Lindens

No linden tree is directly described anywhere in Tolkien's tales, but we have enough indirect references to show that they were widely known. Two of these references come from poems associating them metaphorically with Lúthien of Doriath and with Nimrodel of Lórien (though strictly speaking this shows only that the trees were known to the authors of those poems, not that they necessarily grew in those places). We also have a description of an Ent in Fangorn Forest who had the appearance of a linden tree, which is rather stronger evidence that lindens could be found in Fangorn, but still not quite conclusive.

There are two main species of linden found in western Europe (and hence the northwest of Middle-earth): the little-leaved linden Tilia cordata and the large-leaved linden Tilia platyphyllus. As Tolkien describes linden leaves as being proverbially light, it seems that it must have been the more common little-leaved variety that he had in mind.

Specifically, the name linden derives from Old English lind, and ultimately from a hypothesised Proto-Indo-European root *lent, meaning 'flexible'. This is also the source of the English word lithe, and of the tree's rarer alternative name of lime (which is somewhat confusing, as lindens have no connection with the fruit of the same name).