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 odor
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
The royal beast did not forget
So he came home to London
And made a present of the Hogweed to the Royal Gardens at Kew

Waste no time
They're approaching
Hurry now, we must protect ourselves and find some shelter
Strike by night
They're defenseless
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
The 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