The Organic Gardeners: Plants Can Talk!

  • This hibiscus plant is covered with aphids. Is it calling out for help? Photo: Doug Oster

June 28, 2013

The scientific community has known for about 20 or 30 years that plants can communicate with each other. They don’t do it the same way that humans do, though.  These plants accomplish their communications with a class of volatile chemicals called semiochemicals, which are released by the plant in response to stress.

For example, in times of drought, a suffering plant will emit semiochemicals into the air that alert other plants of its plight.  The receiving plants will close their stomates, or the pores in their leaves, to prevent moisture loss.

"It's as if they are saying, 'Hey, I’m getting a signal from my neighbor that says he’s suffering from drought, so I prevent as much moisture loss from myself,'" says Jessica Walliser(the other half of The Organic Gardeners).

These signals aren’t only for drought.  Plants can warn other nearby plants of insect invaders, giving these plants a chance to build up chemical defenses to sour leaves. Some classes of semiochemicals allow the plant to communicate with beneficial insects.  For example, when a plant is being attacked by an herbivore, or insect pest, it releases a particular class of chemicals known as Herbivore Plant Induced Volatile, or HPIV. These are actually released by the plant as an S.O.S. signal.  They are calling out to the particular beneficial insect that is most likely to prey upon the pest eating them.