Since January, 2002, the Animal and Plant Health Inspection Service, Plant Protection and Quarantine (APHIS-PPQ), of the USDA, has required a phytosanitary certificate for all imported seed, including the small packets of seed from foreign seed exchanges and private seed houses. Four years of effort produced a new Permit, for Small Lots of Seed, that allows the importation of these small packets of seeds without a phyto.
U.S. importers who plan to purchase seed from any groups or individuals based outside the United States should obtain this new permit. It is free, good for three years and multiple uses, and the application is available online. Best of all, it does not require that the exporter provide an expensive, time-consuming phyto.
For information about getting the permit:
https://www.nargs.org/small-lots-seed
This program does not always work well. I tried mailing seeds to a Washington state inspection station, following all regulations, and the inspector somehow lost the enclosed mailing label required to mail the seeds on to the person who had requested them. I finally succeeded by NOT following instructions. I printed the recipient's address on the envelope, under the big label with the inspection station's address, so that when the inspector ripped that label off, there was the next address.
When this procedure first went into effect, seeds sent to the inspection station in Jamaica, New York, sometimes got sent to Jamaica.