Thank you. The rabbits and I are of one mind, in that case. Years ago we read that it was used as a vegetable by Medieval monks so we thought we'd try it. Once was enough for me.
Ground elder is very similar to Cow parsley, which IS safe for piggies. Cow parsley has very smooth clean green stems, where-as ground elder has stems which have purple stains and hairs on them. There is a good article that shows the difference in a recent issue of Guinea Pig magazine. Basically, if you are not sure if a weed is safe for piggies, don't risk it.
But I have never given mine Cow parsley either!
Thank you for the advice. I have given a few bits of Dock within a foraged from the garden salad - Marjoram, Mint, Dandelion, Thyme, Sage, grass. I also feed a few Raspberry leaves as we have rampant, very old Rasps which never produce much fruit and what there is is taken by the birds.
Still on the subject of weeds, has anyone fed Dock leaves to your piggies? I have read in one or two books that they CAN eat it. I have never tried mine with it as It just doesn't look very nice to me!
@parkdaleangela, Hi! 
The article is in issue 24 of GPM. I don't know if Ground elder is safe for piggies to eat. I wouldn't risk it. Cow parsley flowers do come in different colours and the stalks are always clean green and covered in fine hairs. Hemlock has smooth stalks with blotchy purple markings and flowers are always white. As with any wild plants or weeds, if in doubt, leave it out! 