Seedling Organic Potting Mix
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Prices reviewed for value per ounce and quality (based on customer ratings) as of August 4, 2026.
If you've been starting seeds in whatever bagged mix was on sale, let's talk about why that's costing you more than you think.
I used to cut corners here. Grab a cheap bag, get seeds up, move on. But weak, spindly seedlings don't catch up later — they just carry that deficit through transplant, through the first hard week in the ground, sometimes through the whole season. Cutting corners on seedling vigor costs you far more in the long run than investing in a quality mix up front. A stronger root system at week two means fewer losses at week six.
This blend is adapted from principles in Daniel Mays' The No-Till Organic Vegetable Farm — available as a paperback or Kindle edition. I've been running it for several seasons, and the difference in root development and transplant shock has been noticeable enough that I don't go back.
One bonus: the fertility ingredients come in bags way bigger than what one batch needs, so you'll have plenty left over to build other blends afterward. It's not a one-and-done purchase — it's an investment that stretches across your whole season.
Black Potting Mix (makes ~2.5 cubic feet)
Ingredients
- 2 bags Hoffman Canadian Sphagnum Peat Moss, sifted to ½" — selected for best price per ounce with consistently high reviews
- ½ cup Lime — balances pH in peat-heavy mixes; good value per pound
- ½ cup Blood Meal — fast-release nitrogen; reviewed for cost per ounce and quality ratings
- 2 cups Alfalfa Meal — slow-release nitrogen and growth stimulant; strong value pick
- 1 cup Super Phosphate — supports root development; selected for price-to-quality ratio
- 1 cup Kelp Meal — micronutrients and natural growth hormones; best-reviewed option at this price point
- 1 (5-gallon bucket) Perlite — improves drainage and aeration; great cost per cubic foot
- 1.5 (5-gallon buckets) compost, sifted to ½" — use your own or a quality bagged compost
Steps
- Combine the peat moss, lime, blood meal, alfalfa meal, super phosphate, and kelp meal in a cement mixer — or the budget option: a large lidded plastic bin you roll or shake, or mix by hand with a shovel. Run for about 2 minutes.
- Add the perlite and sifted compost. Mix for another 2 minutes until evenly blended.
That's it — 2.5 cubic feet of mix ready to fill trays or blocks.
What I Start Seedlings In
For trays, I use TO Plastics 1020 trays with holes — durable enough that they don't end up as landfill after one season like the flimsy dollar-store kind. Reviewed for durability and price per tray.
And if you're tired of paying for plastic seedling pots every year, here's a reusable alternative worth a look.
As an Amazon Associate I earn from qualifying purchases. All product picks were evaluated for price per ounce and customer review ratings as of August 4, 2026.