Zac's Seedlings 2024

[zpeckler]

Hello everyone!

I'm gonna be sowing a ton of seeds this year... after I finish re-potting my seedlings from last year and am able to get them outside to free up space under my grow light. Before I did I wanted to put my plan out there and see if anyone had any comments or advice. I don't want to mess up with some of the difficult species I have planned.

I was going to sow the seeds in a substrate that's 25% mature compost, screened to remove pieces larger than 1/8". The compost comes from a local source and is derived from wood/bark chips, lawn clippings, etc. I talked things over with the owner of the "worm farm" and the compost is aged between 6-12 months prior to it going on sale, and no animal products or meat food waste goes into it. I was going to follow advice given to me by MikeInOz and use the compost as-is without sterilizing it in order to have living mycorrhizal fungi and other beneficial microorganisms.

The remaining 75% of the substrate will be a 50/50 mix of small pumice and scoria between 1/12-1/8".

I have decomposed granite that I screened to also be between 1/12-1/8" that I was going to use as top dressing. I could also mix that into the substrate if people think that would help?

If the particle size of the minerals are too small, I can screen for larger if needed. I want the mix to be well-draining, but also able to retain enough water for seedlings without things getting saturated and soppy.

I was going to sow the seeds in 3.25" nursery pots in 1020 trays under a humidity dome. I have LED grow lights with a dimmer to dial in brightness. Heat mats, of course.

Here's a list of all the seeds I have to sow. Yes, I know I'm going totally overboard. Totally, totally overboard. What can I say, the bug just bit me this year! No, I have no idea what I'm going to do with all these seedlings. Give away the extras, I guess.

Peckler-Seedling-List.jpg (182.15 KiB) Viewed 3254 times

In particular I'm concerned about whether my substrate is appropriate for the Copiapoas, considering I've never sown anything from South America before. I'm also concerned about the more difficult, rot-prone species I'm trying such as Echinocactus polycephalus, the Echinomastus species, and Escobaria alversonii. Would any modifications to my substrate be more appropriate for them? I have a ton of E. poly seeds, so I could even try multiple substrates.

[Nino_G]

I had terrible results with organic substrates for sowing. In almost all cases I had detrimental fungal infection sooner or later in the seedling pots. Probably I made a mistake by sterilizing substrate before sowing and therefore killing beneficial microorganisms. Anyway, for a long time now I've been using mineral substrates exclusively with good results. My substrate of choice is mixture of about 50% pumice, 20% zeolith and 30% akadama. All ingredients are sieved to 1-3mm grade. For very small seeds (e.g. Strombocactus, Aztekium, etc.) it is advisable to add thin layer of fine pumice sand on top of it to prevent seeds from dropping too deep into the substrate and to give the tiny roots something to hold on to. Substrate is sterilized, as well as water and pots prior to sowing. Also I treat most seeds with bleach solution (50% household bleach and 50% water) for 20 minutes and then thoroughly rinsed with clean water. Some growers also treat the substrate with a fungicide as the additional precaution. If you plan to retain the seedlings in sowing pots for a long time without opening the lids/bags it is advisable to add fertilizer to your water. Weak solution (1/5 of recommended dosage) is adequate.
I wish you the best of luck.

[MrXeric]

If you are not sterilizing your organic component, be sure to periodically check for visible fungus or damping off of seedlings and begin drying out the pots if you spot something amiss.

I think the particle size you posted is appropriate for seedlings. I use something of similar size with good results.

I've found that Copipoa aren't too picky about substrate (from your list I've sown C. atacamensis and C. calderana), just that I find them reluctant to germinate. I probably keep the pots warmer than I should.

I had terrible results with organic substrates for sowing. In almost all cases I had detrimental fungal infection sooner or later in the seedling pots. Probably I made a mistake by sterilizing substrate before sowing and therefore killing beneficial microorganisms. Anyway, for a long time now I've been using mineral substrates exclusively with good results. My substrate of choice is mixture of about 50% pumice, 20% zeolith and 30% akadama. All ingredients are sieved to 1-3mm grade. For very small seeds (e.g. Strombocactus, Aztekium, etc.) it is advisable to add thin layer of fine pumice sand on top of it to prevent seeds from dropping too deep into the substrate and to give the tiny roots something to hold on to. Substrate is sterilized, as well as water and pots prior to sowing. Also I treat most seeds with bleach solution (50% household bleach and 50% water) for 20 minutes and then thoroughly rinsed with clean water. Some growers also treat the substrate with a fungicide as the additional precaution. If you plan to retain the seedlings in sowing pots for a long time without opening the lids/bags it is advisable to add fertilizer to your water. Weak solution (1/5 of recommended dosage) is adequate.
I wish you the best of luck.

Also, very good advice here!

[keith]

I had terrible results with organic substrates for sowing." Agree i don't use any at all . I use small sized Pumice mixed with sandy soil and spray the seeds with hydrogen peroxide then rinse with water before sowing. I also add diatomaceous earth powder to discourage insect pests.

[zpeckler]

Thanks for the replies, everyone! I had posted a similar topic regarding mineral mixes for seedlings several months ago.

Here on the forms and elsewhere it seems like maybe a majority of people have some soil component in their seedling mixes, but I've gotta admit that I am coming into this with a pre-conceived bias towards all-mineral mixes based on my experience with some difficult species doing badly in--admittedly poorly-conceived on my part--mostly organic substrate.

I'm definitely leaning towards an all-mineral substrate based on the advice received here, considering I'm gonna be growing more hard species like Echinomastus, Echinocactus polycephalus/xeranthemoides, and Escobaria alveraonii. I'm guessing a mix of pumice, scoria, decomposed granite, and akadama would be in order? Maybe pumice, scoria, and akadama in the mix with DG top dressing?

I've never used akadama before, but it's my understanding that I should be looking for the "hard" variety? What do you think about the following product:
Japanese Super Hard Akadama - Shohin Grain ( 2 mm - 3 mm )

From what I understand akadama also has a moderate CEC? Maybe enough that fertilizing every other watering would be enough?

[Nino_G]

I'm guessing a mix of pumice, scoria, decomposed granite, and akadama would be in order? Maybe pumice, scoria, and akadama in the mix with DG top dressing?

I have no experience with DG (it's not available in my area), but I read that people use it in mixtures with good results (e.g. Steve Johnson of this Forum is reportedly using mixture of pumice and DG for his plants). Otherwise, your mix sounds good to me.

I've never used akadama before, but it's my understanding that I should be looking for the "hard" variety? What do you think about the following product:
Japanese Super Hard Akadama - Shohin Grain ( 2 mm - 3 mm )

From what I understand akadama also has a moderate CEC? Maybe enough that fertilizing every other watering would be enough?

Yes it's advisable to use hard akadama because it will decompose much more slowly (i have some in pots for three years now, and it still looks good).
Akadama in your link is good, but it looks extremely expensive to me. I can buy 17l (18 quart) bag of 2,5-3mm grade for aproximately 20$ here, so do a bit of a research (perhaps you may consult bonsai growers in your area).
Akadama has decent CEC, and zeolith has very high CEC. That's exactly why I like to add them to inorganic mixtures.

[zpeckler]

Well, I was able to sow my seeds about a week ago. Been busy with a ton of work so haven't been able to make an update until now.

I ended up going with a mix of equal parts pumice, scoria, and akadama, with fine DG top dressing so the smaller seeds don't fall too deep into the substrate.

Seedling-Substrate.jpg (206.37 KiB) Viewed 2939 times

I sterilized it by baking in the oven for an hour at 450F, then used C&D's Physan 20 and chinosol protocol prior to sowing. I'm hoping the soapy action of the Physan helps up the germination rate.

All the seeds were sown in 3.25" pots in 1020 trays, covered with humidity domes and set on seedling heat mats under Spider Farmer LED grow lights. It's kinda tough to see through the domes, but I'm pretty sure I've got some specs of green popping up!

[zpeckler]

....and the other shoe has dropped. It's tough to see completely through the humidity dome, but I can definitely see what looks like a fine white "spider web" covering the surface of one of my pots right at the edge of a tray. Definitely some kind of fungus or mold. Ugh, it's literally only been a week since I sowed the seeds! So frustrating! I thought sterilization plus spraying with two different fungicides would make this unlikely, and am pretty dismayed that I'm seeing something so bad so quickly.

I can only see it in one pot, but visibility of most of the interior of the trays is extremely limited. I'll try and get a pic, but had to run off to work right after noticing it.

Any advice on where to go from here? Materials on hand are Physan 20, chinosol, 3% hydrogen peroxide, sulfur powder, and a copper fungicide I use on my peach tree.

Thanks in advance.

[zpeckler]

I managed to peek through one of the vent holes on the humidity dome, zoom way in with my phone, and take a pic. The white webbing is completely covering the surface of one of my pots where I sowed some Copiapoa, and two of the neighboring pots have some areas where the webbing is developing on the surface. Definitely some kind of mold or fungus.

Seedling-Disease.jpg (102.08 KiB) Viewed 2842 times

Anyone have any suggestions for how to combat this? I'm thinking of opening the dome and taking the afflicted pots out to quarantine in ziploc baggies, but I worry that the damage is probably already done and the entire tray is inoculated.

[Nino_G]

Incredible. Considering all the precautions you have taken, I don't understand how it's possible for mold to proliferate to such extent in such short time. Have you sterilized the pots/tray/dome? You can try spraying with more fungicide, although I don't have any experience in using those. If seeds haven't germinated yet, it's best to expose them to fresh air and let them dry somewhat. You can also try spraying with hydrogen peroxide (H2O2), but it's efficiency is limited - some types of molds are killed instantly, while some other may have no reaction at all.

[keith]

your pots look too wet. Take the pots out and expose to sunlight and breezes and under screen to protect from full sun. The seedlings will slow down but should survive .

The whole baggie thing I stopped keeping cactus in them for more than a few days years ago . Acually growing cactus now and had fungus, always do , and got them outside under sunlight with two pieces of window screen over the plastic lid . M schumanii, M lenta, E bokei, M meicantha, E robbinsonii, T polaski ,T lohoporides , M humboltii . They germinate over many weeks and I spray with a fine mist of water daily if its sunny. Some started to rot when the weather was cold in March ( inside on a heat mat and not enough sunlight ) so I probably should have waited another month. I have no idea if grow lights kill fungus like sunlight does ? I have a video where I show my method of sowing cactus seeds. My method they grow very slow compared to baggie method so if you're in a hurry .... And I use real soil from the desert mixed with pumice and sand I don't know if that makes a difference as far as fungus goes ?

[zpeckler]

Nino and Keith, thanks to both of you for your thoughts and consolation.

The fungus/mold is now in all three of my trays. Only a few pots are as dramatically covered as in my picture, but the majority have visible "webbing" to one degree or another. There's no consistent pattern in what pots are infected--all different species, seed source, and location in the trays. I'm definitely getting germination, with multiple 1-2mm seedlings in a bunch of my pots, including a bunch that are sprouting in the infected pots.

Incredible. Considering all the precautions you have taken, I don't understand how it's possible for mold to proliferate to such extent in such short time. Have you sterilized the pots/tray/dome? You can try spraying with more fungicide, although I don't have any experience in using those. If seeds haven't germinated yet, it's best to expose them to fresh air and let them dry somewhat. You can also try spraying with hydrogen peroxide (H2O2), but it's efficiency is limited - some types of molds are killed instantly, while some other may have no reaction at all.

Yeah, I sprayed the trays, lids, and pots with Physan 20.

I tried spraying a test pot (where seeds hadn't germinated yet) with hydrogen proxide and it had no effect. I also tried the copper fungicide I have and things look a little better after one day but there is still a lot of fungus/mold, so that's probably not gonna be effective either.

your pots look too wet. Take the pots out and expose to sunlight and breezes and under screen to protect from full sun. The seedlings will slow down but should survive .

The whole baggie thing I stopped keeping cactus in them for more than a few days years ago . Acually growing cactus now and had fungus, always do , and got them outside under sunlight with two pieces of window screen over the plastic lid . M schumanii, M lenta, E bokei, M meicantha, E robbinsonii, T polaski ,T lohoporides , M humboltii . They germinate over many weeks and I spray with a fine mist of water daily if its sunny. Some started to rot when the weather was cold in March ( inside on a heat mat and not enough sunlight ) so I probably should have waited another month. I have no idea if grow lights kill fungus like sunlight does ? I have a video where I show my method of sowing cactus seeds. My method they grow very slow compared to baggie method so if you're in a hurry .... And I use real soil from the desert mixed with pumice and sand I don't know if that makes a difference as far as fungus goes ?

You're Cactus Duty on Youtube, right? I'm already a subscriber! Your videos are great, very informative. Making them with your kids must be really fun!

Since fungicides are clearly not going to help I'm going to try drying them out. You're right, Keith, the pots are pretty sopping. I don't care if they grow slow, I'm in no hurry and would rather have good plants than big plants quickly.

I got three new 1020 trays and humidity domes. I washed them all with soap and water, and then sprayed them thoroughly with StarSan, a phosphoric acid and emulsion product commonly used in homebrewing to sterilize equipment prior to brewing. I let the trays and domes dry off before moving all the pots from the old domes to the sanitized ones. I don't know if re-sterilizing things is necessary considering the cat is clearly out of the bag at this point, but oh well. I put the trays out in the sun with the domes on, but all the vents fully open. I don't have anything else on hand that's clear and big enough to cover the trays to keep critters or other debris from getting in the trays. I then covered the domes with 30% shade cloth doubled over to make two layers.

I see a few things that could be wrong with this set-up, and am definitely open to suggestions on how to do better.

Firstly, the humidity domes won't allow a lot of breeze and airflow.

Secondly I'm definitely gonna have to re-mist the pots every day to keep the seedlings form dessicating and dying. I guess there's no way around that considering I'm intentionally trying to keep things dryer.

Lastly--and this is the one I'm concerned about--I worry about how hot it's going to get under the domes. Daytime temps are in the mid-to-upper 70's lately (77F and partly cloudy right now), and I'm concerned that it could get hot enough to be lethal to the little seedlings. I'm keeping an eye on things with a BBQ temp probe suspended in the air over the surface of the pots, kinda like if you were checking a "pit temp", and so far the air temp under the dome is over 108F! Is this gonna be a problem?

[keith]

108F is too hot you'll need to add ventilation or move to a shadier location . If the seedlings turn Red and stop growing its too much light .

Sulfur will probably work better than that other stuff .

[zpeckler]

108F is too hot you'll need to add ventilation or move to a shadier location . If the seedlings turn Red and stop growing its too much light .

Sulfur will probably work better than that other stuff .

That's what I thought. I'll up the shade cloth percentage and keep an eye on things. What would you consider a maximum temp to keep things under?

Just to be clear, I only sprayed the StarSan on the 1020 trays and domes, NOT on the pots, substrate, or seedlings. I'm pretty sure it would be really detrimental to the seedlings, but works great for surface sterilization of equipment.

[keith]

80-90F day time and 60 -70F at night . I try and keep the very top of the soil dry and sticky sand grains wet to a tweezers or stick or whatever you use to test the soil 10-20 mils down under the surface. Once you get that dry - wet balance you could put the whole thing in a baggie, many do, but I always get fungus eventually doing that . I put them under a plastic dome instead which is kinda like a baggie but easier to lift off to inspect for problems. Eventually , maybe 3 months , they go under screens each pot with a screen tied on with a rubber band and then under a 50% sand cloth box . I use 3% hydrogen peroxide once in a while to water other times filtered water . They germinate over many weeks sometimes months. If I get damping off fungus the pot is often doomed but if I catch it quick enough I use a root tone powder with fungicide and expose to dry air and filtered sunlight unless the weather is cloudy which can be a problem.