Skimming through the latest issue of The Garden, the RHS magazine, I spotted a short news story suggesting that plants appear to respond to the sound of chewing caterpillars by producing chemicals that are unpleasant to the pests. In the same study, it was found that other sounds do not induce the same response, including ones that are similar in magnitude and frequency. The conclusion is that there is some sense in which the plants hear signals of danger.

For further reading, Missouri University has both a lay summary page and a link to the full article describing the work.

Maybe talking to plants does make a difference to how they grow, although it could just be sending them into a panic and inadvertantly protecting them from herbivorous fauna!