My composting worms are indoor creatures who live in a large plastic tote (holes in the bottom for drainage, area cut out in top and screened for air). They are red wigglers that I got at the farmers market in Concord NH. I'm not sure they can live outdoors, I would check on that. They are great for eating kitchen scraps (not meat), coffee grounds, used paper towels, etc. They will multiply if there is lots of food. If not, they just don't have so many babies. I have had enough to give to friends. Mine live in the cellar year round so I don't have to walk thru the snow to the compost pile. I doubt that they would harm living plants but my garden is full of what I call night crawlers. I wouldn't bother to add composting worms. The night crawlers help aerate the soil. Red wigglers are much smaller. They do a great job at quickly turning kitchen scraps into compost but it's mucky (probably because of all the coffee grounds I add) so it's hard to separate the worms from the compost. Last summer our little granddaughters thought it was great fun to pick out worms so I'll do that again this year so I can have the rich compost to put in planting holes for tomatoes etc.

If you want worms in your garden to aerate the soil, just apply a nice, thick, organic mulch like seaweed, chopped leaves, or natural (not dyed) bark mulch. When you come back and look next fall, the soil under the mulch will be full of worms. Of course this is assuming you have decent soil with a lot of organic material already in it.

I just turned 4 of my compost bins (to the dismay of my physical therapist!) and they were full of worms. This is despite the fact that I've never added a worm. The sections that had more "undigested" organic material had the most worms, and the more finished sections were a little less heavily populated. These "native" worms (OK, they came with the settlers and aren't actually native) survive in the compost pile over the winter, maybe because it's big enough that the center never freezes.