Of all the statements for which the Prince of Wales has been lampooned, one has endured more than most in the public imagination and done much to cement his reputation for eccentricity. Now, more than two decades after he said that it was “very important” to talk to plants and that “they respond”, the Royal Horticultural Society is trying to determine if he was right.

It is conducting a study into how – if at all – the human voice affects tomato plants. Open auditions are to be held tomorrow at the RHS garden, at Wisley, Surrey, to find voices to make recordings of Shakespeare’s verse and John Wyndham’s The Day of the Triffids. These will then be played to ten plants around the clock.

Each tomato plant will “listen” to a different recording through the headphones of an MP3 player attached to its pot at root level. The plants will be kept in the same greenhouse and measured before, during and after the experiment. Control plants will be left in peace.

“One of the primary functions of the RHS is scientific research into plants and how to get them to grow better,” James Rudoni, the head of Wisley, said. “Prince Charles talks to plants. Let’s see if there’s something in this.”

Previous research has focused on the relationship between plants and music. An experiment involving rice plants found that classical music triggered activity in two genes. “The spoken word is slightly different and something we can explore a little bit more,” Mr Rudoni said.

Colin Crosbie, a gardens superintendent at Wisley who came up with the idea for the research project, is already convinced that plants respond favourably to human voices. “I’m a great believer. I definitely talk to plants,” he said. “Most gardeners are quite tactile and we do talk to them. Sometimes we talk kindly and sometimes we threaten them.

“Sometimes it’s gentle encouragement, but there are times with a plant when you say, ‘If you don’t do something this is the end. You are not producing flowers, I’m very sorry, it’s going to be the compost heap.’ It’s amazing how they respond,” he said. “People say I’m slightly mad, but I do believe in it, I really do.”

The voice recordings will be channelled to the roots, rather than leaves, because the gardeners believe that the sound will be better contained there and neighbouring tomato plants will not be confused by background noise from recordings other than the one intended for them.

It is hoped that the experiment might indicate the type of voice to which plants respond best. Trevor Cox, a professor of acoustics at the University of Salford, said: “It appears that low-frequency sound might vibrate the plant and so affect its growth. So my recommendation would be to impersonate Barry White, or some Buddhist chanting at a low frequency, to maximise the chances of success.”

A classified advertisement is to appear in The Times asking for volunteers to audition for the roles of readers to tomato plants. One spot has already been taken. The Times was recruited to make the first recording after taking part yesterday in the selection of the passages to be read.

This process was not undertaken lightly. Although the experts believe that the voices are likely to be more important than what is read, this science is in its infancy. It was felt that every effort should be made not to upset the tomato plants by inflicting on them Jeffrey Archer or Dan Brown.

The Day of the Triffids may read to human beings like a frightening vision of man-eating monster plants, but to a tomato plant the description of the arrival of the triffids in neglected gardens around the world may be nothing short of inspirational.

We toyed with The Black Tulip by Alexandre Dumas, but decided that we had to have some poetry. Although Wisley is blanketed in daffodils at the moment, Shakespeare had the edge on Wordsworth: whole books have been written about the flower and plants in the bard’s imagery. We plumped for Oberon’s speech in A Midsummer Night’s Dream that begins: “I know a bank whereon the wild thyme blows, Where ox-lips and the nodding violet grows.”

At the RHS they were at pains to point out that although the auditions are planned for April 1, this is not a joke. “It’s a bit of fun, but there’s science behind it,” Mr Crosbie said.

The truth about whether or not the Prince of Wales has been wasting his breath all these years may be of particular interest to the RHS patron. She is also his mother.

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