Vincent Van Gogh once wrote “What a simple thing death is, just as simple as the falling of an autumn leaf.”
The Dutch artist, like many people, apparently equated falling leaves with death, but the process of leaves falling is anything but simple. But it is absolutely necessary for the life of a deciduous tree.
For years, I had been taught, and it is true, that trees lose their leaves to protect themselves from damaging wind and snow. But more importantly, deciduous trees lose their leaves so they can survive the winter.
Tree leaves are tender, thin and filled with a watery sap. Suppose our trees retained the same leaves year after year. Even if leaves went into dormancy in autumn, during January thaws and false springs, they would resume the process of photosynthesis, and with the inevitable temperature drop, the tender leaves would freeze. Consequently, the tree would be without sustenance and very quickly die.
Therefore, trees have evolved a complicated process of each summer, developing tough weather-resistant leaf buds for the coming year, and then in early fall, absorbing and storing the nitrogen and valuable minerals it will need to sustain itself in future years.
The process in which the trees then discards leaves is anything but simple. Essentially, after the tree absorbs the nutrients, protective corky cell layers form in each leaf stalk, cutting off the leaf from the tree. The top layers are quite weak, so when the bottom layers expand in autumn, they sort of push the leaves off the tree.
Wind helps.
The trees absorb nutrients, then discard their spent leaves to sustain themselves. In doing so, the whole forest benefits.
Shed leaves restore soil nutrients and as they decompose, they make up part of the spongy humus layer of the forest floor that absorbs and holds rainfall while providing the carbohydrates for soil organisms that are so vital to the forest ecosystem.
It’s kind of like public radio. Each autumn, about this time each year, it absorbs the funds necessary to sustain the station, but in doing so, the whole listening community benefits.
