Garden soil is for sale most months of the year, even in my cold area, but I tend to repot a lot of plants and start cuttings or seeds so I make my own soil. You do need a certain mix for your indoor plants and indoor gardens. When you use garden soil indoors it tends to turn hard.
Houseplants can’t thrive in cement-like soil. They need sufficient drainage and aeration. Tough soil will also tends to stunt the plants roots. Houseplants also need nutrients to grow healthy and strong.
With a few materials, you can easily make your own indoor plant soil.
Mix together two quarts of clean sand, topsoil and peat moss in a bucket. Mix in 1/2-cup charcoal and 1/2 cup perlite.
Stir in just enough water to make the indoor plant soil damp. Place the soil into an old, large roasting pan. I picked up such a pan at an auction. It’s my “make a mess pan.”
Level out so the soil is not more than four inches deep. This gives you an even cooking depth. If your mix is deeper than 4 inches, divide it into two pans.
Preheat the oven to 180 F. Next place a potato down deep into the center of the pan. It should be completely covered with soil. Cover the pan tightly with aluminum foil.
Make a small hole toward the center of the foil, but away from the potato. Place a meat thermometer through the hole and into the soil.
Place the roasting pan of soil into the oven. When the meat thermometer reaches 180 F, set the oven timer for 30 minutes.
Remove the pan and check the potato. If it’s cooked done, that means the heat of the oven passed through the soil successfully. Your indoor plant soil is now sterilized. Allow it to cool before you use it.
This may seem like a lot of effort, roasting your soil. But you need to kill any disease and you need to do it at a moderate even temperature. Too high of a temperature will kill good soil properties.
I have made soil for years. It extends my supply of planting matter and I have very healthy seedlings and plants.
Notes: It’s even wise to precook the soil you buy in a garden center. It occasionally carries bugs and dormant seeds.
Once you have a feel for creating your own soil you can add a little fresh compost to the mix for freshening soil in planters or feeding new seedlings .