Tu Bishvat, the Jewish Arbor Day is a call against "plant blindness". When I say "plant blindness", I'm not referring to a plant's visual acuity. Plants are anything but blind. While plants may not see in pictures like you or me, they are acutely aware of the surrounding light in their environments. Plants discern between blue and red light, and use this information to know which direction to grow. Your plants on the windowsill bend to the sunlight so that they can absorb the light needed for photosynthesis, the energy-producing metabolism of the plant. Plants actually know how to measure the length of the night, the period between sunset and sunrise. Plants differentiate between the ever-dimming scarlet light of sunset, and the brightening orange light of sunrise, and use this information to determine when to flower.
"Plant blindness" relates less to the plants' abilities, as it does to ours: we are often blind to plants.
That's not to say that we don't see plants. We see them all around us: Arazim and Orenim in the forest, grass in our lawns, shkadia blossoms in harei jerusalem, and rakafot and calaniot in the field. We see miles of wheat fields as we drive south on Route 6. While we see plants as passive objects in our visual landscape, we are blind to their complexity. The static plant world we experience belies a dynamic plant community that includes perception, communication and complex information processing.
Why are we blind to the complexity of the plant world? First, plant movements, with the noted exception of a few rapid movers such as the Venus Fly Trap, occur over long timeframes – too slow for our impatient eyes. Leaves slowly move up and down in response to changes in temperature and light; stems dance in various shapes ranging from circles to figure 8s, but only over a course of several hours, so that only though time-lapse photography do we discern these purposeful motions that characterize the plant world.
Second, we see only half of the plant world – the stems, leaves and flowers. Underground, the other half of the plant world, the roots, are continuously exploring, probing the soil for nutrients, signs of water, and differentiating between friend and foe. The roots of some species are so advanced that they grow away from their cousins, but will grow over, and steal resources from roots of another species!
So to combat plant blindness in humans, we have to learn to appreciate the complexity we can't see. We need to learn to see the beauty in the thousands of meticulous scientific studies which have elucidated the ways plants sense their environment, whether by seeing light, or smelling their neighbors, or listening to insects.
And why should plants be so complex in their abilities to sense the environment? To survive. As opposed to us, plants are literally rooted in one place. They can't escape their environment. Humans and other animals respond to hostile environments by running away, by seeking out more hospitable conditions. Plants can't run away from stress. Held in place, they must suffer extreme changes in temperature, drought and flooding, strong winds, and insect infestations. Their survival is not based on the ability to escape, but rather to adapt. Thus plants have to be very aware of changes in their environment so that they can quickly respond and survive.
Yes plants are acutely aware of the world around them. They are aware of their visual environment. They are aware of aromas surrounding them and respond to minute quantities of volatile compounds wafting in the air. Plants know when they are being touched and they are aware of gravity – they can change their shapes to ensure that shoots grow up and roots grow down. And plants are aware of their past – they remember past infections and the conditions they’ve weathered, and then modify their current physiology based on these memories. And most importantly they integrate all this diverse information to yield a plant exquisitely adapted to its current environment.
We need to appreciate a plants' complexity, because there is one more thing we are blind to when it comes to plants - We are blind to our dependence on them. We wake up in our house made of wood from the forests of Maine, pour a cup of coffee brewed from the coffee beans grown in Brazil, throw on a tee-shirt made of Indian cotton, and eat a locally-sourced tomato and cucumber salad, with toast made from wheat grown in Kansas. We drive our kids to school in a car with tires made of rubber that was grown in Africa and fueled by gasoline derived from Cycad trees that died millions of years ago. Chemicals extracted from plants can cure cancer and reduce fever, or increase our appetite, calm our nerves or block pain. And most importantly, we breathe the oxygen produced by plants worldwide.
Our existence is totally dependent on ensuring the continuation of plant life on Earth. So doesn't it behoove us thie Tu B'shvat to be a bit more appreciative of plants? To truly see them for what they are – complex and amazing organisms which not only make us happy to look at, but which provide us with the gift of life.