I made my own seedling potting mix. It has 35% drainage and 65% water hold matter. Now, that I see it, I feel like it has too much drainage. I used roughly the same percentage of as Sungro's Blackgold Seedling Potting Mix. I have used Blackgold with great success in the past.

I know there are many potting mix formulas out there. I know everyone has their own preferences. So, I want to focus on industry standards. What is the industry standard of Inorganic:Organic Matter in seedling potting mix?

1 Answer 1


I do not believe there is a set standard. Each soil company will use different formulas. At the same time they will all have similar percentage of inorganic ingredients. You can safely assume that the other soil companies use something similar like 30-40%.

If you are worried, test your germination/seedling mix with the easiest seeds you were planning planting at this time or just use any quick to germinate seed. See if they germinate well. See how often you have to water. Grow them out for a few weeks before you start your other seeds.

  • Note that every seed has plenty of nutrients within. So drainage is at least as important as nutrients: pure sand may even work. Commented Jan 15 at 14:46

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