How Plants Communicate: Chemical Signals, Roots and the “Wood Wide Web”

Plants communicate mainly through chemistry: they release airborne volatile compounds that warn neighbouring plants of insect attack, exude chemicals from their roots, send electrical signals internally, and may exchange resources through underground fungal networks. Some popular claims about the “wood wide web” have been overstated, but the core finding – that plants detect and respond to each other – is well established.

Do plants really communicate?

In biology, communication means one organism releasing a signal that another detects and responds to. By that definition, plants communicate constantly – with each other, with insects, with fungi and with microbes. They do it without eyes, ears or a brain, using an extraordinary chemical vocabulary.

1. Airborne chemical warnings

The smell of freshly cut grass is a distress signal. When leaves are damaged, plants release green leaf volatiles and other compounds within seconds.

• In the 1980s, researchers found that willow and poplar trees near insect-damaged trees increased their own defensive chemicals. The findings were controversial at first but have since been confirmed in many species.
• Sagebrush in the US west releases methyl jasmonate when clipped; nearby wild tobacco plants exposed to it suffered less insect damage in field studies.
• Lima beans exposed to volatiles from damaged neighbours produce more extrafloral nectar, which attracts protective ants.

2. Calling in bodyguards

Some plants recruit the enemies of their enemies:

• When caterpillars chew corn (maize) leaves, the plant releases a blend of volatiles that attracts parasitic wasps, which lay eggs inside the caterpillars.
• Corn roots attacked by rootworm larvae release a compound called (E)-β-caryophyllene that attracts nematodes which kill the larvae. Many modern US maize varieties have lost this ability through breeding.

3. Root signals and kin recognition

Below ground, roots release a cocktail of sugars, amino acids and secondary compounds called root exudates. These shape the soil microbes around them and can affect neighbouring plants.

• Allelopathy: black walnut releases juglone, which inhibits the growth of tomatoes, apples and many other plants near it.
• Kin recognition: experiments with sea rocket (Cakile edentula) found plants grew fewer competitive roots when sharing pots with siblings than with strangers.

4. The “wood wide web”

Most land plants form partnerships with mycorrhizal fungi, which wrap around or penetrate roots, trading soil nutrients and water for plant sugars. Fungal threads can link several plants at once, forming common mycorrhizal networks.

Research in the 1990s by Suzanne Simard and colleagues suggested carbon could move between birch and Douglas fir trees through these networks, inspiring the “mother tree” idea and the term “wood wide web”.

5. Internal electrical signals

Plants have no nerves, but they do transmit electrical signals. When a caterpillar chews a leaf of Arabidopsis, a wave of calcium ions, visualised with fluorescent proteins in a famous 2018 study, spreads to distant leaves within minutes, triggering defences. The Venus flytrap uses similar electrical impulses to snap shut – see how carnivorous plants work.

6. Talking to pollinators

Flowers advertise with colour, ultraviolet patterns invisible to us, scent, and even electric fields. Bumblebees can detect the weak electrical charge of flowers and learn that recently visited flowers carry a changed charge. Find out more in why do plants smell?.

Can plants hear?

Some intriguing studies suggest plants respond to sound vibrations: evening primrose flowers produced sweeter nectar within minutes of being exposed to the sound of a flying bee, and Arabidopsis ramped up defences when played recordings of caterpillar chewing. A 2023 study reported that stressed tomato and tobacco plants emit ultrasonic clicks. These findings are exciting but early.

Why this matters

Understanding plant signals could lead to crops that defend themselves with fewer pesticides, companion planting that works by design (see companion planting with herbs), and a deeper appreciation of the hidden life of gardens and forests.

Frequently asked questions

Can plants talk to each other?

Plants do not talk, but they exchange chemical signals. Damaged plants release airborne compounds that can trigger defensive responses in neighbouring plants.

What is the wood wide web?

The wood wide web is a popular term for underground networks of mycorrhizal fungi that connect the roots of different plants. Scientists still debate how much information and resources pass between trees through them.

Do plants feel pain?

Plants detect damage and respond with chemical and electrical signals, but they lack a nervous system and brain, so most scientists believe they do not experience pain as animals do.

Can plants hear sounds?

Some studies suggest plants respond to vibrations, such as the sound of buzzing bees or chewing caterpillars, but this field of research is still young.

Why does cut grass smell?

The smell of cut grass comes from green leaf volatiles that plants release when damaged. They act as a warning signal and help attract predators of herbivores.

Sources and further reading

• Karban R (2015) Plant Sensing and Communication. University of Chicago Press.
• Toyota M et al. (2018) Glutamate triggers long-distance, calcium-based plant defense signaling. Science.
• Karst J et al. (2023) Positive citation bias and overinterpreted results lead to misinformation on common mycorrhizal networks in forests. Nature Ecology & Evolution.
• Khait I et al. (2023) Sounds emitted by plants under stress are airborne and informative. Cell.