Seed starting mix vs potting soil – Part 2

The results from my soil experiment are in. It’s a real head-scratcher.

soil experiment results

(seed starting mix left, potting soil right)

Kale: The Kale in both seed mix and potting soil germinated the same day, and grew at the same rate for a week. After two weeks of growth, the seed mix kale is far outpacing the potting soil. Winner: Seed starter mix

Spinach: None of the seed mix spinach germinated at all. Four out of 6 seeds germinated in potting soil. Winner: Potting soil

Lemon Balm: No lemon balm germinated in either soil mix at all. I think this is because I failed to score the seed coat properly, but I’m not really sure. Winner: no one

Final Score: Potting soil – 1, Seed starter – 1

So there’s no definite winner here, and I don’t feel like I really know why I got the results I did. I thought I did a great job making conditions the same for both cell packs of seeds, but maybe it wasn’t equal. Maybe some seeds do better in seed starter mix, and others do better in potting soil. I’m going to think about this a bit and retry my experiment again soon. If you have any ideas/input about how I should go about my next trial, please let me know in the comments section.


Update: Please also check out my previous post on the topic Seed starting mix vs. potting soil as well as my more recent post More thoughts on potting soil vs seed starting soil

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4 Responses to Seed starting mix vs potting soil – Part 2

  1. Quiltedtime says:

    I am glad that you did this experiment, because the results are very typical of what I have seen. Sometimes I am disappointed, and other times, I am thrilled. The only time I use either potting soil or seed starter is with squash and some flower seeds. That allows the seedlings to survive the birds and snails, who just waiting for those sprouts to come up in the garden so they can make a meal out of them.

    • Susan says:

      Living is such a cold climate with such a short growing season, I have to start most of my seeds indoors to give plants enough time to produce something edible. Beans, peas, and carrots are pretty much the only ones I direct seed outside, just because they don’t work well at all to transplant.
      I think its possible to get a “bad bag” of mix from time to time as well, which you can’t really help. But I’ve used both of these bags for several other things, so I know in this case they are not “bad”.

  2. Aurora says:

    Commercial seed composts are so variable! I am trialling a few this year to see the differences. I don’t honestly believe that they are any better than multipurpose composts.

  3. Pingback: Seed starting mix vs. potting soil » Dig | Sew | Grow

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