Would an earthworm die if I put it in my container filled with potting mix or would it survive and benefit the plant?
Leave the worms for the raised beds etc.... Do a search, there is at.least one other posting regarding this with some good info.
Too me container gardening and organics are almost an oxymoron... containers are to plants what a fish tank is to fish
I had some pots on the ground and worms entered them through the drain holes and did quite well. The soil was mostly my own compost though, and the pot was very large so it stayed moist. If your pots are small enough that they might dry out before you water them, then the worms might not do well in them. And I have no idea how straight, new potting mix might effect them, but I think it's probably worth a try.
If they live, it's much more likely the worms would end up a limiting factor, rather than a benifit to your plants. Worms feed on organic soil particles, reducing their size and destroying soil structure, and their castings exacerbate the process. The soil collapses, reducing aeration and slowing drainage while the castings fill in pores and increase the rate of collapse. The increase in the ht of the perched water table is primarily where the actual limitation comes in, and that is directly related to compaction, as well as soil aeration, the lack of which would also be limiting.
Earthworms get into my potted plants all the time. I've never seen them causing a problem. I think they would be better off in the soil, but there is no way to stop them from getting into the pots in my yard.
I grow many things in various potting mixes from commercial to home made to straight compost. There are earthworms in almost all of it. I consider that a sign that my various mixes are healthy. The plants do well too.
When I read tapla's Al posting regarding earthworms in containers, I was struck with the fact that everything he said regarding containers and earthworms, was exactly opposite of their role in your garden. In your garden soil they improve the structure, their castings enrich the soil, and they help prevent soil compaction. This brings to mind how different container gardening is from gardening in the ground. Al
Having live worms in a container is indeed a sign that the medium is healthy ..... for worms, but is no indication that it is healthy or even a good choice for the plants, or that if it is currently healthy that the worms won't quickly make it unhealthy for plants, and perhaps even for themselves.