What causes the smell of freshly cut grass?
Quick answer
The smell of freshly cut grass comes from chemicals called green leaf volatiles (GLVs), released when grass leaves are damaged. The main ones include (Z)-3-hexenal, also called cis-3-hexenal, which gives the sharp “green” smell, and related compounds such as hexenol. For the plant, it’s essentially a distress signal and a quick defense.
How the smell is made
| Step | What happens |
|---|---|
| Cutting | Mowing breaks open leaf cells |
| Enzymes | Enzymes act on fats in the cell membranes |
| Release | Green leaf volatiles form within seconds and drift into the air |
| Change | The compounds quickly change into others, so the smell shifts over a few minutes |
That’s why the smell is strongest right after mowing.
Why grass does it
Scientists think green leaf volatiles help plants in several ways:
- Antimicrobial: protect the wound from bacteria and fungi
- Defense: may deter some plant-eating insects
- Calling for help: attract predatory insects and parasitic wasps that attack caterpillars eating the plant
- Warning neighbors: nearby plants may detect the chemicals and strengthen their own defenses
In other words, the pleasant summer smell is the plant’s emergency response.
Why do people like it?
Many people find the smell refreshing and linked to happy memories of summer. Researchers have even studied whether green leaf volatiles have a calming effect. The smell is used in perfumes, air fresheners and to add “fresh” notes to food flavors.
Not only grass
Green leaf volatiles are released by many plants. They contribute to the smell of tomato leaves, the fresh scent of crushed leaves and the “green” taste of some fruits and vegetables, such as unripe apples.
Related smells in nature
| Smell | Cause |
|---|---|
| Cut grass | Green leaf volatiles |
| After rain | Geosmin and plant oils; see what causes the smell after rain |
| Sea air | Dimethyl sulfide from plankton |
| Pine forests | Terpenes like pinene |
For another plant chemistry question, see why leaves change color.
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