My first Hops spawned from Stickreeds. They grow slow like wheat though, and look exactly like wheat until about half-way from being full grown since it starts turning more dark green.
On my search for coffee, it turns out a combination of Netherwart and Cocoa can give Ferru for some reason. It also gave me melons one time and dandelions another time though.
I'm playing in SMP, and have gotten all variety of crops other than Coffee. I need a list of what combinations you have tried that have given coffee crops. I still have info about the other crops I have bred, so I'm willing to share pointers of what I know in exchange for some coffee info.
Perhaps it has some odd requirement?
If I wanted to get coffee crops, but had no coffee crop seeds available, what would be a good example of plants to crossbreed in order to obtain coffee crops?
Based on my own crop experiments in SMP, I've gotten my first Ferru, and Aurelia seeds from crossbreeding a pair of Redwheat plants. I'd suggest you try to get redwheat first (since they have a weird light requirement compared to other crops), then go cross them into themselves. In my experience they also seem to go crossbreed themselves into a variety of lower tier plants like melons.
If you're wondering how I got to redwheat:
Stickreed Pair -> Hops
Hops + Stickreed or Hops Pair -> Redwheat (this needs a controlled light environment though)
May I ask how you gotten coffee though? It's the only plant I have yet to breed successfully.
As far as I know, there really are some plants that only emerge from certain cross combos...