Perhaps you are thinking of Johnny Appleseed, the American fantasy figure who planted all the apple trees in America. No more real than Rumplestiltskin or Jack Frost.
I don't think the website reference is as clear as it could be. "The Man Who Planted Trees" was written in 1954 by Jean Giono. The blurb on the cover of the edition published in 1989 reads; "In his wonderful story of Elzeard Bouffier, an imaginary yet wholy believable sheperd, Jean Giono perhaps hoped to inspire a reafforestation programme that would renew the whole earth." That seems pretty clear - false story, but a onderful little book with great woodcuts.