Last year I used a mostly mineral substrate that consisted of crushed pumice, decomposed granite, calcined clays, and some coco coir and pine bark fines. It worked well I think, but it was a bit laborious (and wasteful!) crushing the pumice and sifting the entire mixture to get a desired grain size. That, and it didn't make sense to me to use so much of the same material I use for my potted plants, for seedlings that will stay in that mixture for only a few months. Better to use it on my larger plants.
So after looking around a bit, I settled on using a modified substrate based on Aymeric de Barmon's method (see his method here). In that article he uses a mixture that is 1:1 vermiculite and blond peat. Since I already had the typical more decomposed peat, I used that instead. I decided to use less peat since it holds more water longer than vermiculite. My mixture was 4 parts vermiculite to 1 part peat.
Here's what it looks like, with an American penny for scale (3/4in or 19mm diameter).
I sterilized the mixture in the microwave, moistening it first to help create steam. Since I didn't have enough 2in(5cm) pots, I used mini 2oz. party cups (aka disposable shot glasses ). I poked some drain holes with a soldering iron and then I rinsed the "pots" well and sprayed with hydrogen peroxide before filling with the sterilized soil mixture. I then soaked the "pots" with a fertilizer "tea", made from soaking around a tablespoon of an organic fertilizer in roughly half a liter of warm water. I let the mixture sit for a couple of hours before straining out the solids. Last year I only used a mycorrhizae powder in the first few sets of seeds I sowed, but I started using this fertilizer on the rest of the seeds with good results. The fertilizer contains both mycorrhizae and other beneficial microbes. It does cause algae to grow though, which hasn't been much of an issue for me.
Before sowing the seeds, I let them soak in 50:50 mixture of 3% hydrogen peroxide and water for a few minutes. After sowing the seeds, I put the pots inside plastic sandwich bags and then put them all in my makeshift prop box, shown below.
The box is just a 106qt/100L plastic storage box, insulated with a layer of thin packing foam, a layer of aluminum foil over that, and some clear packing tape to hold it all together. The box is left inside the garage with no temperature regulation. I regulate the temperature inside the box by turning off the halogen lamp; usually not needed unless the garage is particularly warm on a given day. The halogen lamp is only used over the winter.
I then cover the pots with a "screen", which is just baking parchment paper stapled around a bamboo skewer frame.
I do this for 2 reasons: to diffuse the light and prevent the seedlings from going too red, and to prevent scorching from the direct heat of the halogen lamp directly above. Speaking of lamps, here's what those look like.
From left to right: a 2200 lumens 24W "warm" LED bulb, a 60W halogen floodlight lamp, and a 2200 lumens 24W "cool" LED bulb. There is no particular reason for using two different colors on the LEDs, just that those were what I had on hand. The three lamps raise the temperature at the bottom of the box to just above 90F/32C. I don't measure humidity.
I sowed the seeds in three groups in three consecutive days at the end of January.
- Mammillaria albiflora [ADBLPS 704]
- Mammillaria herrerae [ADBLPS 705]
- Mammillaria lasiacantha subs. egregia listed as Mammillaria egregia SB 30 Jimenez, Chihuahua, Mexico
- Cochemiea sheldonii 'marnieriana' listed as Mammillaria marnierana [ADBLPS 683]. Supposedly this a form of C. sheldonii without central spines, but some places list sheldonii as a subspecies of C. grahamii, while others claim C. sheldonii is synonymous with C. grahamii.
- Mammillaria napina [ADBLPS 11263]
- Mammillaria pectinifera [ADBLPS 895]
- Mammillaria pennispinosa ML 632 km17 of MEX-30 1350m, Bermejillo to Mapimi, Durango, Mexico
- Mammillaria dixanthocentron SB 527 Tecomavaca, Oaxaca, Mexico
- Cochemiea guelzowiana listed as Mammillaria guelzowiana SB 1160 Rodeo, Durango, Mexico
- Mammillaria perbella TL 556 w Zimapan (Tunnel?), Hidalgo, Mexico. The field number returns "Tunnel" as part of the location, but no such place exists?
- Mammillaria pottsii SB 102 Jimenez, Chihuahua, Mexico
- Mammillaria pottsii 'multicaulis' listed as Mammillaria pottsii v. multicaulis SB 1062 Lerdo, Durango, Mexico
- Mammillaria solisioides TL 377 Chila, Puebla (Oaxaca?), Mexico. The field number returns Chila, Oaxaca, but there is no Chila in Oaxaca?
- Mammillaria wagneriana L 1073 Penon Blanco, south of Nazas 1800m, Durango, Mexico
Here are a few pics of some of these at 3 months after sowing:
M. lasiacantha subs. egregia SB 30
M. pennispinosa ML 632
M. pennispinosa had the funkiest Mammillaria seeds I've ever seen.
Turns out this and C. guelzowiana (these had nearly indentical seeds) were once part of the old genus 'Phellosperma', named after that corky bit on the seeds. Maybe M. pennispinosa could also be reclassified as Cochemiea in the future?
M. solisioides TL 377
M. wagneriana L 1073
- Epithelantha bokei SB 416 Brewster County, Texas, USA. This is my second attempt!
- Homalocephala polycephala subs. xeranthemoides listed as Echinocactus xeranthemoides Meadview, Arizona, USA
- Pediocactus paradinei SB 502 Kaibab Plateau, Coconino County, Arizona, USA
- Pediocactus simpsonii RP 179 Pastora Peak, Arizona, USA
- Pediocactus simpsonii 'minor' listed as Pediocactus simposonii v. minor SB 199 Mesa County, Colorado, USA
- Sclerocactus nyensis SB 1456 Esmeralda County, Nevada, USA
- Sclerocactus spinosior subs. blainei 'schleseri' listed as Sclerocactus spinosior v. schleseri RP 136 east of Panaca 4900ft, Lincoln County, Nevada, USA
Here are pics of the three pots with germination, 1 or 3 months after sowing:
H. polycephala subs. xeranthemoides Meadview, AZ. This one is actually 1 month old.
P. simpsonii RP 179. A double-headed seedling!
S. spinosior subs. blainei 'schleseri' RP 136
- Cochemiea matehualensis listed as Neollydia matehualensis [ADBLPS 12022]. This taxon was not mentioned in the 2021 phylogeny study by Breslin et al., but I took the liberty of labeling it as Cochemiea.
- Echinocactus horizonthalonius 'subikii' listed as Echinocactus horizonthalonius v. subiki RS 615 Ejido Soledad, Nuevo Leon, Mexico.
- Parodia calvescens listed as Notocactus calvescens [ADBLPS 2404]
- Pelecyphora abdita listed as Escobaria abdita [ADBLPS 12020]. This 2022 phylogenetic study by Sánchez et al. proposes the reclassification of this taxon, but they didn't actually use it in the analysis. I've decided to keep the Pelecyphora name for now. The seed is black, very large and Pediocactus-like, unlike the tiny brown seed of the next Pelecyphora. Maybe the microstructure of each seed is similar?
- Pelecyphora strobiliformis [ADBLPS 1333]. My second attempt; ADBLPS seed for this is less expensive than last year's Mesa seed.
- Pterocactus australis RH 2312a (OR) Lago Viedma 400m, Lago Argentino, Santa Cruz, Argentina.
- Turbinicarpus alonsoi [ADBLPS 1752]
- Turbinicarpus saueri HO 900 Sierra Salamanca 950m, Tamaulipas, Mexico
- Astrophytum ornatum SB 127 Metztitlan, Hidalgo, Mexico
- Thelocactus rinconensis SB 301 Rinconada, Nuevo Leon, Mexico
- Thelocactus rinconensis subs. nidulans SB 1768 Sierra de la Paila, Coahuila, Mexico
- Turbinicarpus lophophoroides L 723 Las Tablas 1400m, San Luis Potosi, Mexico
Everything here had some germination except the Echinocactus, C. matehualensis, and P. australis (kinda...)
Here are a few pics from some of these:
A. ornatum SB 127
P. abdita, very etiolated
T. alonsoi featuring a double-headed seedling. Tiny Turbinicarpus seedlings from the the tiniest Turb seeds I've seen.
and mystery seedling from last years sowing. Looks Turbinicarpus-like. I may grow impatient and will graft it.
I did not record detailed germination data for this year's sowing. The main reason was that the seedlings kept dying soon after germination, as in the seedlings never made it beyond their radicle poking through the seed shell. The pots with "no" germination that I hinted at above succumbed to this. Here's an example, P. simpsonii 'minor' SB 199, there were 4 seeds that germinated and in the picture you can see two with the affliction:
that nasty red blob is the dead radicle. It was white a couple days before.
I'm not sure why this happened. Fungus? None of the affected pots had obvious fungal growth. Too hot or fertilizer burn? Maybe. Some pots with this issue, like P. abdita and H. xeranthemoides, had some successful germination and I would think temperature or soil condition would affect the healthy seeds too? Maybe I was just unlucky and got bunch of weak seeds? Who knows. It was frustrating that the pots with fewest seeds (and difficult to germinate) were the most affected (M. herrerae, P. abdita, P. australis, all with only 5 seeds each and the Pedio- and Sclerocactus).
I did not like this new substrate mixture I made. Although there were a few isolated cases of visible fungal growth (either webbing or fuzzy spores), their number were not significantly higher than what I observed last year with my mineral mix. What I did see was an increased number of dead seedlings on almost every pot. Most of them were from dead radicles, but a few just turned transparent and shriveled away. I will not discount invisible fungal attack encouraged by the peat in the soil.
Another issue with this mix is that it compacts when it dries. The pot with the mystery seedling was actually one of the few with visible fungus growth, so I took it out of the pot to dry, thinking the seedling would die. The seedling survived, but the soil sank down into the pot as it dried. Notice the line of crusted soil near the top of the cup. That was the soil level before drying.
I imagine this will disturb the roots and the compacted soil will just promote root rot later on. I decided to open all the bags to harden up the seedlings in preparation for pricking them out sometime soon. Last year I waited at least 6 months for most of the seedlings before pricking them out, but I think in this case sooner is better than later. In the future I will try adding perlite to stabilize the mixture and perhaps using a thin top layer of pumice or other mixture of pure mineral.
on something else
Not so much of an issue, but the habit Pedio- and Sclerocactus have when they germinate is frustrating.
They insist on not growing upright while leaving their roots to snake through the air above the soil. The few that I sowed last year showed the same habit. You can also see how they became so elongated that they even bent into a 'c' shape. This last thing probably has to do with poor light, which was apparent in many other seedlings from their etiolation (like P. abdita shown above). I have since moved all the seedlings closer to the light source and hopefully they'll recover from the etiolation.
on the end
Phew! This ended up being longer than originally planned. Hopefully I didn't bore anyone too much. The next update won't be for several months when I'll have something more than just nondescript green blobs with tiny spines to show. I hope, anyway.