Pipe-weed (also known as Halflings' Leaf) is a strain, likely of nicotiana, grown and enjoyed much by the hobbits of the Shire, to whom it was first introduced by Tobold Hornblower. Pipe-weed production is a major industry there, especially in the south. It was known among the Dúnedain as sweet galenas for its fragrance. In Gondor it grows as a wild plant, appreciated primarily for its sweet-scented leaves.
In Gondor, it is known popularly as Westman's-weed, a reference to its origin: it was apparently brought to Middle-earth by Númenóreans during the Second Age. It was first grown among hobbits by Tobold Hornblower in Longbottom (a region in the Shire) around S.R. 1070 (TA 2670). Despite its foreign origins, the hobbits (possibly those in Bree) were the first to use it for smoking.
Popular varieties of pipe-weed include Longbottom Leaf, Old Toby (which is named after Tobold Hornblower), Southern Star, and Southlinch, which is grown in Bree.The Wizard Gandalf learned to smoke pipe-weed from the hobbits and is known to blow elaborate smoke-rings. Saruman initially derides him for this, but at some point he takes up smoking himself. After the destruction of Isengard, pipe-weed is found among its stores, but the hobbits Merry and Pippin fail to realize the sinister implications of the discovery that Saruman has had commerce with the Shire.