This year I am try to be frugal in the garden, don't tell I blew the seed budget...... One large cost for the garden is potting soil, both for veggies and ornamentals. Last year I saved all my potting soil with plans to reuse it all this year. The problem this creates is seedlings need sterile soil and used soil can harbor all kinds of fungal and disease problems. With that in mind I googled' how to sterilize potting soil and here is what I found:
First off the used potting soil went through my compost screen to remove all roots, leaves, maple keys etc. With that done, place the potting soil 4" deep in a roasting pan that is not used for food. Top it with foil to seal the moisture in and then insert a thermometer to monitor the temperature. Then the whole lot went into a 200f oven.
Now monitored the thermometer until it reaches 170f, it took a good hour to heat to this point. Once at 170f hold the temp for 30 minutes which is long enough to kill off any nastiest and weed seeds.
A few words of caution: One, it kind of smells, but not to bad. Like an earthy peat moss smell and it does not linger. Two, it is important to not heat the soil over 200f or it can create toxins that will kill your seedlings. Make sure to monitor the thermometer. Three, this only needs to be done for seeding, for potting up you can just screen the soil. All in all it was a pretty painless procedure and saved buying a $10 bag of seeding mix.
4 hours ago