Cress

A short-stemmed green plant that grows rapidly in watery conditions, often found along the edges of streams and pools, for which reason it is sometimes also known as 'watercress'. It is only specifically mentioned as growing by a stream that ran down from Emyn Muil into the Entwash Vale, though it was doubtless found beside watercourses across Middle-earth.

Early editions of The Lord of the Rings also included a mistaken second reference to cress, growing among the flowers of Bilbo Baggins' garden at Bag End. Tolkien had written of nasturtians - brightly coloured flowers quite unrelated to cress - in the Bag End garden, but this was wrongly amended to nasturtiums by a proofreader. Nasturtium is properly a reference to cress, and this reference was corrected in later editions to Tolkien's intended reading of nasturtian.

This situation is complicated by the fact that common usage has shifted since Tolkien wrote The Lord of the Rings and, despite the fact that they are quite unrelated to one another, nasturtium is now commonly used for both kinds of plant. (Presumably this shift in usage is due to the same kind of false assumption made by the original proofreader of The Lord of the Rings.)