We call the medium in which plants grow, “soil”, Dirt is what you get on your clothes!
Dirt or soil may all be the same to you, but believe me, to your plants there is a world of difference.
The best soil mixture for starting your seeds indoors, or using in your square foot garden is:
1/3 good quality compost.
Let’s talk about compost first. I compost in my back yard. Its a great way to recycle kitchen scraps, leaves, grass, anything plant organic. Notice the word “plant”. Put your dog poop in the garbage.
When we compost, the organic matter (kitchen scraps, leaves, grass) is broken down by bacteria. You need a moist (not wet) place for the bacteria to thrive. The bacteria releases heat as it digests the plants. If the internal temperature gets hot enough (140º – 160º) long enough (15-20 days), it can kill weed seeds in the compost. The problem is that in the home compost bin, there is often not enough heat generated to kill off the bacteria. So, the compost that you make in the back yard may not be sterile.
Commercial and city compost yards are constantly monitoring the temperature of their compost piles to make sure the compost gets hot enough to become sterile. So, when you buy the compost, ask questions. Is this sterile compost? If they can’t assure you, move on. Our local compost company has a big sale in the spring and that’s when we buy the whole season’s worth.
Next; Sphagnum moss (also called peat or peat moss). This is organic in nature, is harvested from peat bogs in which it has been layered for centuries in the ground. It is acidic in nature and absorbs tons of water. Bales or bags of peat from the local garden store can be heavy. Buy sizes you can manage. Remember the peat expands when you open the bale.
Finally, vermiculite. Interesting stuff. Actually a mined mineral. It has many uses for the gardener, besides being 1/3 of the best soil less mixture ever. With this mineral in the soil, water is absorbed and when starting seeds, very little watering is needed. This mix provides great root growth and is loose and friable, meaning the plants grow easily in it. This loose nature allows air to be available to the plant which is more important than you might think. Vermiculite is also an accepted medium for hydroponics.
Superhero Note*** In the fall, do you dig up your dahlias? Well storing bulbs, onions whatever in vermiculite keeps mold and mildew from growing on the bulbs. It does not take up moisture from the bulb, but it does pull moisture from the air and prevents rot from occurring during storage.
Using our recommended soil mix in the garden can mean no weeding! Really, no weeding. There are no weed seeds brought in with it (remember what we said about the compost?). Weed seeds can be dormant in the soil for years and years, so in normal garden soil, you are always pulling weeds.
OK, so now you have to mix this all up! keep your batches small, because it can get to be a lot of work. The materials are quite dry, so you may want to mist some to keep the dust down, just don’t get it soggy, or you won’t be able to lift it.
A cement mixer is ideal, but not everyone has a cement mixer. A wheelbarrow and a shovel can do the trick too.