Art is the Tree of Life. Science is the Tree of Death.

Astrology is a sickness, not a science ... It is a tree under the shade of which all sorts of superstitions thrive.

Gravity is only the bark of wisdom's tree, but it preserves it.

He that plants trees, loves others besides himself.

I return to the newborn world, and the soft-soil fields,
What their first birthing lifted to the shores
Of light, and trusted to the wayward winds.
First the Earth gave the shimmer of greenery
And grasses to deck the hills; then over the meadows
The flowering fields are bright with the color of springtime,
And for all the trees that shoot into the air.

I saw them; there is nothing beautiful about them, just that they are a little higher than the others.
Referring to one of the oldest and loveliest groves of redwoods, showing insensitivity to their magnificence.

I think, too, that we've got to recognize that where the preservation of a natural resource like the redwoods is concerned, that there is a common sense limit. I mean, if you've looked at a hundred thousand acres or so of trees—you know, a tree is a tree, how many more do you need to look at?
Opposing expansion of Redwood National Park.

If some race of quadrumanous animals, especially one of the most perfect of them, were to lose, by force of circumstances or some other cause, the habit of climbing trees and grasping the branches with its feet in the same way as with its hands, in order to hold on to them; and if the individuals of this race were forced for a series of generations to use their feet only for walking, and to give up using their hands like feet; there is no doubt, according to the observations detailed in the preceding chapter, that these quadrumanous animals would at length be transformed into bimanous, and that the thumbs on their feet would cease to be separated from the other digits, when they only used their feet for walking.

Is not disease the rule of existence? There is not a lily pad floating on the river but has been riddled by insects. Almost every shrub and tree has its gall, oftentimes esteemed its chief ornament and hardly to be distinguished from the fruit. If misery loves company, misery has company enough. Now, at midsummer, find me a perfect leaf or fruit.

It is interesting to observe the result of habit in the peculiar shape and size of the giraffe (Camelo-pardalis): this animal, the largest of the mammals, is known to live in the interior of Africa in places where the soil is nearly always arid and barren, so that it is obliged to browse on the leaves on the trees and to make constant efforts to reach them. From this habit long maintained in all its race, it has resulted that the animal's fore-legs have become longer than its hind legs, and that its neck is lengthened to such a degree that the giraffe, without standing up on its hind legs, attains a height of six metres (nearly 20 feet).

It’s very dangerous to invent something in our times; ostentatious men of the other world, who are hostile to innovations, roam about angrily. To live in peace, one has to stay away from innovations and new ideas. Innovations, like trees, attract the most destructive lightnings to themselves.

O leave this barren spot to me!
Spare, woodman, spare the beechen tree.

Sir Edward has calculated that quick-growing Indian eucalyptus trees have a yield of nine and one-quarter tons of wood an acre a year. As the wood contains 0.8 per cent of the solar energy reaching the ground in the tropics in the form of heat, Sir Edward has suggested that in theory eucalyptus forests could provide a perpetual source of fuel. He has said that by rotational tree planting and felling, a forest of twenty kilometers square would enable a wood consuming power station to provide 10,000 kilowatts of power.

The improvement of forest trees is the work of centuries. So much more the reason for beginning now.

The time has come to link ecology to economic and human development. When you have seen one ant, one bird, one tree, you have not seen them all. What is happening to the rain forests of Madagascar and Brazil will affect us all.

Trees and fields tell me nothing: men are my teachers.

Why is geometry often described as cold and dry? One reason lies in its inability to describe the shape of a cloud, a mountain, a coastline, or a tree. Clouds are not spheres, mountains are not cones, coastlines are not circles, and bark is not smooth, nor does lightning travel in a straight line... Nature exhibits not simply a higher degree but an altogether different level of complexity.

[Science] is the literature of God written on the stars—the trees—the rocks—and more important because [of] its marked utilitarian character.