True Dirt

red states

In November the garden enters an altered state. The angle of light shifts leaving the yard in shadow where flower borders and ground dwelling plants have gone to seed or rest for the season. But up above in the garden canopy a transformation is occuring--the trees and clambering vines that during the growing months provide a subtle backdrop of greens have suddenly taken the stage in brilliant array. This year it is an extravaganza of reds. The scarlet oak reveals its dual nature for one month of the year, beginnning with the far edge of the furthest leaf on the longest limb of the towering tree. A glowing edge becomes a neon sign and finally the whole bower combusts. The fire dies out quickly to a dull doe brown where only the embers of heat remain in the leaf's inner vein.

The dying of the light and the leaf are intertwined in the deciduous trees of the temperate zones. The longer night, it seems, is the cause. And yet, some aspects of this transformative act are probably etched in the genes of the leaf. Some will change even without the signaling long-dark periods.

Have you ever asked why the leaves turn? I confess to not having once thought about it in all my years of leaf viewing. We (the scientists, that is) know only that a green leaf is green because it is packed with cells whose only job is to turn sunlight into food (or chlorophyll) for the tree. The leaf turns to yellow at the end of its annual cycle--when it is worn out from its chlorophyll production tasks. But a leaf turning from green to scarlet is something different. Red pigment must be created by the leaf, and it uses up valuable energy when doing so. Only some trees paint themselves red in the fall but we don't know why. Recently, it has been speculated by plant geneticists that the red pigment is a deterent to insects that might want to eat the leaf, or lay their eggs on it. The red signals poison to them. But plant physiologists have come up with a competing theory for autumn reds--sunscreen. The red pigment apparently acts as a sponge for dangerous free radicals that can burn the leaf.

Whatever their reasons for turning red, the scarlet oak and the Japanese maple in my garden are just doing what all their species do each year. The wild grape, on the other hand is a mutant and can't be held accountable to its cousin species. A local plantsman of note, Roger Raiche, found the differently-colored grape somewhere in the hills of the East Bay. The species normally turns from green to golden yellow in the fall. Roger's grape decided red was better. Now it is commonly seen about the town, draped over trellises and consuming lesser shrubbery and small structures. Roger's Red, the nurseries call it.

Posted by briggs at December 2, 2004 3:01 PM | TrackBack