In his famous 1845 essay Walden, philosopher Henry David Thoreau wrote how life would "stagnate if it were not for the unexplored forests and meadows."
"We need the tonic of wildness," he wrote. "We can never have enough of nature."
Ninety-three years later, Sierra Club founder John Muir's words embraced trees as an aspect of nature that provides America its serenity and hope.
"The clearest way into the Universe is through a forest wilderness," Mr. Muir was quoted as having written in John of the Mountains: The Unpublished Journals of John Muir .
Americans are especially sentimental about trees this time of year because of Arbor Day, which was observed Friday.
But go to virtually any moment in history.
Great writers, philosophers, and inspirational figures can undoubtedly be found making earthly connections between the human race's affection for trees and its need for spiritual nourishment.
People need air. They need water. Some people claim society's inherent need for trees is almost as fundamental.
Others weigh our scientific need for trees against our practical emotion for them.
But no matter how much logging Americans tolerate and no matter how wide their ethics may be divided over the use of nature's resources, nobody ever seems to fathom - or come close to advocating - the idea of a treeless society.
The notion of flattening parks and taking away shade would make most people wince.
Yet, ironically, Arbor Day's roots aren't traced back to the fall colors of Mr. Thoreau's New England or the majestic redwoods of Mr. Muir's California.
The idea came from a westward pioneer from Detroit named J. Sterling Morton.
When Mr. Morton and his wife, both nature lovers, settled in the Nebraska Territory in 1854 they were dismayed by the lack of trees.
The state now known as Nebraska was, at the time, a treeless plain.
"There is no aristocracy in trees," Mr. Morton once said. "They are not haughty. They will thrive near the humblest cabin just as well as they will in the shadow of a king's palace. There is a true triumph in the unswerving integrity and genuine democracy of trees."
Mr. Morton founded Arbor Day on April 22, 1885, to promote tree-planting.
States have observed the event in various ways ever since.
It has been observed nationally for years on the last Friday of April.