Mixing Your Own vs. Using Bagged Potting Soil: Which Grows Plants Better?

Why Should You Consider Mixing Your Own Potting Soil

If you’ve seen our article or video on mixing your own potting soil, you may know that we are big fans of homemade potting soil mixtures and the benefits they provide to small and medium-scale home gardeners. While many dedicated gardeners mix their own potting soil, we realize that mixing your own potting soil can be a big leap of faith, and one that implies a significant tradeoff between the time and energy invested in doing so, and the benefits received from your homemade mix versus just buying regular old bagged soil.

The Setup 

Well, we had all this nice homemade potting soil after filming our Mixing Your Own Potting Soil video so we decided to run a little “casual” experiment to re-check and document an intuition that we’ve had: quality homemade potting soil outperforms bagged potting mixes. We tried two of our mixes alongside three popular store-bought bagged mixes. 

Results: Homemade Seedling Mix vs. Homemade Veggie Mix vs. Bagged Soil

In this experiment, we had demonstrably better results with our in-house potting soil blend as compared to bagged potting soil blends. We promise the pictures included are not cherry-picked, and we would be happy to provide you with the experiment design should you reach out to us with an intent to recreate it. We used Genovese Compact Improved Basil from seed, all seeds were started at the same time, and all plants received the same amount of water. We should mention that there was actually more than one bagged soil blend included in the experiment, but two of them did so incredibly poorly that we genuinely felt it would be unfair to put them on blast without a larger sample size. Anyways, here are some results we had:

(Left to right): Homemade Seedling Mix, Homemade Veggie Mix, Big Name Bagged Soil

Results of Including an Organic Nutrient Boost

The three mixtures you’ll see here are our seedlings mix, herbs and veggies mixture (both from our blog on mixing your own potting soil), and a particularly popular bagged soil mixture that we will not name directly due to their massive legal resources.

W/ added fertilizer vs. worm castings only

Brand name bagged soil

Besides the large disparity between our homemade potting mix and the bagged blends, it is also interesting to note the difference between the seedling mix and the herbs and veggie mix. Because the herbs and veggie mix was designed for mature plants, it contains more nutrients, and therefore the leaves of the plants grown in that mixture display fuller color than those grown in the seedling mixture. The seedling mixture will produce plants that are more obviously nutrient deficient after a few weeks, whereas the added nutrients in the herbs and veggie mix will sustain the plant up through maturity.

Note the greener color of the plants with additional fertilizer (left) as compared to the basic seedling soil blend (right).

Want more? Have any clever ideas?

This was a very casual experiment we did – and we were kind of blown away with what the results might hint at. We’ll definitely continue this line of inquiry using plant clones and some duplicates – but is there anything else we’re missing? Favorite mixes or soils you’d want to see us include in our next round of testing? Any bone-headed mistakes you see? 

We’ll be sure to check the comments before starting up another round – so please leave your ideas/thoughts/criticism there!