Seed starting mixtures


I used to use Promix for my fruit tree nursery and it worked fine, but I half buried the pots and let the roots grow out. I do prefer a heavier mix now with sand and compost for my nursery mix.

I only use the promix for starting vegies and growing a couple of large tomatoes. Most of those are in the ground, however.


I wanted to post a discovery this year, so looks like I’m going to revive this old topic. I’m doing some air layers this year and Scott on Ourfigs suggested using Black Magic potting soil. Home Depot has it. I think it really is black magic! I was out of seed starting mix and this potting soil is coir and perlite, with some fertilizer too (I think?)
Anyway I decided to try it for seed starting. it’s sterile, and cheaper than regular seed starting and no fungus gnats in coir. Holy Moly! This stuff works well, better than anything I ever used. My peppers and tomatoes came up from seed in record time.
I planted some Zinnia seeds and 2 days the were 1/2 inch tall! What?! I planted some Echinacea seeds which take 10-20 days to germinate. In 4 days they came up! Shut the door! Huh!?? I never seen anything like it. A little hard to figure out coir. Looks easy to get too wet, my only complaint. Holds water well. I think the even balance of water in this stuff is why it works well. I’ll be using this stuff from now on. Not all the Echinacea came up yet, but two did come up at 4 days and that is very impressive.


Wow, I see it says 2 years later above my last post, man time is just whipping by! All the Echinacea seeds were up this morning, Five or 6 days have only passed. When on the internet I saw 10-20 days. The seed packet says 14-21 days. I only used 6 seeds, as I’m adding about 10 different flowers to the garden.


Since it’s another dank, rainy day (shocker), I’m starting my veggies today. Got a couple 72 pod hex starter trays, and am trying a different mix this year. The last couple years, I’ve used the Jiffy pods, just add water, fluff it up, add seeds, and onto the heat pad. I’ve had decent germination with this method, but had a few peppers not come up, as well as some herbs and 'mater’s.

Did some reading about pepper seeds not really liking peat, which is the predominant material in these Jiffy pods. Maybe it’s the low pH of the peat that inhibits germination. So, going with a different mix this year, it’s MG Organic Choice potting mix. It has mostly composted forest products, and some moss, but not very much.

But, that Black Magic sounds like some good stuff, I’ll have to look into that. I wonder if Lowe’s has it, we don’t have a Home Depot within 50mi of us.


I’m not sure why it went so well? I was using old seed too. All the flower seed I used was 2 years old, some of the tomato and pepper seed was from 2012. I put in 2-3 seeds in some cells, and all germinated. I never thinned like this before. A couple peppers, and a couple tomatoes failed to germinate, but it was old or even moldy seed. I had that accident where my seeds got wet.
I also used the Black Magic in the first up pot. From here they go in ground, or containers.
Black Magic also makes a peat based mix, it is really expensive though. I bought the coir mix for air layers, but decided to use it for my seedlings too. It has a ton of big perlite in it.
Here are three of the peppers I up-potted today… In the BM soil. I have 19 plants this year.


IMO, the soil mix has nothing to do with the germination rate of the seed if it doesn’t rot the seed. It is soil temperature and quality and species of seed. Take some of your standard mix, get it to similar moisture level as your “magic” mix, packed to the same density (for equal heat transferrel), place a few seeds in two identical containers, with the contrasting mixes placed side by side and record your results. Then maybe any full throated endorsement you make will fall under the category of useful guidance, although I will still be skeptical until I’ve tried the experiment myself.

Once the seed has emerged and begins to develop a root system the mix becomes important- usually the lighter mixes are better and many potting mixes sold at stores are not Pro-mix (“peat-light”) type formulations and too heavy to be ideal for starting seeds.


I’m not sure what it is, as it doesn’t really seem that different than anything else? I may finally be getting better at it. One observation, and for me might have made the difference is the even distribution of water, and the ability to keep soil structure without getting soupy. With coir when you over water the stuff appears to breath. I got my tomato seeds way too wet, just by the weight of the tray. Doing it for so long, one literally has a feel for it. It took forever to dry even under warm lights. Yet the seeds didn’t rot. So the mix can “buffer” your mistakes. It doesn’t dry out as bad, and you have to work at drying it out. If you use coir, how it absorbs and holds water is deceptive. Be careful not to over water as it’s hard to tell when it is ideal. Although appears more forgiving when you do. It’s not just the coir, this mix is super heavy in perlite. So the combination, the pieces are chunky, not super small as in Promix. I use Promix (instead of peat) in my homemade soil mix for containers. I think I’m switching to Black Magic Coco Coir Mix.


I can see how better drainage might help them grow better after germination, but the energy for germination comes entirely from the seed. You were praising the mix for how quickly things germinated.

I was using the term Pro-mix generically- there are several quite similar mixes. I can’t remember the name of what I’m using now but I bought it from a commercial green-house grower and it is what he uses because Pro-mix costs considerably more. 3 cubic foot tightly compressed bails. Not available at Home Depot.


It’s sold at Menards the general purpose. They make a few different Pro-Mix mixes. , same company that produces all the peat from Canada. Maybe you’re referring to something different? Most users on other forums are referring to what I’m talking about when they use the term Pro-mix, as that is the name of the product. Huge compressed bales. I still like Black Magic better, but it is more expensive, it ain’t cheap. I resisted coir, tried it two years ago. I was not impressed, but I am now. I just like the mix, to each his own. It performed better as a seed mix than anything else I have used in 6 years. Now I know if the seeds don’t come up it’s bad seeds, not me… It appears next to impossible to mess it up with this stuff, even when you over water. In peat the seeds would have rotted. It stays wet longer too, so the seeds tend to germinate before they dry out. It’s worth trying. Also when it does dry it is not hydrophobic. Wets easily. Often a peat mix that drys stays dry under the roots and the plant dies. I heard this many times on garden shows. Never happened to me, but my mixes are not mostly peat, they are mostly pine bark.


Commercial mixes all add a wetting agent, it is untreated peat moss that resists wetting. Once in the soil, all quick draining potting mixes tend to dry out because their texture is coarser relative to real soil. It has no capillary pull to help bring water from much finer, real soil. Usually plants quickly grow into the real soil so it doesn’t become an issue, but it is suggested when planting from pots that you not cover the potting soil with real soil until the plant is established in the new soil so you can water the potting mix directly. Water does tend to run around potting soil when it is completely covered with real soil.

Small commercial farms often start plants in blocks of real soil to avoid this problem.


I do many seedlings for our cut flower sales and I too used coir this year for the first time to start the seeds. And I agree with you Holy Moly was my response too. I am not sure the germination was affected but the seedlings did way better in the coir, no fungus gnats, no damping off, none of the usual things that go wrong when you do hundreds of seedlings. I am going to stock up on some this summer, finding it in Feb. when my seeding schedule starts is nigh impossible here.


Yes, I didn’t even mention that! Coir rocks man!
I agree I don’t think germination was affected either, just less things can go wrong, so yield increases. Experienced users know how to keep a mix moist, and whatever else you need, heat etc. So experienced users will get good germination in broken glass, But the mix makes it so easy. Buying compressed coir would be a way to keep the price down instead of a pre-made mix. I don’t need a lot, one bag of Black Magic was enough, and I’m willing to pay for not making my own. Making my own potting mix is a huge pain, but with over 125 containers, I need to. I have 35 figs alone. 125 was last year’s total, i added 30 more plants, maybe more, too afraid to count,:slight_smile:


I bought the bricks that expand, I think I even found some at a pet store sold as reptile bedding. I do small plugs first then bump them up into real soil, it cuts my coir costs.

I had success with the peat based mixes as well, I just find that the seedlings in coir need less monitoring.


The 4cf bales of promix BX went up at the local nursery from $30 last year to $40 this year. Quite the jump!!! What do you guys pay where you are at? I am in Bismarck, ND…


Promix is $33/bale here


I find that peat-based mixes such as ProMix are great for seed starting, but after a couple of months it begins to break down. Small particles dominate at that point and it becomes a puddling. ProMix has a wetting agent and small charge of fertilizer, making it ideal for starting only. Recently the price of ProMix has skyrocketed, so I found another brand that is very similar in make-up. For longer-term container plants, I find a pine bark based mix to be ideal. I mix my own using some compost and controlled release fertilizer.

I spent hours reading up on the Container Gardening forum over at our old haunt. Al is a font of knowledge. I also recommend Whitcomb’s work on container growing.


I was looking for Whitcomb’s potting mix recipe at the Rootmaker web site and couldn’t find it, although I’m pretty sure if I kept searching I would have found it because I stumbled on it recently. I did run into some interesting stuff for container growing nerds. Many articles like this one are available at the “Knowledge Center” of the site.


Heres a decent price on Coir for those who are fans. I ordered 4 blocks recently, cant beat free shipping!