mixes and probiotics for seedlings?

I’m trying to figure out better seedling mixtures for my plants. I know I need to up my fertilizer game as I look at other’s really robust seedlings, and compare them to my comparably stunted plants. Unfortunately, I’m not entirely sure what I have recently been doing so poorly.
My track record would indicated that when I use organic stuff lately, my seeds damp off or otherwise are attacked. (In the past, old potting soil, heavily amended and left in the elements, seemed to work surprisingly well.)
I can’t help but think that the proper probiotics (as per some recent research) should be beneficial, but clearly anything organic needs to be very well decayed to not harbor pathogens that might attack vegetation.
I’m wondering what others use for seedling mixes, as well as for fertilizers, for their very young seedlings, and if anybody has don’t much research on “plant probiotics.”

I have used Miracle Gro Moisture Control Potting Soil (NOT the white bag “organic” made from “landfill” garbage! That stuff is NASTY!) for easily the past decade-plus. I do fertilize the planted seeds with a weak calcium nitrate solution (teaspoon per gallon?) and once they are up and growing, IF I fertilize, it’s with Miracle Gro All Purpose from the hose end sprayer. I raise them outside and don’t refrigerate.

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I have tried many different ways, and the way I settled on was both beneficial and cheaper.

Two to three parts basic garden mix soil w/out fertilizer, wetting agents, rocks, or large materials. One part cow manure compost that is left over from the prior year. The older the better. Mix these well.

Cow manure has a lower burn rate than other animal composts. It is quite cheap. It degrades slowly enough to not need fertilizer use in the first year. Most importantly, it suppresses various soil born pathogens known to damage seedlings. I tested it versus Captan one year, despite my judgment allowed a known carcinogen near my home. Of course, all PPE precautions were taken. The cow manure compost mixed in at a reduced ratio was superior.

For large scale, this has been cheap and effective. I would strongly suggest staying away from (peat; coconut) fiber materials for seedling beds. It can create an environment that aids root gall nodules on delicate seedling roots.


I had a seedling that grew well and suddenly stopped. After replanting I noticed a relatively large bulb on the root (about the size of a small pea). I didn’t know what it was, but now I’ve read this I guess it would be such a root gall nodule? I tore it off and replanted the seedling in a pot for the winter. Maybe it will recover after not growing for a whole summer.

I did have a lot of damp off this year on my Rugosa crossings last spring and I think I used peat in my soil. I’ll skip that. Never use it again for seedlings. Thanks for the tip.

@philip_la I’ll try using a solution of EM on my seeds just before sowing. I’ve explained some on another topic this week. septic way sowing - #17 by Roseus Maybe it could give some insight.

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Wow. I’m insanely slow to revisit your posts! Thank you, and very timely for me.

I think that Miracle Grow leans heavily to peat, and historically peat blends are what I used most successfully in the past. Peat purportedly has some antiseptic qualities that presumably help against damping off. Admittedly, my failed seedlings were in an “organic” mix, as I tried to go more organic in my feeding regime. Again, my thoughts were that “probiotics” might help, but my mixes should probably have been allowed to compost longer…

I may use my too-many OP Carefree Beauty seeds to conduct some experiments this year, but in the meantime, play it safe for my “more valuable” crosses – i.e. the ones that will likely end up in the compost pile most quickly.

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I’ve used peat also, because it would have antiseptic qualities. But now I’m pretty sure it is peat moss that has those qualities. That would be the medium to choose to stratify your seeds in.

Last year, I conducted a small, but controlled experiment that included straight peat moss, as well as pH balanced peat (a Fertilome mix). While the straight peat was indeed antiseptic, I had much better success with the commercial mix, and is what I am using exclusively for my 2022 crosses.

Your insertion of using a commercial mix is very interesting because I had last year the same observations.

Here is my germination medium recipe composed as follows:

60% commercial mix, 10% worm castings, 10% additional perlite, 10% vermiculite, 10% fine, cleaned quartz sand, all components well mixed and slightly diluted with distilled water.

I did not use calcium nitrate so far. I only use hydrogen peroxide in case of mold formation, which hardly ever happens.


Same as you, I observed that first germinations took place 10 days after stratification and putting the seeds into this mix. Furthermore, the majority of seed germinations occured between the first 4 weeks too. I’m convinced that a commercial mix works very well.

Over all, it’s funny that we had the same idea.