Long ago, I attended a master gardener training on container gardening. My big takeaway from that was the idea of soil mixes. I was amazed to learn that many people don’t just use the soil as-is from the bag that they pick up at the garden center.
The recipe that I learned is:
- ⅓ potting soil
- ⅓ peat moss
- ⅓ pumice
My friend and fellow gardener is the one who I think started calling it “the blend” and the name stuck. Sounds like coffee and I can ALWAYS get behind that!
For a long time, I stuck to the recipe because I thought, “Who am I to mess with a master gardener’s recipe?”
After living in several different regions of the country with varying access to ingredients, I have modified this a bit. Pumice has been impossible for me to find outside of Arizona. There are potential sustainability issues with using peat moss. And that proportion isn’t a hard and fast rule. I’ve learned that it largely depends on the quality and type of potting soil that you start out with. Also, different plants–indoor vs. outdoor and cactus vs. tomato plants–have different needs.
Also, Google soil recipes and explore the wonderful world of gardening. There are so many soil mix recipes on the Internet; I’ve tried several, and a few were a complete failure for me.
So I hereby give you permission to experiment. Use this recipe as a guide rather than a hard and fast rule. Explore other mixes or go by feel and texture. Observe your plants and ask yourself, “Are they doing well? How’s the drainage?” If you see issues with plant growth or waterlogged soil, you can adjust the recipe. I have been known to re-pot a plant to amend the proportions of soil, peat, and perlite.
Now my recipe is probably more like this:
- ½ potting soil
- ¼-⅓ peat moss or coconut coir
- ¼ perlite
This year I purchased some compressed blocks of coconut coir that were fantastic–and I bought a few that were less so. Same goes for potting soil–I have had some bad blends that I thought needed more work than they were worth.
For my vegetable container gardening this year, I added compost to the mix or used a compost-amended potting soil that I LOVED. I wish I had purchased 10 bags of that stuff. So far my plants are doing well, and all the tomatoes and peppers are setting fruit. The eggplants haven’t yet decided if they are going to play. (Pacific Northwest Gardening is an adventure. Especially compared to other places I have gardened, June and July were downright cold.)
My go-to potting soil is Kellogg Garden Organics Raised Bed & Potting Mix. I don’t like it on its own, but when it’s part of the blend, it feels perfect to me.
I buy huge bags of perlite from Home Depot or a local garden supply center that I like that has perlite in sizes that I didn’t know existed before I walked through their doors. Wow.
I do add a cactus soil to the blend when I am potting cactus and succulents. I don’t know if it’s essential to do this–maybe adding more perlite would be sufficient, but I tend to rely on the bagged cactus mixes as an ingredient and that works reliably.
A note about perlite: You absolutely don’t want to breathe in perlite dust. Wear a mask, or better yet, wet it down completely before handling it. I spray it down in the bag or as I am pouring it into my soil can. (I used a large lidded trash can with wheels for my blend.)
If you used compressed coconut coir, put it in a wheelbarrow or a trash can to soak it and give it time to expand. Give yourself time to soak it, tease it apart, soak it some more and repeat until it expands to its full size. (A coir brick the size of a large paver will expand to about two cubic feet.) It’s an easy and satisfying task to tend to while you are doing other things.
Experiment with your soil mix so that it suits your plants and your growing environment.
Keep going and keep growing!