Seeds Are Regulated Cargo — and Bone Dry Is the Rule
Seeds look like the most trivial thing you could put in an envelope, and they are among the most regulated. The reason is biological, not bureaucratic: a seed is a dormant organism engineered to survive travel and then colonize wherever it lands. That is precisely what invasive-species and plant-disease law exists to prevent, which is why the USDA's Animal and Plant Health Inspection Service (APHIS) and state agriculture departments take an interest in a packet that weighs less than a letter.
The handling rule inverts everything our live plants guide teaches. A live plant needs its roots damp — moisture is survival. A seed needs to be bone dry, because moisture is what breaks dormancy: a seed that absorbs humidity in transit can begin to germinate inside its packet, or simply mold, and either outcome kills its viability. So the packing method is the opposite: paper packets or dry envelopes, no damp towel, no sealed plastic trapping humidity against the seed, and a moisture barrier around the OUTSIDE of the package if the route is wet. Dry, cool, and dark is the entire physical brief.
💡 The seed-vs-plant packing rule in one line: plants ship damp, seeds ship dry. If you're shipping both in one order, keep them in separate sealed compartments — the moisture that keeps a rooted cutting alive is exactly what ruins the seed packet next to it.
Domestic Shipping: The Noxious Weed List and State Lines
Most ordinary garden seed moves domestically without permits, which is why the home seed trade functions at all. Two exceptions carry real teeth. The first is the federal noxious weed list: species designated as noxious weeds are prohibited from interstate movement outright, and there is no permit that makes a casual shipment of them legal. The second is state-level import restriction — states run their own agricultural quarantines and prohibited-species lists to protect local agriculture, and a species that ships freely between two states may be barred from a third.
The practical workflow is destination-first: before shipping an unusual species, check the DESTINATION state's department of agriculture rules, not your own. States with major agricultural industries and fragile ecosystems tend to run the strictest regimes — the same jurisdictions our live plants guide flags for quarantine, for the same underlying reason. Label packages honestly with contents; a mislabeled seed shipment intercepted at an agricultural checkpoint turns a compliance question into an enforcement one.
International Seeds: Phytosanitary Certificates and Real Prohibitions
Crossing a border with seed is a different order of difficulty. Most countries require a phytosanitary certificate — an official document, issued by the exporting country's agriculture authority (in the US, obtained through your state's department of agriculture, typically for a modest fee), certifying the material was inspected and found free of pests and disease. Many destinations additionally require their own import permit, obtained by the RECIPIENT before the shipment leaves, and some species are prohibited outright or restricted under CITES.
Because that stack of paperwork is genuinely burdensome for a packet of seeds, the honest guidance for hobbyists is simply: don't. Casual international seed mailing — the friendly swap with an overseas gardener — is where well-meaning people accidentally break plant-quarantine law, and undeclared seed shipments get intercepted and destroyed routinely. If you must ship internationally, do it properly with the certificate and the recipient's import permit in hand, or buy from a seller already licensed to export into that country. And a related warning worth knowing from the receiving side: unsolicited packets of seeds arriving from abroad should never be planted — report them to your agriculture authority, because unidentified foreign seed is precisely the invasive-species vector this entire legal apparatus exists to stop.
The Seed-Saver Trade: Packets, Labels, and Viability
The seed-swapping and heirloom community moves an enormous volume of tiny shipments, and its conventions are worth adopting whether you're trading or selling. Package into paper seed packets or small paper envelopes — paper because it breathes, which prevents the trapped condensation that a plastic bag can create. Then place those packets inside a rigid or padded outer mailer, because the real physical risk to a seed packet is being crushed and shredded by postal machinery, not being dropped.
Labeling is the seed trade's discipline: species and variety, harvest year, and any relevant provenance. Harvest year matters because viability declines with age at rates that vary enormously by species — some seed remains reliably viable for many years in cool dry storage; others fall off sharply after a season or two. An unlabeled packet is a mystery of unknown age, which is worth little to a serious grower. Store and ship cool, dry, and dark; keep the outer package weatherproof; and label honestly. It costs nothing and it's the entire difference between a seed that grows and a packet that disappoints.