The NOP Rule requires that organically produced and handled seeds be planted when such seed is commercially available for the variety. Annual transplants must always be organically grown unless the Secretary of Agriculture in response to a natural disaster or other major interruption issues a temporary variance. All seed used in organic production must be untreated, or treated only with substances (such as microbial products) that are on the National List. Farmers are required to use certified organic seed when it is commercially available. Commercial availability is based on ability to obtain the seed in an appropriate form, quality, or quantity, as reviewed by the certification agent.