Since we have been having some great conversations lately about windrows and other outdoor vermicomposting systems I thought it would be a good time to mention that in some states, including mine (MN) it is illegal to dump non-native species. That is kind of a "non-sequitur" because there are no known species of worms that ARE native to MN, but nonetheless, it is illegal to dump them.
The problem is that our hardwood forests developed without the presence of earthworms. The forests create a top layer of "duff" (leaves and other organic debris) which seedlings, ferns, and wildflowers depend on in order to grow and thrive. The earthworms can destroy that layer by eating all of the organic matter, at which point the regeneration of native plants is slowed or eliminated.
For that reason, it is illegal to "dump" worms. Releasing red wrigglers or other worm species into windrows or compost piles is the same as "dumping" them. I don't use windrows because that system does not meet my needs, but if I wanted to I would only use them indoors on a concrete floor where the worms cannot escape to the great outdoors. I have taken great pains over my many years of vermicomposting to "cure" my vermicompost long enough that all cocoons have a chance to hatch and the baby worms grow large enough to be found and removed before I use the castings in my gardens. Admittedly, I did that long before I became aware of the illegality of dumping worms and my reason for doing so was more to not "waste" any of my worms than with any thought to the environment. But hey, we live and learn, lol, and I do want to be the best steward of the environment that I can possibly be, especially on and around my own farm.
For others who are worming in northern climes, here is a blurb that I am copying and pasting from the Minnesota DNR website-
"Non-native "red wiggler" earthworms are sold and shipped all over the
country for home compost piles and vermicomposting (worm composting)
operations. Thus far, they are not known to survive Minnesota winters.
However, if they or other species are able to survive winter and escape
from compost piles they could further harm native forests. If you have a
compost pile in a forested area, do not introduce additional non-native
earthworms. If you are concerned about spreading non-native worms with
your compost, you can kill worms and their eggs by freezing the compost
for at least 1 week".
That might give pause to anyone who is thinking about establishing windrows for worms in the North, at least here in MN. I don't know if it is true that Eisenia Fetida cocoons will not survive our winters or not because I have never tried it, but the DNR seems to think that they will not.