The Duke of Edinburgh wrote a letter to TV gardener Alan Titchmarsh to detail the work he had done in the parks of royal residences.
The broadcaster read excerpts from the note as he appeared in the BBC’s coverage of Philip’s funeral in Windsor.
Titchmarsh said the duke had a keen interest in gardening and added he would remember “being kept on my toes when I was with him”.
He continued: “Did he ever do anything half heartedly? He did everything with an eye to detail and he made sure it was right.”
Titchmarsh added: “I wrote a book on royal gardeners and sent it to the Queen, and had a letter back from the duke about a fortnight later.”
His book Royal Gardeners: The History of Britain’s Royal Gardens was originally published in 2003.
He said the duke told him he enjoyed the book and then “listed everything he had done in the home park including the avenues he had planted”.
He said the duke wrote: “I thought it might interest you to know active gardening still goes on.”
Titchmarsh told BBC anchor Huw Edwards: “I cherish the document.”