-Create evil twins for morgia and moss : sure, using certain drugs helps you, but others have bad effect on your sanity/health/self control.
-Create more herbs. In particular, this could go VERY WELL with a cook race. I remember the parsley.
-Rotting corpses make compost. Yes, this could be used alot. but good farmers also have sheeps
- Some monsters who could eat herbs. This would help in scumming regulation as well as being a proficient farmer = it's still the way your herb are placed more than their number which will determine what a good field could be.

-Introduce workable fields. The gardnener could buy some herb seed (alot), make a field, and make it loan. Depending on the loaner, the state of the field when the loaner comes by would be the same, or not :)
- Introduce fruit trees. Just imagine (again) the possibilities. God, you could make a happy life and all, selling fruits. Which can also grow explosive grenades or things of the kinds. Explosive bombs grow on tree. Basicly, a tree would need water too, much more than herb, planting it just right to the river could be a bad idea, too far too.