I have heard mixed info on harvesting nettles (Urtica dioica). Some sources say to only eat the leaves of young plants because as they get older and once the plant flowers they can be harmful.

However, it seems to be claimed it is due to calcium carbonate deposits in the plant, other sources mention there is no evidence these are harmful and also wouldn't stomach acid dissolve them pretty quickly anyway?

I am curious if anyone has tried and noticed any problems from eating large quantities of mature leaves, especially cooked ones. I have a massive source of them and it would be nice to make use of them.