Trading starts on January 1. You have to be signed up and have at least 1 kind of seeds offered by midnight December 31 to participate. There are 44 participants now, with over 2000 different seed offerings. It is easy to join the swap, look around and see how the swap works and what is being offered, and easily "unjoin" if you find it is not for you. For more information and to join: https://garden.org/apps/swap/view/11/

If you are not already a member you do have to join garden.org to participate, but that is free.