The Old Forest is a small forested area which lies east of the Shire.
The Old Forest is one of the few survivors of the primordial forests which covered most of Eriador before the Second Age, and it once was but the northern edge of one immense forest which reached all the way to Fangorn Forest.
The Hobbits believed the trees of the Old Forest were in some manner 'awake', and were hostile. They sway when there is no wind, whisper at night, and mislead travellers deeper into the forest. When the trees grew too close to the hedge, hobbits cut down the trees nearest and created a clearing by a bonfire. Ever since then, the trees were more hostile.
It is probable that some trees of the Old Forest were Huorns.