The long season of dormancy is officially broken: I walked into our production greenhouses this morning and noticed a wonderful change in the air…I could smell the plants growing! Although not a single green leaf adorned any of the shrubbery starts that were being overwintered in the greenhouse, I could confidently surmise that good things were happening in the soil and that greenhouse life had woken up on the farm. After a quick walk through the greenhouses, I went back to my kids at breakfast table and told them the great news.
“Bah,” one of my kids said as he rolled his eyes, “how can anyone possibly smell plants growing?” Good question! Having been a greenhouse grower for almost half of my life, I too had to ask myself how it was that I seemed to possess an ability to sense a change in the biology of plants without actually seeing anything. Did the existence of this ‘farmer’s nose” really have any basis in reality, or was it just wishful thinking? And what about all of the stories of other farmers smelling their crops, were they just a bunch of wives’ tales too? I sat down at the phone and the computer, did an afternoon of research, and here’s what I found out…
1) The Farmer’s Nose, otherwise defined as the uncanny ability to smell changes in the air, is real. But it is not limited to farmers, everyone has it (farmers are just more attuned to smelling their way around.) Human beings have been shown to smell changes in the atmosphere produced by several substances, in quantities as low as a few parts per quadrillion. So much for the idea that the only valuable thing we use our noses for is to hold up our reading glasses.
2) “The smell of plants growing” can be more accurately defined as “the smell of the earth growing things.” Turns out there is a compound called geosmin that is released into the soil as certain types of earth-dwelling algae and bacteria finish their life cycle (geosmin also occurs in water). When there is a disturbance to the soil via wind, water, or movement, the geosmin volatizes (turns to gas) and becomes available to our olfactory bulbs for processing. Chemically known as bicyclic alcohol, geosmin can be detected by human beings at the tiniest concentration levels of 5-10 parts per trillion of atmospheric air.
3) Geosmin is widespread around the world and our ability to sense its presence has helped the human species survive the past several tens of thousands of years. Often being stirred up / volatized as a result of increased moisture content in soil (i.e. the presence of a stream), scientists have speculated that ancient travelling and nomadic peoples relied on the ability to smell this compound in order to lead them to water. The food we eat is also subject to geosmin flavoring: root veggies such as potatoes and beets owe part of their distinctive taste to geosmin; fish absorb geosmin from sources such as lake and river bottoms. (Chef’s note: if the fish you are preparing smells too pungent, it is a result of an increased level of geosmin in the fish. Simply prepare with acidic sauces such as lemon juice or vinegar to neutralize and remove odor.)
In all, I am happy to report that today was a great day, both for awaiting the warm sun and gorgeous greenery that spring provides, and also for discovering yet another interesting and intricate part of human biology. Serving to both aid in our future evolutionary success and to connect us to our ancient past, it seems that geosmin is delicately intertwined with the human experience!