At one point the Norfolk Groat (NG) fell to just 0.17 against Sterling, its lowest level since the Norfolk dumpling famine of 1840.
The currency crash has wiped millions off the value of farms across the county, Colman’s Mustard and Norwich City Football Club.
News first leaked overnight about how poor weather conditions would affect this year’s turnip crop.
The price went into a downward spiral and eventually settled at 0.24 against GBP when the Singapore exchange closed.
That means any Norfolk bumpkin wishing to visit Suffolk will have to find twice as many Groats to exchange for a British pound while on their international trip.
Currency trader Jeremy Swailes said: “Nothing spooks the markets more than downbeat forecasts about turnips. There was a huge run on the Norfolk Groat overnight, and the only people smiling were those who managed to short the currency before it collapsed.”
Norfolk turnip farmer Bubba Spuckler, who lives with his sister and their eight children, said: “What we need is a strong and stable Groat. Not a coalition of currency chaos.”
The groat remains integral to the Norfolk economy but was discontinued as legal tender in the rest of Britain from around 1860.
Traders are now waiting nervously for European foreign exchanges to open for business on Sunday night – and fear a further sell-off.