You may have heard somewhere that talking to your plants can stimulate them to grow faster and healthier. Whether or not this has inspired you to perform enthusiastic monologues in your garden, it's worth finding out if the myth is actually true.
According to Penn State University, the theory that plants can actually benefit from humans talking to them was first published in a book from 1848, written by a German professor named Gustav Fechner. Since those early days, many more books have been written about the idea of plants responding to sound stimuli. In fact, in 1970 a dentist recorded an album specifically meant to be played for flowers and plants!
Despite the amount of speculation on the subject, there's still not much conclusive research on the topic of plants responding to human conversation. However, some scientists and researchers have found evidence that plants do react to a number of environmental stimuli, including vibrations. Since sound is essentially a form of vibration, it's entirely plausible that speech and sound could have an effect on plant growth.
Some scientists believe that plants evolved to respond to vibration in order to help them survive in windy environments. Plants that are repeatedly exposed to wind produce a hormone that keeps them short, with thick stems to help them stay rooted. Other researchers have proposed that it's the carbon dioxide produced by human speech that has an effect on plant growth, but that theory isn't well-established. People would have to be talking to their plants for several hours each day in order for the carbon dioxide to significantly affect the plants, and that would be pretty absurd.
The Discovery channel's popular show Mythbusters produced an episode in 2004 that explored the possibility that plants respond to speech. They set up multiple greenhouses, four of which were equipped with stereos playing looped recordings. Two were of negative speech, while two were of positive speech. The fifth greenhouse had classical music playing, while the sixth had heavy death metal. A seventh greenhouse, set up as the control specimen, had no music. The team found that the plants in the four greenhouses with recordings grew faster than the control plants, and that the plants in the greenhouses with music grew even faster. The plants exposed to heavy metal grew the best out of all.
Even if it's not entirely proven, it's totally possible that your potted plants, tulips and roses can respond to sound. Don't be afraid to buy plants online and start talking to them!