Apparently during the Depression, the court ruled that Congress could pass laws regulating wheat grown on farms, for a farmer's own use. It was argued that even when wheat was grown for personnal use,it could affect the price on the interstate market and therefore the Commerce Clause applied.
Ah yes, WICKARD v. FILBURN rears its ugly head.
It was not the fact that the farmer grew what - rather that he grew wheat in excess of his quota that he had agreed to. If he had not taken subsidies and agreed to the quota they would have had no action against him. While an oject lesson about "taking the King's shilling" it is in no way applicable to the subject at hand.