Black-eyed
Susan (Rudbeckia hirta)
Gardeners raise plants, botanists classify them. To most of us a
Black-eyed Susan is any yellow, daisy-like flower with a dark center but
to botanists that name applies only to Rudbeckia hirta, not
to R. fulgida which to our naked eye is pretty much identical.
Rudbeckias are in the Daisy or Composite family, so-called because their
flower is actually a composite of many tiny, tiny flowers. Some of
these are attached to the petals and are called ray flowers. The others
are in the center knob and are called disk flowers.
A key difference between R. hirta and R. fulgida is that in
the former the Y-shaped styles (a section of the female part) of the disk
flowers have slender, pointed prongs. Those of R. fulgida are short
and blunt.
You need a good hand lens or a microscope to see that difference but
aren't you glad you asked?. (A 10 power lens for is good for most
wildflower identification work.)
Provided by:
Glenn P., Arboretum
Volunteer
Photo by: Angela B., Arboretum Staff