We all know that plants respond to light, gravity and touch. But is there any merit in singing to them?

We put this question to the BBC Earth Facebook audience. Anecdotally, a few of you seemed to suggest that singing to plants was helpful.

"I had a yucca that I used to wash the leaves of once a week and sing to as I did it," says Heather Louise Goodall. "It grew from being about 2 feet tall to 7 feet tall in just a couple of years. In the end it got too big for the house."

"My best friend's dad is the best plant grower I know. He swears you should sing to them. He didn't explain why," says David Michael Goeke.

Several of you had some ideas of how singing could help.

"Singing, or even talking, produces carbon dioxide," says Chelsea Garcia Ortega, a point echoed by David Souther. "Plant[s] convert carbon dioxide into oxygen. Even if there is no benefit to the plant, there could be benefit to yourself by producing more [oxygen] inside."

Come on, says Marshal Huang. There has got to be more to it than carbon dioxide levels.

There is precious little scientific research into the subject

Perhaps there could be good vibrations, suggests Christie Ley. "Back in the early 70s a friend's son experimented with plants, playing classical and hard rock to plants," she remembers. "The ones he played classical to thrived. The hard rock ones died..."

Caroline Wall has a neat hypothesis. It need not be anything to do with sound at all.

Instead, maybe people who sing to their plants are just better at looking after them. "You're more likely to remember to water and care for the plant if you're taking the time to serenade it, even potentially noticing issues sooner than you might otherwise," she says.

As intriguing as all this is, we are getting ahead of the science. What does that tell us?

"This is quite a near-esoteric subject," says Wolfgang Stuppy, research leader of comparative seed biology at Kew Gardens in London, UK. "There is precious little scientific research into the subject and certainly no scientific proof that plants could benefit from anybody singing to them."

When Darwin played his bassoon to the plants, the results were inconclusive

But Stuppy does not rule it out. "This doesn't mean that it is impossible."

Charles Darwin was similarly open-minded. He once noted that seedlings appeared to be sensitive to the vibrations of the table on which their pots were standing.

Intrigued, he devised what he called "a fool's experiment" to see if the seedlings responded to sound. "I shan't be easy till I've tried it," he told his son Francis. But when Darwin's son Francis played his bassoon to the plants, the results were inconclusive.

More recently, evidence has emerged that some sounds may cause subtle changes in some plants at some stages of their life cycles.

Ultrasound, with frequencies higher than those in the audible spectrum, may enhance seed germination. Experiments on chrysanthemums suggest that audible sound can alter levels of growth hormones in cells.

What's more, the roots of maize seedlings appear to turn towards sounds at a certain frequency. Researchers in Korea have also found that some frequencies increase the expression of some genes.

Clever experiments with young chilli plants show that they can sense the presence and identity of neighbouring plants, through some unconventional and as-yet-unidentified mechanism. Vibrations might play a role.

"Some plants even produce oils to scare off insects when played the sounds of an insect chomping on some leaves," says Matthew Portelli. It might sound nuts, but he is right. In 2014, scientists reported that the mere sound of chewing caterpillars was enough to prime thale cress plants to release more defensive chemicals in a subsequent attack.

So the idea that plants might be able to respond to song is perhaps not as barmy as it sounds.

Whether it is good for growth is another question entirely. "Any plant would curl up and die if I sang to it," says Denise Howes.