This would likely go in the basement, not be left outside, although with enough volume of material to insulate the worms it might work outside just as well. It is not super cold here in the winter for the most part, plus urban heat island effect, but we do have some quite cold spells in the winter now and again.

The worms will likely not find much to feed on in the discarded potting soil except the leaves. Also will depend on what your potting soil is composed of - just regular soil? But overall, mixing vermicompost (castings) and potting soil will rejuvenate it. What I've done is add soil from potted plants (stuff that's dried out and hard) into compost and/or vermibins, mix a bit and give it a while. It gets integrated nicely. If adding to compost, I found better to add to compost that's mostly 'done'. Experiment to find the right mix.

I should be more clear - none of this is "soil" as in mineral soil, it is all potting mixes of varying provenance, now full of pot-bound plant roots at the end of the season. The idea is for the worms to process the plants and roots, not so much the potting mix itself (which presumably is near the point where all the organic matter is getting to be humus that won't break down any more).

The potting mix I buy now is good quality organic stuff that already is made of compost with some other ingredients, including worm castings, so there wouldn't be much additional benefit to buying more of it then mixing in VC from my main worm bin. What I'd possibly like to do is keep the potting mix separate so as to re-use it straight, without the need to buy more each year. Can't pot plants in straight VC, so there is value in retaining the original potting mix, but I also think the worms might not need all winter to eat the plants and roots. Maybe only a small quantity of worms for this project.

Well, can't hurt to try. What I'd do is add some vermicastings, with some worms in there, and maybe add a bit of 'proven' worm food, and see what happens.

I like this idea, and hope that it works out well for you! Please us updated on how it progresses and how the worms react.

We think alike. I am going to dump my porch potting soil into my worm bin, and let them eat the roots....but also still use kitchen refuse as well. The plan is to use new potting soil with worms castings in spring again.

The large bucket of used potting soil (potting mix) on my back patio is sheltered from anything severe like wind or snow - it's under the overhang created by the balcony above me and in the corner formed by two walls. At the end of the growing season, I dumped out my outdoor container plants into the bucket (the pots were mostly very full of roots), sprinkled in some water, and added some of my overflow kitchen scraps and a very small quantity of red wigglers from my basement worm bin - probably no more than 50 worms total, in about 10 gallons of material (the bucket is a 13 gallon container, but it is not full all the way.)

It has not been a very cold winter so far, with plenty of days above freezing, but some stretches where it hasn't gotten above the 20s for several days in a row. Right now it's in the 40s and raining. From time to time (when it's not so cold), I've looked into the bucket and dug around a bit, and I always spot at least a few pink wiggly worms in there. I think it would have to be a whole lot colder for a lot longer at a time for the bucket contents to freeze solid all the way through, and that's unlikely to happen here, so the worms probably just huddle at the center and nap when it gets well below freezing out. The potting mix in the bucket is lightly damp but not soggy.

My plan is to check again when it's getting close to outdoor planting time, and if there is still unprocessed material in with the potting mix, I'm going to mix it up and add a few more worms for the last few weeks. I have a compost sieve I can use if there's still anything left like large twigs. I didn't want to add a full load of worms as I would with a regular worm bin, since they have all winter to work on the small amount of food that's in there, and I also don't want to have to pick out tons of worms before I re-use the potting mix.

The worms will need a sustained amount nutrients[food] and when the supply is gone they may look elsewhere or leave the bucket. You have to keep the worms happy..

Yes, I agree. Maybe sprinkle some oatmeal on top?

No, there is plenty of food in there to last such a small number of worms multiple months. In addition to the roots and plants and microorganisms that were filling the pots, there was at least a gallon or two of food scraps.

Last winter I did a similar experience , but in the end it didnt work out as I had hoped. I used a 1 gal pot with cutting, possibly the pot was too small. I had maybe a couple dozen wigglers and kept a small amount of food mixed in the pot. by winters end the worms were mostly dead or had left the pot. A larger pot would have worked out better.

My verms and I are awaiting spring. After so many days of weird 70 degree plus weather in February and into March, I was beginning to think winter had missed us entirely. But now the temperatures are below freezing again, and there's a big snowstorm predicted for Tuesday. We might get a foot here in Philly but New York and points north will probably get worse.

I goofed on my potting soil experiment, because I didn't put a good enough cover on it, and water got into the bin and waterlogged about the bottom half of the material. There were still a few surviving worms, but I couldn't find most of the few dozen I had initially put in. I drained the excess water and mixed up the material, added a few dozen more worms and put a better cover on it. There was some anaerobic stank, but it dissipated quickly. I did this during warmer weather, and I anticipate with the return to freezing temps that the worms will huddle in the center of the soil in the bin and wait it out. It's unlikely to freeze solid all the way through.

Our last frost date is supposed to be about mid-April, so I'll see how things are doing in a few more weeks. It seems that the few plant stems and roots that were more woody (such as the remains of a rosemary plant) have not broken down very much despite all the warm weather days. I'm thinking that such materials would be better off just being yanked out and processed through my worm factory indoors, where the temperatures are warmer and the worm population large and active.

Worms won't be able to do much with woody stems and roots until they're broken down further - just too tough for them. I'd just yank ,em.

The key is whether the system can work through woody materials in the time frame you want...in this case, "by spring" is not a reasonable goal.

Well, I was a little too optimistic about the extra moisture in the potting soil bin being gone. Either I didn't get it dry enough the last time I dumped it out, or more water got into the bin...or both. The bottom of the bin was still soggy and became stinky again.

So I'm having to violate my staunch "make the worms do the work" principles and get in there again, dump out and dry the contents of the potting mix bin, and try and shove the whole mess through my compost sieve to remove all the twiggy clumpy bits and salvage some usable potting mix. There are definitely still plenty of worms in the bin, and what's coming through the sieve is good stuff, but I should have just sieved it in the fall when it was dry, because sieving wet stuff is the pits....and I'm having a tough time finding enough rain-free days to get the stuff dried out thoroughly.

I'm re-making a bin to stay outdoors on the patio and receive my garden waste, but this time I'm actually drilling holes in the bottom, and I'm not going to incorporate old potting mix in there - it just holds too much moisture, which is then really hard to get out. Better to let the outdoor bin run as long as it needs to, and just separate dead plants from used potting mix when it's dry, and blend in some well-processed worm castings before reuse.

Since I did a similar experience last winter and I realize the bucket was too small for even a couple doz. worms. I would think it may work better by dumping your excess potting soils into a larger container or vat with no bottom and worms could come from underneath into the soil, you also would need to add food and they will come.