Many thanks for the comments.
New growth is remarkable in it's property of being both very reflective and producing a very bright almost luminous colour when backlit. In sunlight the reflection off each leaf is a pinpoint of near white surrounded by a subtle fringe of colour. Contrast and sharpening tools are not your friends here as both destroy the effect. Contrast just darkens the colour fringe and so removes part of the impression of light. Sharpening does the same on a local scale, and as the leaves overlap adjustment on one destroys the neighbours.
Instead I dropped the exposure and highlight values in raw and then lifted them again in PS. I used a curves adjustment layer with a distinct "shoulder" in the highlights. I have reduced the local contrast of the highlights by lifting the values close to the whites to try and maintain the impression of light.
I applied this effect locally to the centre of the image using an opaque mask around the rest of the forest and a pure black to the foreground as I didn't want the slight hike in the shadow/mid contrast. I wanted to maintain the softness here and it helps boost the center of the image by way of "relative" values.
It can be no secret that I feel Ansel Adams was a master at this, and so I have always paid great attention to anything he has said about his images. Unfortunately with my B&W if find that removing the subtle high green values I have also removed a lot of separation in the highlights. Still, it's good practice.