Found this on World Travel Guide:

Prohibited Imports
Narcotics, firearms, ammunition, weapons, most meat and dairy products, eggs, plants, potatoes from outside the EU, endangered species, fireworks and alcoholic beverages of over 60% alcohol.

So, looks like you're in the clear, unless they consider seeds a "plant". :)

-John

I'll get some Drama Queen poppies in return!

I would call someone and try to find out more info. It is definitely illegal to send seeds to some countries. I don't know the details, but it would be better to check it out first than to have to learn about it after being questioned by the feds. Call the main branch of your local library and see if they have a reference department. If it's like our library, they should be able to give you a complete and very informative answer probably the same day you call.

See the link for what the USPS won't allow you to ship to Sweden. Just send the seeds. :) If Swedish customs (for whatever reason) decides they don't want your Datura seeds in their country, they just seize the package - the Feds don't come knocking at your door. :)

Here is a link that might be useful: USPS Guidelines - Sweden

Also, check and see if the seeds you are getting in return are allowed into the US. I would think so, but it doesn't hurt to know.

Heck, I've got opium poppies growing by the road.

I've spent a few hours looking at the export regulations and the only thing that I can find that could get you in trouble is if you sent seeds that are banned for reasons like if they are considered an endangered species or a noxious weed by the US govt. There are also regulations about patented varieties but that wouldn't apply here. So it does sound like it would be OK for you to ship them. The stories I have heard about the feds coming to visit involved endangered species and, from what I have read, they can get pretty nasty on this. It looks like there is more potential for legal trouble when you send seeds to some other states than there is if you send them overseas.

I didn't see anything about why to do this, but some articles I have read recommend labeling the package with something like "flower seeds / no cash value".

E-mail the Swedish Embassy. They can probably tell you.
http://www.swedenabroad.se/Start____6989.aspx
Sometimes countries require fumigation of agricultural products to prevent the spread of invasive germs and insects.
I think you'll have more trouble getting something into the US than getting it out.