There's a patch of ground roughly twenty meters wide near the town of Harpenden, half an hour's train ride north of London. Many such patches are found nearby, but this lawn, a short walk from the red-bricked gables of Rothamsted Manor, is a sliver of English meadow as it may have been more than 250 years ago. It's also Plot 3 of the famous Park Grass experiment that John Bennet Lawes founded in 1856 and is still going strong.












