This is called The Return of the Giant Hogweed

Turn and run!
Nothing can stop them
Around every river and canal their power is growing

Stamp them out!
We must destroy them
They infiltrate each city with their thick dark warning odour

They are invincible
They seem immune to all our herbicidal battering

Long ago in the Russian hills
A Victorian explorer found the regal Hogweed by a marsh
He captured it and brought it home

Botanical creature stirs, seeking revenge
Royal beast did not forget
He came home to London
And made a present of the Hogweed to the Royal Gardens at Kew

Waste no time!
They are approaching
Hurry now, we must protect ourselves and find some shelter
Strike by night!
They are defenceless
They all need the sun to photosensitize their venom
Still, they're invincible
Still, they're immune to all our herbicidal battering

Fashionable country gentlemen had some cultivated wild gardens
In which they innocently planted the Giant Hogweed throughout the land

Botanical creature stirs, seeking revenge
Royal beast did not forget
Soon they escaped, spreading their seed
Preparing for an onslaught, threatening the human race

Mighty Hogweed is avenged
Human bodies soon will know anger
Kill them with your Hogweed hairs
Heracleum Mantegazziani

Giant Hogweed lives!