If you add lots of humus and good organic compost the worms will arrive ny themselves - you can't introduce them.

Dave, you've asked a similar question before - and got the same answer. Go to the garden centre and get some good soil conditioning material, such as composted animal manure or just soil conditioning compost.

MG and B are right. When I came to this garden I had nothing but stones and clay and not a worm in sight. After digging in lots of compost and manure, I soon had worms everywhere. It really does happen. Where do they come from? Now, that I can't answer!

I'd add this just to try to convince you - if you have a shortage of worms in your soil currently, then its either bone dry, or more likely, the soil is impoverished and is an inhospitable environment for worms. If you were able to import earthworms and add them to the soil, they'd soon disappear, either because they'll die or just shove off elsewhere, it'd be like putting fish in a fish tank without any water. Improve the soil, and the worms will arrive.

When we took on the area where we grow vegetables there was nary a worm to be seen the soil was so poor and impoverished now you put a fork in anywhere and there a wonderful big fat juicy worms.