Potting Soil: Why NOT To Use It For Seed Starting

As of now, if you are into gardening you’ve probably already started some seeds to grow into plants.  If you haven’t started your seeds, it’s not too late!  On this post, I want to talk about potting soil and why NOT to use it for starting seeds, especially tomatoes.

I say tomatoes because this happens to be the vegetable that I discovered this phenomenon while starting my plants.  Around the end of February, I started my tomato seeds in seed-starting box.  However, the only soil I had around at the time was potting soil.  I figured it looked the same as regular ‘dirt’ so it should be alright to use a medium to start my seeds.

It worked okay to start the seeds, but after the majority of the plants dawned their initial leaves, their growth start to slow.  They still look healthy and green, but they just didn’t shed anymore leaves or grow in general.  So, this is when I decided to grab some soil from outside.

I conducted an experiment of sorts.  I kept a third of the seedlings in the potting soil, a third was immediately planted outdoors, and the final third was planted in the soil from outside but the containers were kept inside right beside the seedlings in the potting soil.  I wanted to see if the soil conditions were hindering the plant growth in any way at all.  The results were astounding.

Comparison of tomatoes in potting soil and outside soil showing the growth after the thinning stage.

As of today, the seedlings in the potting soil still look healthy, however they haven’t grown at all since the thinning took place.  The ones that I planted outside have grown marginally, mainly due to the cooler nights.  But, the seedlings that I placed in the outside soil and kept inside have grown tremendously.  Take a look for yourself!

My conclusion is this-  Potting soil will only ‘maintain’ a plant’s current growth.  There just isn’t the right amount of nutrients included in the soil.  “But how did the seeds turn into seedlings in the first place?”  During the germination process, the taproot uses the seed as energy to grow into a seedling.  It’s a compact feeding system on it’s own, however, once it reaches a stage where the seed has exhausted it’s energy it needs outside nutrients.  Potting soil doesn’t have these needed nutrients.

How is your experience with potting soil?  Have you actually been able to ‘grow’ anything in potting soil?  What’s your thoughts on the ‘matter’? 🙂