds were originally sowed in January with the rest, but only 1 seed germinated in this pot (it died). I extracted the remaining seeds, washed and dried them, and sowed them again in May.


Pelecyphora abdita (=Escobaria abdita).


Pelecyphora strobiliformis.


Thelocactus rinconensis SB 301.


Thelocactus rinconensis subsp. nidulans SB 1768.


Turbinicarpus alonsoi. Tiny.


Turbinicarpus lophophoroides L 723. The only survivor of 5 seeds that germinated.


Turbinicarpus saueri HO 900.


The following did not germinate:

Echinocactus horizonthalonius 'subikii' RS 615

Pterocactus australis RH 2312a - 4 of 5 seeds germinated periodically (I dried and watered several times), but the root died without the cotyledons breaking through the seed. I'm starting to think these don't like heat when germinating.

looking nice... all your cacti are growing slowly but they are much hardier.

Looking at your pictures I'm glad I sowed very heavily Turbinicarpus rather than using 2 planters used only 1... they should be fine for a year or longer.

LateBloomer wrote: ↑Sun Aug 28, 2022 8:03 pm looking nice... all your cacti are growing slowly but they are much hardier.

Looking at your pictures I'm glad I sowed very heavily Turbinicarpus rather than using 2 planters used only 1... they should be fine for a year or longer.

Thanks! I expect to keep most of these in the same pots for a couple years at least, which is good because I am running out of shelf space!

I sowed a bunch of seeds from my own plants in 2022, mostly stuff I've shown before, but here are some new ones.

hybrid Turbinicarpus pseudopectinatus x valdezianus, 8 months old.


I was surprised to find a fruit on my Mammillaria senilis since I only have the one plant. It was visited by hummingbirds while it was blooming so I am wondering if it was pollinated by something compatible nearby or if it self pollinated. Only 9 seeds were in the fruit and not all of those germinated, so I suspect selfing. Anyway, these seedlings are 5 months old.


These are also 5 months old, Mammillaria stella-de-tacubaya.


I also sowed several Astrophytum, mostly hybrids because I didn't want to store pollen, but I caught a couple Astrophytum myriostigma in flower at the same time. These seedlings are 3 months. Probably getting more light than they would like.


I am pretty excited about these Cochemiea theresae, also 3 months old. I pollinated one of my plants with 1 year old frozen pollen from another that didn't bloom and that resulted in two fruits. These seeds came from one fruit that I harvested a few months after blooming. I kept the seeds dry at room temperature before sowing a month later. 10 of 13 seeds germinated within 2 weeks with no special treatment, though the surface soil did dry from not closing the baggie correctly so I rehydrated the seeds with a water and peroxide solution. The second fruit I will harvest later this year to test if those seeds will germinate just as readily as these.


Also 3 months old, Bulbine mesembryanthoides (subsp/var mesembryanthoides). I started these outdoors in the fall with fair results. The smaller seedlings dried out after opening the bag so I added a thin layer of sand to keep the surviving ones from drying out too.

Eric, question on pollinating: I am assuming you are using a paintbrush to transfer pollen-correct?

If a brush: do you clean it between uses to prevent unintentional hybrids? How do you clean it? How long does it take to dry?