If you keep adding organic matter to the soil you will get worms naturally. I don't think introduced worms will survive if conditions are not to their liking.

Be patient and add as much OM as you can find.

Marshall

Aha...something I know a little about.

While, yes, worms are very good for the soil; they are usually an indicator of improved soil. marshall2000 is right. Keep adding organic matter and the worms will come. Remember they like bacteria so you'll want to incorporate as much green matter as possible. Green compost items=bacteria food, brown=fungi food (and bacterial food but to a lesser degree, the bacteria need the fungi to break it down for them to eat).

By creating a bacterial rich environment it will attract all the food your local worms will enjoy. They'll be coming back for seconds and thirds.

Greenjeans

I agree that if you add enough organic matter, you'll get worms. Be open to any kind of organic matter you can get, organic waste from any manufacturing, food processing, etc. If your ground is really devoid of worms, it probably wouldn't hurt to get some soil from your neighbors that has worms in it to seed your now enhanced soil.

The correct worm for the garden are the earth worm and not the compost worms. Just keep adding the OM to your garden. Would help if you can add some manure as well. And BTW, keep the area well watered. Give it time and as the OM in the soil increased, so will the worms