“I am vertical/But I would rather be horizontal,” wrote Sylvia Plath, meditating on the consequences of a treelike existence. A team of researchers from the Vienna University of Technology recently announced another perspective on arboreal repose. Using sophisticated laser scanners they created images of trees during the night, when their metabolic processes slow down, and found that their branches had perceptibly drooped. They had “gone to sleep”, in the team’s words.
It is hardly a revelation: if your fluid pressure is reduced, you sag. What’s more interesting is the researchers’ language and their resorting to the ancient metaphor of “sleep”. Finding analogies between the physical forms and processes of trees and our own vertical life seems to be compulsive, a habit that goes back through Plath to the Romantic poets and beyond. We anthropomorphise them in a directly corporeal way. We talk of limbs and crowns and trunks. When a tree is felled we see a body, severed from its earthly roots and killed. Our empathy is understandable, and helps the world seem a more joined-up place, but it does a huge and damaging injustice to the tree world.
Vegetal existence is defined by immobility. Plants are rooted to the spot, which means they cannot escape predators or pursue sexual partners. To compensate they have evolved a modular structure and a range of senses and communication channels which far exceeds our own, and which includes sensitivity to magnetism, static electricity, low frequency sound waves and ultraviolet light. New understanding of plants’ abilities (and intelligence: they can learn, remember and change their behaviour as a result) means that they are beginning to be afforded the status of autonomous beings.