Super-sonic plants
From The Stargate Omnipedia
Flora on PJ2-445 which emit an extremely low level of sound essential to maintaining a species of sound-sensitive aliens that co-exist with them on the planet. The plants appear in clusters on the surface, with brilliant pink blooms -- but underground they are networked together as essentially one giant organism.
If a plant becomes physically damaged the sound quality is changed, which profoundly affects all connecting plants in the network, as well as the intelligent life forms. One change in their environment can effect life for kilometers around, and perhaps more.
KEY EPISODE
One False Step - A U.A.V. crashes into the flora on PJ2-445, in turn causing the local population to begin falling ill.