Thanks for your note. 

For earthy greens, my advice is to look to the mineral pigments.  Look at combining Yellow Ochre with Ultramarine Blue or Cobalt Blue.  Maybe try Titanate Green with a tiny bit of Cobalt Blue. One of my favorite deep greens is made with Hansa Yellow Medium and Carbon Black (just a smidge).  The key to mixing really good color is to mix in tiny, tiny increments.  Shift the Yellow Ochre ever so slightly with a teeny weensy bit of Ultramarine.  Don't just plop the colors together.  If you make these tiny adjustments and move the colors "incrementaly" it will give you much more control.