This was a bit of a scary stage. But then I thought it's only paper! I wet the entire background, and very carefully stroked in two different mixtures - a dark blue/gray and a dark blue/green. I don't usually do this sort of w/w application, and was worried the colors would explode all over the page. I think it has given a good impression of the out-of-focus branches.
This is where I am now. I thought about darkening some of the background branches, but I believe it would ruin the overall delicacy of the painting. So I have darkened the main branch and some of the petal centers in the focal area, and it is done!