We already have Mountain-root, yet here is the humble component. Four of these seven refer to the roots of mountains rather than trees (and none to simple grass). I am fascinated.
• 3.010 Bilbo’s pony began to stumble over roots
• 5.012 down at the very roots of the mountain.
• 5.026 What has roots as nobody sees,
• 8.030 his hands slipping off the slimy roots at the edge,
• 9.059 and there for a while they stuck against some hidden root.
• 12.012 right at the Mountain’s root.
• 12.096 beneath the roots of the Mountain,