According to this website, fresh cut grass is one of the best smells to us humans. Living in Maine, the smell of cut grass is one of the many things that signal the coming of the best week of the year, summer. But why is it that grass smells the way that it does when it is cut?
All green vegetation produces chemicals called green leaf volatiles (GLVs). GLVs are a major form of communication between individuals and even possess some level of antimicrobial properties used to prevent infection. I’m sure that you see where this is going.
When grass is mowed, the distinctive odor you smell is actually the extreme production of GLVs. These GLVs are sent out as a distress signal to neighboring plants, warning them of imminent danger. This allows the neighboring grasses to enter into a sort of state of defense, priming them for the attack. Some studies have shown that the GLVs also serve to alert and attract predators to ward of the herbivores. In a nutshell, what you are smelling is the tortured outcry of thousands of individuals (that sounds intense).
A study that was done by Northwestern University found that parasitic wasps were attracted to plants emitting GLVs in response to herbivorous insects, effectively scaring off the herbivores. Another study found that orchids released pheromones along with the GLVs, attracting wasps for both defense AND pollination. It really is cool what plants can do.
Perhaps the most beneficial trait of GLVs is the ability to prevent infection at the site of injury. Essentially, the GLVs are able to make the plant more resistant to bacterial or fungal infections. It isn’t that dissimilar to how our own bodies work in developing scabs. Actually, it is probably very different. But if it helps to picture a scab, go for it.
So the smell of cut grass is actually a warning signal to other plants, evidence of self healing, and a way to attract predators of the herbivores that dare attack them. Pretty intense stuff when you think about it. It is my belief that we have barely scratched the surface of what plants are capable of. If you think about it, it wasn’t until a few decades ago that we acknowledged that animals could possess any level of consciousness (shout out to Jane Goodall for her work), and it hasn’t been until very recently that substantial research has been done on plants. I have found papers suggesting the ability for plants to learn and hear, and the reality that trees work together in a forest to survive. The future is exciting in the world of plant biology.
Brodmann, Jennifer; Twele, Robert; Francke, Wittko; Hölzler, Gerald; Zhang, Qing-He; Ayasse, Manfred (2008-05-20). “Orchids Mimic Green-Leaf Volatiles to Attract Prey-Hunting Wasps for Pollination”. Current Biology. 18 (10): 740–744.