ManyTracks Homestead - Homemade Potting Soil for the Greenhouse Garden

Making Your Own Potting Soil by Sue Robishaw

        I’ve tried a lot of different combinations for potting soil in years past -- from store-bought to elaborate homemade mixtures that took hours and a motorized shredder/grinder to mix. Buying dirt in a plastic bag just isn't my thing and the noise of the shredder was hardly a pleasant experience (besides which we sold it). I decided I was making this project far too complicated and too hard, so I looked around for another solution.
        Well that solution was easy and right near at hand. The compost pile.
        We have two garbage cans in our greenhouse which are filled each fall with compost trucked from the compost pile in the garden via wheelbarrow. And that's it. In the early spring I sift the compost through a 1/2" hardware cloth screen, then through a 1/4" hardware cloth screen for fine soil for planting seeds. Sometimes I'll mix in some sharp sand if I have it. When it comes time to transplant I might sift the compost through the 1/2" screen for the flats, or I might just take it straight and pick out the larger lumps, depending on the quality of the compost and what I'm feeling that day. For larger flats and pots I use the compost straight.
        The plants and I are quite happy with the results. I spray the seedling flats with a strong chamomile tea and that takes care of any damping off problems. Chamomile is easy to grow (I just let it self sow in the garden then let a few plants grow here and there). When I'm done harvesting blossoms for tea for myself, I pull the whole plant and dry it for the tea for the seedlings.

2004 UPDATE

The above little piece was written written years ago and updated in 1998. Now it's almost 2005 and I have a bit more experience. I still use compost as my main potting soil ingredient [see the Compost article], but over the years I've found it often to be too heavy for the greenhouse plants. So now I'm back to adding a bit to the mix. Also, I've found it easier to screen it all before storing. I have a nice homemade, wheelbarrow size 1/2" hardware cloth sifter that makes it easy [see Sifters article]. As with many cooks, I have no exact recipe, but I shovel in and screen maybe a third or half wheelbarrow full of compost, then add several shovels of sharp sand, and generous dusting of wood ashes, a few shovels of old sawdust, and several generous handfuls of screened, shredded old dry leaves and well dried clippings (run over several times with the lawnmower). Mix thoroughly with the shovel and store. This has worked well, though I sometimes get some white mold on the flats. This isn't the same as damping off, as it doesn't seem to bother the plants. But it bothers me, so I often will put the dirt in the flats and pots then water with hot water before planting (letting the dirt cool off first, of course!), which seems to eliminate the mold.

Now, I've also potted up small transplants and full sized plants out of the garden to bring in the greenhouse in the fall, using plain garden soil and they have done just fine. But my experience using garden soil for indoor winter and spring potting soil hasn't been good, so I don't include regular garden soil in my mix. It tends to pack too much and I had more trouble with damping off when I used it. I'm sure this would depend on your soil, however, so experiment.

One way or another, there's no reason to BUY potting soil, particularly that packaged in non-disposable, landfill-filling plastic bags. Make your own! If you eat, you can make compost. If you live where you can't have a regular outdoor compost pile, check out the indoor worm composting method. Healthy plants and healthy people start with healthy soil!

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Updated 10/19/2006

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