From Tolkien Gateway
The Fox by Anke Eißmann

Firs were Evergreen trees that grew across the northern parts of Middle-earth, and especially in the upper Vales of Anduin. On 23 September T.A. 3018[1] Frodo, Sam, and Pippin encountered firs at midnight in the Green Hill Country. The hobbits made a fire of fir sticks and cones and slept in angles between a great fir-tree's roots.[2]