So in the film Denethor should not have been eating tomatoes as Faramir and co. went to their doom.
The field of corn (maize) in “The Fellowship of the Ring” probably shouldn’t be there, either. (It seems those wacky Brits have a habit of calling wheat “corn”, leading to much confusion.) But since the Third Age doesn’t correspond to any known period of European history in terms of biology, not to mention anthropology or geography, it doesn’t make that much difference what they grow in their fields.