John Keats could not see the flowers that surrounded him as he listened ‘darkling’ to his Hampstead nightingale, although from their scent he guessed them to be hawthorn, sweetbriar, sweet violets and ‘the coming musk rose’. A few miles away, in Epping Forest, but two decades later in time, John Clare was to listen to another nightingale singing, as the species mostly does, by daylight – the light of a long May evening in which the poet's eye would distinguish, below the intense green of young beech and hawthorn leaves, a ground layer of bracken, orchids and foxgloves, ‘where mugwort grows like mignonette’. Mugwort was familiar to Keats from his medical studies. But it is difficult to imagine him giving it a place in his verse; whereas the flicker of self-mockery in ‘like mignonette’ suggests that Clare knows Artemesia vulgaris to be as much at home in his poetry under its common name as sweetbriar is in Keats's ode under its pastoral name of eglantine. As honest, sturdy mugwort, it takes its due place, alongside ragwort, fleabane and sow thistle, among the 370 plants that Clare actually names in his poetry and prose.

This is an astonishing tally. Indeed the list is so comprehensive that when Clare fails to mention a common wild flower we find ourselves asking why.