So there's a thread here where you can post things you want to trade or are looking for:
Not sure if this is allowed but what the hell. I’ve not been reprimanded here yet, so let’s get this party started! Rules are simple. Post what you want and what you’ve got. It’s a seed for seed swap, no exceptions. Post the quantity you’ve got and update your post with the correct...
phenohunter.org
Otherwise a lot of trades just happen organically through casual conversations. Like Bodean said, if your engaged with people it will come about, and we just swap details through direct messages or emails.