Pipe-weed (also known as Halflings’ Leaf or simply Leaf) was a plant developed by the Hobbits of the Shire.
The Leaf was famous for its fragrant flowers. It preferred southern climates and it grew abundantly in Gondor. In northern regions, like Eriador, it was not as rich and large, and never found wild; it flourished only in warm sheltered places like the southern slopes of the Bree-hill, or Longbottom of the Shire. 
Apparently the plant grew in Númenor and was brought to Middle-earth by Númenóreans during the Second Age. In Gondor it grew as a wild herb, appreciated primarily for its fragrant blossoms and the Gondorians knew it as sweet galenas or more popularly as westmansweed,  a reference to its origin.
It was not until the Third Age when it reached Eriador, probably through the Greenway, and the Bree-hobbits were the first to put it in pipes and use it for smoking. As Bree was an ancient cross-road, the habit of smoking pipe-weed spread to other regions, as well as to other races, such as Men, Dwarves and Wizards. Meriadoc Brandybuck considered The Prancing Pony as the “home and centre” of the smoking art. 
But it was in the Shire where it was first domesticated, by Tobold Hornblower of Longbottom in Southfarthing around S.R. 1070. The cultivation and exportation of this herb became a key industry in the Shire, especially in the south. Popular varieties of pipe-weed included Longbottom Leaf, Old Toby, and Southern Star from the Shire.  Perhaps less popular was Southlinch from Bree. 
The Wizard Gandalf learned to smoke pipe-weed from the Hobbits and was often seen blowing smoke-rings.  Saruman initially derided him for this, but at some point he took up smoking himself, and even had commerce with the Shire: After the destruction of Isengard, pipe-weed was found among its stores, but the Hobbits Merry and Pippin failed to realize the sinister implications.
After the War of the Ring, Meriadoc Brandybuck authored Herblore of the Shire discussing the origins and history of the Hobbits’ ‘art’ of smoking Pipe-weed. 
In the prologue to The Lord of the Rings, Tolkien stated specifically that “it is a strain of the herb nicotiana“,  i.e. tobacco.
The common Gondorian name of pipe-weed was Westmansweed.  The more noble name was galenas (a Númenórean Sindarin form of the proper Sindarin form galanes), with Quenya forms alanesse or alenesse derived from ala- “plant, grow” and nes- “sweet smelling”. 
 Portrayal in adaptations
The smoke from Sweet Galenas takes the form of a sailing ship that floats out from the pipe.
The plant is used for healing Tallion, as well as other plants.
Pipe-weed Pipe-weed (also known as Halflings’ Leaf or simply Leaf) was a plant developed by the Hobbits of the Shire. Contents  Properties The Leaf was famous for its fragrant