Secret Behind the Smell of Freshly Cut Grass

Have you ever wondered why freshly cut grass smells so good? Many people enjoy the aroma of a newly mowed lawn, golf course, or baseball field, but few know the reason behind it. The truth is, the smell of freshly cut grass is actually a chemical distress call that plants release when damaged. The smell is caused by the release of volatile organic molecules like esters and aldehydes. The aroma is a mixture of organic compounds called green leaf volatiles (GLVs) that serve as an aromatic distress signal to surrounding vegetation. 

The purpose of GLVs is to alert other plants of imminent danger and to trigger various defensive responses. Some of the compounds stimulate the formation of new cells at the wound site so it closes faster. Others act as antibiotics that prevent bacterial infection and inhibit fungal growth. A few spur the production of defensive compounds at un-wounded sites as sort of a pre-emptive fortification. And still others react with other chemicals to act as something like distress signals

One of the most fascinating aspects of GLVs is that they can also attract beneficial insects to the rescue. Scientists have found that the saliva of certain caterpillars reacts with the GLVs released by coyote tobacco plants to make them attractive to the "big-eyed bugs" that regularly eat the caterpillars⁴. This way, the plants use their enemies' enemies as allies in their defense. Other examples of insect-plant interactions mediated by GLVs include attracting parasitic wasps, predatory mites, and ladybugs

The smell of freshly cut grass may seem pleasant to us, but it is actually a sign of plant stress and trauma. It is also a complex communication system that involves plant-plant and plant-insect interactions. The next time you smell freshly cut grass, remember that you are witnessing a chemical warfare between plants and herbivores, and a mutualistic relationship between plants and insects.