pe.usps.com/text/imm/ab_toc.htm In the US you can go here and see if you can ship seeds, plants, etc. Note, that in the receiving country, anything goes. Even if it's not on the list of prohibited or restricted.
The International person wrote to me to say that the when he filled out the customs document in his country to send seeds to the U.S. or Australia...the post office refused to take the shipment.
The above list always has something interesting. For example, when you click on the link for Italy, you cannot send any of the following items:
Albums of any kind (of photographs, postcards, postage stamps, etc.).
Arms and weapons.
Articles of platinum or gold; jewelry; and other valuable articles unless sent as insured Priority Mail International parcels.
Artificial flowers and fruits and accessories for them.
Bells and other musical instruments and parts thereof.
Cartridge caps; cartridges.
Clocks and supplies for clocks.
Compound medicaments and medicines.
Coral mounted in any way.
Ether and chloroform.
Exposed photographic and cinematographic films.
Footwear of any kind.
Haberdashery and sewn articles of any kind, including trimmings and lace; handkerchiefs; scarves; shawls, needlework including stockings and gloves; bonnets, caps, and hats of any kind.
Hair and articles made of hair.
Human remains.
Leather goods.
Lighters and their parts, including lighter flints.
Lithium cells and batteries — including items containing lithium cells and batteries under 135.6.
Live bees, leeches, and silkworms.
Live plants and animals.
Nutmeg, vanilla; sea salt, rock salt; saffron.
Parasites and predators of harmful insects.
Perfumery goods of all kinds (except soap).
Playing cards of any kind.
Postage stamps in sealed or unsealed First-Class Mail International or First-Class Package International Service shipments.
Radioactive materials.
Ribbons for typewriters.
Roasted or ground coffee and its substitutes; roasted chicory.
Saccharine and all products containing saccharine.
Salted, smoked or otherwise prepared meats; fats; and lard.
Tobacco.
Toys not made wholly of wood.
Treated skins and furs.
Weapons of any kind and spare parts for them.
Now, some of these things make perfect sense...some for safety, some to protect their own industries...but when I want to send my friends photos of their visit here, I have to lump them in a box, I can't put them in an album...
Now, nowhere on this list does it say seeds. Yet, time and time again on the Italian side of the pond, whoever is holding the package decides if it can be delivered or not.
And the latest in sending something to NZ? The post office clerk asked me if I wanted the package returned to me if it was unacceptable to NZ Customs, at my expense or destroyed there?