I'm feeling a bit better about this one today.
I've discovered that Prussian Blue and Brown Madder make a nice black that can easily go either warm or cool by altering the proportions just a little. Add a little lemony yellow (in this case Winsor Yellow) and it becomes a very dark green.
I started this painting because of a challenge in an online watercolor group -- to do a green painting without using green paint. But this is turning out overwhelming green. I need to pull in more warmth. Maybe I'll let the darks go more brownish red than I've done so far and see how that works.
My other concern is that, when I did the initial underpainting, I lost all of the whites. Truthfully, there are no whites in my reference photo, but I may have to do some scrubbing or use some opaque white at the end, just to relieve my eye from all this yellow and green.