Sterlizing Dirt for Growing Microgreens in the Basement (January 2016)

A typical microgreen salad of ours with onions, cucumbers, apples, sesame seeds, carrots and crotons. 

 

We are in the middle of winter now and though our cold store is full of our canned goods such as pickled beets and beans, some carrots, pumpkin, various soups, jellies and jams, along with our stored potatoes, onions and garlic, it's nice to have some fresh greens.  Since our greenhouse isn't up and running yet and we currently don't have any cold frames, we grow microgreens on the growing shelves we use to start our seeds for the garden located in our basement.

For our dirt we used both our left over seed starter, and potting soil. The microgreens we are currently using are Mizuna, Arugula, Oriental Mustard, and Red Russian Kale. After a few rotations, it is time to sterilize our growing medium so it doesn't grow mould or any other micro organisms.

First, after removing any remaining plant material, we dumped our soil into a metal bowl.  Our dirt was almost powder dry so we added a little bit of water to help it heat up a little quicker. 

After preheating the oven to 300F,  we also stuck a probe (not all stoves has these) into the soil.  This was set to 200F. If you don't have a probe, then use a meat thermometer.  We then covered the soil with aluminum foil.  The soil needs to reach 180F and stay around this temp for a half an hour, and not reach to 200F.  For the size of the bowl we used, it took a good hour to reach 180F.

Once the dirt reached 180F, we brought the bowl out of oven, removed the aluminum foil, and let cool.  Once cooled we filled up our trays again with the soil.

The soil will be dry so we watered it, broadcasted the seed, lightly covered the seeds with another layer of soil and lightly watered it again.

Now our microgreens are ready for our grow shelf.  Our grow shelf uses T8 fluorescent bulbs, though there are grow bulbs you can purchase as well.  We find the standard T8 fluorescent bulbs work just as fine for us. Each shelf has one 'warm' and one 'cool' fluorescent bulb so the plants get a broader spectrum of light. Our lights are on a timer as well, and come on when our hydro is the cheapest (during the night). The trays are also placed on seedling mats to keep the soil warm and help the seeds germinate. In about 3 weeks we should be eating microgreens which taste great with some of our onions, seeds, slices of apple and raspberry vinaigrette!