Why Does Fresh Cut Grass Smell That Way?

There’s more behind the smell of freshly cut grass other than it is a pleasant aroma to most people. The scent is actually the plant giving out its own distress signal that something has gone terribly wrong. But who is the grass signaling to? It may be letting insects know it needs some help.

After a lawnmower runs over grass and chops it down, the grass releases chemicals called green leaf volatiles in response to the injury. Green leaf volatiles, which are found in most leafy plants, act as a defense mechanism to keep pests away or make the plant less attractive to pests when it is damaged. These chemicals can protect the plant from fungi and bacteria growth and can act to prevent future damage by encouraging new growth.

There is another compound that is released by the plant during an assault called jasmonic acid. This compound is thought to deter plant-eating insects while signaling beneficial insects to come to the plant’s aid. Researchers at Texas A&M University found that parasitic wasps were attracted to green leaf volatiles and would lay eggs in the insects trying to eat the plant. This was a way for the plant to save itself from further damage.

But what actually gives grass that distinctive odor almost everyone is familiar with? One of the compounds that is released after grass is cut is called cis-3-hexenal. It’s…