Are you sure they're not caterpillars? For caterpillars you could use bt, or put netting over you cabbages when they're little so the white cabbage butterfly can't lay eggs on them.

Here is a link that might be useful: White cabbage butterfly

Just for fun, try the old remedy of dusting your cabbage with plain old flour from the kitchen. If they are baby cabbage worms, then they will injest the flour, swell up and die.

Ok, if it is earthworms, then the next question is is there easy access between the cabbage head and the ground? Like really deep mulch piled around the stem? That might lead to them findy handy refuge in the heads because they can reach it so easily and/or if there is any rot or mold on the lower leaves it might wntice them to dine. In that case, pull the mulch furthe from the stems.

Or, are you having a wet spring? Then they could be hiding out to avoid drowning, I suppose.

Please, please, please post pictures.

I too have found baby earthworms in some of my cabbages which I picked yesterday. I am wondering if it is because of the extra water I put on the plants or because I did not take away the extra outer leaves. Be interesting to compare notes.

I too have had baby earthworms in my cabbage. It is gross to say the least when boiling cabbage. Has anyone found a solution to this? Thank you.

I too have earthworms in my cabbages and its gross will soaking in salt water get them out they are all through the heads

Yes I just discovered this in my cabbage I pulled out of my garden I was freaking out the only way I found out what it was was on a Japanese web page...I was scared they were parasites

I've found plenty of slugs hiding among the lower looser cabbage leaves but nary an earthworm. If I find earthworms in those looser leaves near the stem then they'd be up there hiding from the moles ;-)...or they are climbing up there trying not to drown in rain saturated soil as others have mentioned.

Maybe it's the variety of cabbage grown? Mine are all tightly packed hard heads that earthworms can't easily penetrate, other than the small gaps closest to the root/stem. Looser head varieties offer critters more places to hide. If I grew loose heads here we'd be dining on Slug & Cabbage stew......Yeah, I know this thread is old like me but I'm snowbound inside today, so what the hey.