Done! I decided the red of the berries was enough to break up all the green. I was afraid adding burnt sienna would 'muddy up the waters'.
This is fairly small...10" x 7". To complete the berries I did an underpainting using indigo mixed with a little crimson lake to indicate the shadows and create volume, then finished with a few washes of crimson lake to get that strawberry red color. There's probably more I could do to this but it's time to set it aside. I'll get it back out in a few weeks or months and if I still like the way it looks it'll be 'officially done'.