The community garden at our apartment complex consists of fill dirt, high clay content, shale shards. I dug holes and filled them with potting soil to plant some roses, lilac bush, etc. Nary a single earthworm seen!
Is it feasible to introduce them a plot-at-a-time?

Most worms are down deep to keep from freezing, wait til the soil warms However, not sure making holes in clay will drain well, fill dirt just needs composts and mulches

Agree with above...
instead of digging holes and adding potting mix... suggest finding a large amount of mulch (I use woodchips).
Spread mulch on top of entire bed several inches deep... wait... you will see earth worms like mad in a year or so...

As they've already correctly answered: essentially the more organic matter you add the more worms will be attracted. Whether wood chip mulch, shredded leaves, untreated lawn clippings (preferably mixed with some other coarser material), straw - the list is long - all will serve the purpose. Some gardeners would dig the material into the soil, some would mulch only. I prefer lightly forking a bit of material into the top few inches AND adding a generous mulch. Your soil structure will also gradually improve as worms come to the surface and carry matter down. And don't forget - let no pile of Autumn leaves go unused. If you can shred them and use as a winter mulch they are great or if shredding with a lawnmower isn't an option you can even create leaf mould over a year or two by simply bagging them while damp (punch a hole or two in the bags with your garden fork) and allowing them to rot in a corner behind your shed for a year or two.

Worms are there, you just need to give them a reason to hang around and multiply.

Ummm, by the way, when it gets a bit warmer, add maybe 1/4 to 1/2 cup of USED coffee grounds. It is worm candy trust me.

kittriana said:Ummm, by the way, when it gets a bit warmer, add maybe 1/4 to 1/2 cup of USED coffee grounds. It is worm candy trust me.

It is funny you say that - a well respected gardening program recently weighed in and said that worms don't like coffee grounds and that they, gardening 'experts', would not add them to their garden beds...but saw no problem in adding them to the compost pile where they would be 'diluted'. My experience from the days when I kept a large vermicomposter was like yours. Wherever the coffee grounds went so did the worms. But then I was living in Seattle in those days and maybe even Seattle worms are caffeine addicts.

I agree with adding the coffee grounds. The worms in my compost bin eat it up. Also eggshells - I can never have enough egg shells for them. I just crunch them up just a bit - one squeeze with my hand is all, and throw them in the bin. They are usually gone in a day.

Lots of people don't NEED worms in small containers, worms and roly poly bugs have the job of eating dead vegetation, but if there is no dead vegetation, both of these will happily chow down on the roots of a plant, doesn't seem to even affect the plant except it will have no roots. I use the coffee grounds in a different way- I throw them where it draws moles after the worms AWAY from my garden, chuckl. Yes it works, and used grounds disintegrate rapidly, cause no ph imbalance, and can be washed before adding if needed so that they simply become vegetative matter. Eggshells- I have dug up half egg shell forms and find they are used as a worm nursery, chuckl. My soil and compost are rather sandyish.

Earth worms like clay, I have clay soil and when I dug I found them, not organic stuff, that's for red wrigglers. That's been my experience.

Correct - earthworms are indeed not the same worms as one finds in their compost (though to be fair, ones' compost pile must be pretty poor and cool for worms to live there). Earthworms are a segmented burrowing worm whereas compost worms are generally the reddish surface dwellers. Earthworms do still rely on (mostly) dead organic matter. Thus, adding a good layer of organic matter as mulch will encourage earthworms and eventually better soil...better generally meaning improved soil structure.

I have both red wigglers and nightcrawlers in my compost piles. My piles heat up for a good while. During that time, the nightcrawlers go deep (usually do anyway) and the red wigglers migrate to the margins where it's cooler. When the heat subsides, the red wigglers occupy the first for our so while the nightcrawlers are usually deeper but make trips at our near the surface.

Worms don't have teeth and have small mouths. It's important to remember that. They require things to break down into extremely small particles, gel, and/or liquid. So large particles aren't eaten until they can actually be broken down by bacteria and fungi. That said, while I do put eggshells in my compost, the fact that they're mineral and large particles means I either have to powder them for them to be immediately usable or something else needs to make use of the shells first in order for them to be available to worms. I'm able to powder (actually more of a male texture after processing with my ninja) about 2/3 of my shells. The rest I do a quick crush with my rake but as them in larger pieces. My opossums and raccoons feed on larger eggshells anyway. Over time, large shells will process, but it takes years. I don't have any problem with considering large particles part of my long-term soil development.

Coffee grounds are fantastic both for worms and for black soldier fly larvae (BSFL). BSFL can process larger organic material with no problems. Some say BSFL make compost uninhabitable for worms. I can tell you that isn't true in compost piles They do process a lot of big stuff into small stuff and they do it quickly. In doing so, they create a really most environment around them. When they're in large numbers, the worms migrate to their edges. But eventually, they're back in all areas. BSFL do cause problems in worm bins that have limited area making it difficult for worms to migrate away from the high moisture caused by BSFL. I don't have that problem in compost piles. Anyway, IMHO you can't have enough coffee grounds (taking care to make sure the "browns" are available in correct proportions to allow for some hot composting. I use a LOT of coffee when I can source it (I don't drink it). My recent source fizzled out and I'm searching for one or more others.

I also get spent brewery grain, SCOBY and yes leavings from a local kombucha manufacturer, massive amounts of leaves (my browns), and eggshells from a local bakery. In fact, my eggshell pickup is today! I'm constantly looking for more safe inputs.

As you increase organic matter those worms will find you. Once you get them you'll need to assure a regular supply of organic material or most will move on once there is nothing left for them to eat.

I don't give my compost bin too much thought - just throw stuff in it as I get it - and always the egg shells and coffee grounds. Wrigglers like to use my bin for their nurseries. Have only turned it once or twice when it got cold and started to smell. I also empty my vacuum sweeper contents into it. I pick the charcoal out of my fireplace and add that too, to make a little bio-char.

Go to a bait store and get some angling worms , then put them in the hole with that potting soil, they will take it from there.

When it rains, I collect the worms off the sidewalk and street and add them to my bin, or rose garden. I figure they are going to dry up and die anyway, so it is a win-win situation for both me and the worms.