Back in February, I saw Erin with Floret Flowers share on Instagram about her seed-starting recipe mix which produced more robust seedlings that could stay in the cell trays longer if need be. I sow a LOT of seeds each year, so I thought this would be exactly what I needed! I would love to skip the potting up part and just plant the seedlings after they’ve grown some.
So, I went to her site and put in my info to get the details on the recipe, which are as follows:
- 1 3.8 cubic foot compressed bale of Pro-Mix BX
- 5-gallon bucket of high-quality, screened compost
- 6 cups of bonemeal
- 3 cups of kelp meal
- 2 1/4 cups blood meal
I had to do free ship-to-store at Ace Hardware for the Pro-Mix as that was the cheapest option online and no one in my county carries it in stores. I bought a cheap $7 6×8 foot tarp at Walmart for the mixing, a 45-gallon tote to store the final mix in, and a small utility shovel (worth it!) that I can also use for other mixing purposes later on. Before I could get to mixing mine, I started seeing people posting mixed reviews about it in a cut-flower Facebook group I’m in. Some said nothing germinated in the mix. Some said the seedlings died off promptly after germinating, while others noted the algae/fungus that appeared rather quickly on top of the soil (especially with the organic fertilizer components).
So, I decided to half the fertilizer ingredients so it would still provide some nutrient but perhaps not burn the seedlings. I got the tarp and shovel and spread the ingredients all out evenly over the tarp.
Pro-Mix on the tarp:
This is the compost I used (also ordered and shipped to Ace Hardware).
I did not screen it. Ain’t nobody got time for that! I also bought two 1-cubic foot bags because I didn’t know how much would be needed for a 5-gallon bucket. One bag was more than enough.
As for the fertilizer components, the bone meal and blood meal came from Lowe’s, but I had to order the Kelp meal on Amazon (affiliate link) since no one carries that around here.
I screwed up the measurements when distributing the fertilizers, so this was my final recipe:
- 3.8 cubic foot compressed bale of Pro-Mix BX
- 5-gallon bucket of Black Gold Garden Compost blend (not screened)
- 3 cups of bonemeal
- 1.5 cups of kelp meal
- 1.5 cups blood meal (ooops, should have been 1 1/8 cup)
I wanted to use the tarp and shovel to make sure things were distributed evenly and mixed well. I thought perhaps one reason some may have had trouble with seeds not germinating or seedlings dying off immediately was possible ‘hot spots’ where there was too much fertilizer, so I mixed. And mixed. And mixed.
The entire recipe would probably fit into the 45-gallon tote if I pressed it down, but I usually fill a smaller tote (the gray one) to keep in the greenhouse for filling trays and inserts to start seeds.
If you do this, make sure it’s not a clear tote!! You do not want sunlight and moisture to build up in the tote or mold and algae will start forming. I store seed-starting mix all the time like this, and I never have an issue with mold or algae.
Since I’d read about others having issues with algae forming quickly on top, I used a little more vermiculite cover than normal to help with that.
The results: not worth it. I did not take any pictures along the way, so I don’t have any comparison photos. For the effort put into making the mix and obtaining the materials, I will not do it again.
Some of my seedlings did seem to do well, but they are the ones that did well in previous years in regular seed-starting mix (like impatiens, marigolds, & zinnias to name a few). I didn’t have trouble with germination. Honestly, the only way for most of the seedlings to grow bigger is to pot them up and give the roots more room to grow. This definitely doesn’t work with a 128-cell tray. You have to pot up the seedlings in order for those to grow bigger. Perhaps if you started them in a 50-cell propagation tray, they would do better growth-wise. I did not notice the difference Erin at Floret mentioned. Granted, I only used HALF the nutrients from her original recipe.
In the greenhouse, the algae on top wasn’t that big of a deal (but you can see from the above picture I really need to clean my greenhouse film!). In the greenhouse, algae was minimal. It was more pronounced on the seed trays in my grow room under lights, especially for seeds that took a lot longer to germinate. Some seedlings dampened off, but I think that is due to the massive fungus gnat infestation I had. I have been starting seeds for over 10 years, and NEVER have I had fungus gnats in my greenhouse this bad. Never again! The natural components of the fertilizers are magnets for them!
I meant to take a picture of the yellow sticky sheets I put up in my greenhouse to get rid of the adults. 4 large sheets, covered in a matter of days! I had to mix B.T. (affiliate link) into some water and water it into the soil to kill off the larvae to stop the cycle and get rid of them.
I am going to do some experimenting either this fall with seed-sowing or springtime next year, and I will share what does best for me.
