The Nikon 200 mm macro lenses has proven to be incredibly valuable to me over the years. Indeed, if I could only have one 35mm lens, it would be the Nikon 200 mm macro.
Longer lenses are great for wildflower portraits for two major reasons.
First, long lenses give you great working distance which is the distance between the front of the lens and the subject. Working distance is critical at times in doing wildflower portraits because it allows you to reach into a patch of flowers to isolate a single blossom while permitting you to stay out of the patch to avoid stepping on a hapless flower. Secondly, bad backgrounds in wildflower photos are problems for many photographers because they use short focal length lenses for their portraits. The easiest way to simply the background is to use a longer focal length lens because they have a smaller angle of view than short lenses like the 50 mm macro. In other words, lenses with narrow angles of view like the 200 mm lenses don't see as much of the background so they tend to be less distracting.