21. Eucalyptus
Eucalyptus trees are masters of chemical signaling.
When attacked by herbivores, they emit terpenes and other compounds that serve as warnings to neighboring eucalyptus.
These signals trigger nearby trees to boost their own defenses, reducing the risk of further attack.
Additionally, the chemicals released by eucalyptus can influence the growth of other plants in the vicinity, shaping the plant community around them.
Source