The Roar singer joined the Prince of Wales and the Duchess of Cornwall at a black tie dinner at Banqueting House in London on Tuesday evening where she was named an ambassador of his British Asian Trust (BAT) as part of a major drive against child trafficking.
Perry, 35, announced the Prince on stage saying: "I'm excited to be here because I'm a big fan of his royal highness and all the work that he has done and is continuing to do, especially in India for children.
"In my own personal experience, he has an incredibly kind soul. So kind, that yes, sometimes he talks to his plants.
"And he asked me if I could sing to his plants. And I will, in the future, you have my word, sir."
The 71-year-old heir to the British throne is a devoted gardener who revealed in an interview in 1986: “I just come and talk to the plants, really – very important to talk to them. They respond.”
Prince Charles said he was "enormously grateful" for her "kind introduction".
He added: "She told me just now that she wanted to make it slightly more spicy, but I think she resisted the temptation.”
The prince went on: "But I must say it was a great pleasure to have met her in Mumbai last November at a gathering for British Asian Trust council members on the day before my birthday. Meeting her turned out to be a wonderful birthday present."