There are none.
The bulbous root is the only commodity for which futures trading is
banned. Back in 1958, onion growers convinced themselves that futures
traders (and not the new farms sprouting up in Wisconsin) were
responsible for falling onion prices, so they lobbied an up-and-coming
Michigan Congressman named Gerald Ford to push through a law banning
all futures trading in onions. The law still stands.
even with no traders to blame, the volatility in onion prices makes the
swings in oil and corn look tame, reinforcing academics’ belief that
futures trading diminishes extreme price swings.
Amazing, onion farmers and Congress panic in 1958 with the Senate Committee arguing that
…speculative activity in the futures markets causes such severe and unwarranted fluctuations in the price of cash onions…[that a] complete prohibition of onion futures trading [is necessary] in order to assure the orderly flow of onions in interstate commerce…
and for going on fifty years onion futures are banned. Makes me want to cry.
Hat tip to Newmark’s Door