The smell of freshly mown grass that many gardeners find so appealing is actually caused by volatile organic compounds (VOCs) released from shorn leaves in order to notify its neighbors that they are under attack. In nature, the grass releases these compounds when it’s a victim of an insect pest or a grazing mammal. Thus it warns neighboring grasses of an eminent attack and they can start preparing themselves by producing deterrents: toxic compounds or unpleasant tastes to ward off predators.
In addition, certain compounds emitted by mown grass stimulate the formation of new cells on the wound so it closes more rapidly. Still others act as antibiotics to prevent outbreaks of bacteria and fungi. Some VOCs also attract beneficial insects such as parasitic wasps and predatory bugs, which come in expecting to find their prey, a plant-eating caterpillar, chewing on the leaves.
So mowing the lawn products a multitude of different effects, both in the grasses that are being sheared, in other grasses in the vicinity and even in nearby insects. That’s quite a chain reaction when all you thought you were doing was reducing the height of your lawn!
No doubt, in time, turf grasses will evolve and learn to emit foul odors or toxic fumes when being mowed in order to discourage human beings from touching them. You have been forewarned!