which nasturtium is edible
Well Nasturtium is the genus name for the cresses, water cress, land cress etc. these are edible. The plant commonly called Nasturtium is Tropaeolum majus, and this is edible too, and tastes peppery of course, a little like watercress, which is why they called it nasturtium. There are a lot of Tropaeolum species, and I'm not at all sure that they are all edible. Some of them may indeed be poisonous.