The land adjacent to the runways at my gliding club in Western Canada is leased to a farmer. Every third year, he plants rape, or Canola as it is more politely known in Canada.
Very colourful when flowering, but our pilots are particularly careful not to run off the runway on those years, because the crop is like a forest of one metre tall trees, with very robust stems about 1 to 2 cm in diameter. Extremely unforgiving.