From an article in Scientific American many years ago, there are many species of earthworms, and the way it worked in America is that wherever Polish immigrants settled and farmed, there were the same species as found in Poland, same for all ethnic groups.
Of course, they all used outhouses, so if you sneak some of your shit into your garden you shall have the right kind of worms for your kind of people. For free.
God's plan, IMHO.