I have 3/4 of a large bag of worm castings in my greenhouse that is 5yrs old. Haven't done any new plantings for that long
due to illness. I just discovered the bag the other day. Is it still good to use? It's gone through much heat and cold temps. I live high desert country...hot summer days,cool summer nights. And below freezing in winter. Worm casting aren't cheap.
Use it or toss it?
I don't know anything about the viability of the worm castings after 5 years but it certainly should be a good soil conditioner. Don't throw it away. Just add it to your soil and see what happens. It cannot hurt anything! I use it too and keep a bag for two years. I would think any mineral content in them would still be OK but I'm no expert!
Thanks for your input, gardore. I will use the worm castings. Like you said it can't hurt anything. I have an order of new plants I just got it. Two of which are viburnums. I will use the castings on one when I plant them and not on the other and see what happens. I'll let you know how it goes.
Wow, three months isn't very long. Maybe it's longer if the bags are not opened. The hydroponics store near me certainly has their bags more than three months. Regardless, they are still a good soil conditioner even if the microbes are dead! I just bought a new bag from the hydroponics store so am ready to go. It was very cheap $21 for 30 lbs. I can't even get it shipped anymore for that price.
I can't imagine that by applying worm castings you'd be introducing any microbial populations that aren't already present in a soil, so why worry about their viability? I'm sure the worms in your soil are currently pooping up a storm. All the microbial populations need to multiply is a suitable environment and plenty of food. And as long as you keep them dry, the nutrients aren't going to simply evaporate. I'd rate the shelf life of worm castings as indefinite if kept dry.