Nettle berry is found in Castle Anwyn near Wehnimer's Landing and removes a poison when eaten, similar to Unpoison (114). There is a nettle bush in the Kitchen Garden of Castle Anwyn at which GET BERRY will pick a berry.
There is a time check on picking berries that will prevent a single character from getting too many berries. For an unknown reason, having the berry in a container will prevent the container from being sold to the furrier or gemshop (in order to sell all the furs or gems in the container, respectively). It will return no messaging.
Getting another berry too soon may cause a minor hand wound:
You search through the brambles, but can't seem to find anything except some sharp thorns. Ouch!
Attempts after receiving a wound will be prevented:
You tentatively rub your hand. Remembering your last encounter with sharp thorns, you decide against another attempt right now.