I found these place-cards online and yes, the creative wheels are turning again!
Images from Hotref
You can purchase place cards from sites such as Hotref or Asian Ideas, from prices ranging from $8.39 per pack (sets of 12) to $16 each set. They include instructions and the very cute phrase "Please be Seeded." There are also sites that offer invitations and other stationery you might need on this very cool paper.
You can DIY it. Check out sites that sell individual sheets of seed paper such as Botanical Paperworks or Plantable Papers.
And if you think you can rival Martha Stewart in the crafty department, you can even try making your own plantable paper. Wow, major DIY goddess!