Armoracia rusticana or Horseradish is a vigorous, taproot forming perennial with rough, dark green leaves and panicles of white flowers - which are usually removed to encourage root development - but some grow the plant for its flowers.
Most however grow it for its splendid roots which make the hugely tasty and hot, horseradish sauce.
It is also a major element in the herbalist armoury being particularly efficacious in cleansing the bowels and/or sinuses, it is a good diuretic, a fungicide and is chock full of vitamin C.