Volatile Organic Compounds

Plants release a huge range of volatile organic compounds. The fresh-cut grass smell you link to summer lawns is actually a chemical distress signal — wounded grass gives off green leaf volatiles that attract wasps hunting the caterpillars doing the damage.

Sagebrush in the American West shows something even stranger. Neighboring plants that pick up airborne damage signals from clipped branches suffer noticeably less herbivore damage over the season that follows. The chemical warnings prime their defenses before attackers arrive — an early-warning system that travels through the air.