I hope a little dissension is not objected to too vehemently. The earthworm, although often touted as the gardener's best friend, can also be a source of lots of problems, as it is actually an introduced invasive animal in North America. Check out http://ngm.nationalgeographic.com/2007/05/jamestown/charles-mann-text.html; National Geographic did an article on this little destructor a couple of years ago. I have read some stories of earthworm densities high enough they eat the living roots of the plants - you certainly do not want them in a pot or other enclosed garden. In addition, they break down organic matter much faster than the local native plants are used to, thus depriving them of a slow release of nutrients. I have plenty of them in my own garden, and let the birds and moles have their fill, hopefully keeping their numbers at a reasonable level. Moles are also good for eating lots of grubs that would otherwise eat the plants roots, so I leave them alone - it is the voles I do not like. So worms have many benefits, no doubt, but let us not take care of them too well, or spread them around, as they cause their share of damage, as well.