I remember back in the early 1970s when a book came out called The Secret Life of Plants (P. Tompkins, C. Bird). The book discussed alternative views of plant life, including suggestions that plants were sentient beings, and that by talking to them, we could not only become more relaxed horticulturalists, but the plants would be happier, too. It inspired my mother to have the occasional chat with the African violets on the kitchen windowsill for an entire summer. I can’t speak for the violets, but my mother definitely got bored, and the violets didn’t seem any better or worse for all the encouraging words.

Overall, the notion that plants were sentient, conversation-capable creatures was chalked up to the post-1960s lovey-dovey wish for interconnectedness rather than given credence as having any firm basis in scientific methodology.

But thirty years of research, changed perspectives and better equipment have been showing that plants can, indeed, communicate in a variety of ways, both with other plants and with animals, mostly insects.

There’s this, about plants talking between species:

A new study released this month shows that when plants are connected via an underground network of the common mycorrhizae fungi, the fungi act as “a conduit for signalling between plants, acting as an early warning system for herbivore attack.” The signals not only warn of an attack, they also work to attract enemies (in this case, a specific kind of wasp) of the attacking pests (aphids). Mycorrhizae fungi inhabit the roots of many plants, providing nutrients in exchange for carbon, but this communication takes the relationship a step further. Once alerted by plants under attack, uninfested plants that were connected to the network could start mounting their defences.

A 2001 study published in Science talked showed tobacco plants (Nicotiana attenuata) fighting herbivore attacks by releasing volatiles to attract predators, which would then come and feed on the eggs of attacking pests. The plants were able to reduce pest populations by up to 90%.

Fine, but this is still in the realm of chemical communication. It’s unseen, and it’s not like the plants are actually talking to each other in the sense that we understand vocal communication.

And then there’s this:

A study in BMC Ecology provides evidence that chili seeds, known to grow more vigorously when in the presence of basil plants, do so even if cut off from any chemical or light-related signals with those ‘beneficial’ plants, indicating some form of ‘alternative signaling channel’. Monica Gagliano, a plant acoustics researcher, suggests that vibrations are the signaling mechanism, which would imply that plants can hear. Or at least, they are responsive to minute sound vibrations.

And finally, there are the people who listen to trees:

From LiveScience: “Air bubbles form when a tree is trying to suck moisture out of dry ground during droughts. As leaves on a tree collect carbon dioxide, they open their pores, a process that leaves them vulnerable to water loss. Lab experiments at Grenoble University in France have isolated ultrasonic pops, which are 100 times faster than what a human can hear, in slivers of dead pine wood bathed in a hydrogel to simulate the conditions of a living tree. The race is now on between researchers to create equipment capable of listening to tree sounds.”

Why? So we can better identify trees that are in distress. Earlier studies have shown that bark beetles may be able to hear which trees are more vulnerable to attack during drought conditions due to the air bubbles that form. Humans might be able to listen to the trees to assist them.

Did I mention that mycorrhizae fungi networks are vast and complex in many natural habitats? Who knows just how complicated these conversations might be?

My mother would have been so thrilled to know her conversation wasn’t entirely one-sided. She just needed to know how to understand the signals.

More:

Ecology Letters study – Underground signals carried through common mycelial networks warn neighbouring plants of aphid attack by Z. Babikova, L. Gilbert, T. Bruce, M. Birkett, J.C. Caulfied, C. Woodcock, J.A. Pickett, D. Johnson

BBC News article – Fungus network ‘plays role in plant communication’

Science AAAS study (2001) – Defensive Function of Herbivore-Induced Plant Volatile Emissions in Nature by A. Kessler & I.T. Baldwin

Discover Magazine article (2002) – Talking Plants by S. Russell & M. Aguilera-Hellweg

BMC Ecology study – Love thy neighbour: facilitation through an alternative signalling modality in plants by M. Gagliano & M. Renton

LiveScience article – Sound Garden – Can plants actually talk and hear? by Becky Oskin

LiveScience article – Thirsty Wood’s Distress Call Heard in Lab by Elizabeth Howell