old tree; ancient tree
Refers to a tree that has lived for many years, often with a sense of dignity or venerability.
神社の境内には老い木が立っている。
An old tree stands in the shrine grounds.
その老い
That ancient tree is said to be several hundred years old.
Compound of 老い (oi, 'old age') + 木 (ki, 'tree'). The reading おいき is a straightforward combination.