Each grain option is American type, therefore the option may exercise any time prior the expiration. The maturity structure coincides with the structure of underlying futures contract, namely the given maturities and the belonging options series open in advance 17 months.
Grain Options
Grain options are based on the most liquid futures contracts (wheat, sunflower-seed, corn). The underlying of grain options are the futures contracts with the same maturity, thus the exercise opens a futures position of the given product.