Q: I wanted to know if the soil has a shelf life, how long can it be left unopened in the bag before it is no good. I have a bonsai tree that I will repot but I probably won’t use all the soil. I will have to pot another about a year from now. Will the other unopened 2 quart bag of soil last until i am ready to pot the other trees next spring?
A: Our soils are blended using dry components. In its dry state, they don’t break down or deteriorate at all. The soil just gets really dry until it’s used. Therefore we try to bag it while it’s dry. So when it’s used, it has to be somewhat reconstituted with water to make it like normal, moist soil.
To keep the soil usable for a longer amount of time, we keep it dry as long as we can before we package it. Occasionally, mostly when the weather is wet and cold, the soil will ship out a little moist and condensation forms. This really doesn’t make much of a difference in the short term, but if it stays closed and wet, the organic matter in the soil will continue to decompose and will actually eat the air in the bag, eventually sucking it down to a brick. We poke a small hole in the package to prevent this from happening.
In either case, if you’re going to keep the soil around for a while, it’s best to make sure the bag is at least a little bit ventilated to keep things dry. If you live in a very wet climate, that' would be difficult to do over the long term.
So, I guess the answer about shelf life is more no, than yes. I don’t think a bag you’ve had for a year would be any less usable than buying a new bag.