OAK: Strength, solidity, durability are symbolized in the Oak. The tree is connected with the traditions of the race, and it is associated with literature. It is a tree of strong individuality, with bold, free growth and massive framework. Its longevity appeals to every person, even though he has no feeling for trees. It connects the present with the past. It spans the centuries.
This feeling that the Oak represents a long span of years is itself the reason why we should consider the tree with veneration and let it live its full time; and this is the particular lesson which the writer would impress. Spare the isolated Oak trees! Of whatever kind or species, a mature Oak is beyond price. To allow it to remain bespeaks culture and kindly feeling.
-L.H. Bailey, Cyclopedia of American Horticulture