In our area there are four species of Rudbeckia that might be present in a remnant or restoration. Also, Ratibida pinnata is generally present
and may sometimes confuse things. These species are commonly called coneflowers
or black-eyed Susans. In the field it may be difficult to decide which is which. Because
most of these species are planted in native plant gardens, there are numerous
cultivars, often with additional names (for instance Rudbeckia hirta ‘Autumn Colors’ ‘Indian Summer’). Many of the
commercial plant and seed companies don’t provide enough detail to permit easy
identification.
Ratibida (yellow
or gray headed coneflower) is the most straightforward to distinguish. Its ray
flowers always hang down and its disk flowers are tall and compact, providing a
characteristic flower structure.
Rudbeckia laciniata
(cut-leaf coneflower) can be distinguished from the other Rudbeckia species because its disk flowers are yellowish or grayish-green rather than purple. Also, it lives in moist places and shores and its lower
leaves are pinnately divided. Although laciniata is listed in Czarapata’s book as a
potentially invasive species in the upper Midwest, we have never seen any
evidence of it getting “out of hand” at Pleasant Valley Conservancy. It was
already present in our wetland when we first started restoration, and
has never “taken over”. It is a tall plant and provides a nice backdrop in the wet prairies.
Rudbeckia triloba (brown-eyed
Susan) is easily distinguished because its lower leaves are tri-lobed. Also,
its flowers are smaller, with the ray and disk flowers both shorter than the
other species.
Rudbeckia triloba
is a short-lived perennial which establishes well and readily self-seeds. Once
planted in a prairie it should continue as a colorful species for many years,
even though it may move around. Some Wisconsin “purists” question whether it is
“native” to our region, since it can often be found in disturbed habitats.
However, our experience at Pleasant Valley Conservancy is that it is well
behaved, and provides an attractive color late in August when many other
species are starting to fade. It also does well in the more sunnier areas of
the savannas.
Finally, we need to separate hirta from subtomentosa. hirta
has a simple narrow leaf, whereas subtomentosa
has a dissected leaf, as shown in the photos. As always with leaf shape, the
lower leaves tend to be more reliable than the upper ones. Even then, leaf
shape can often vary, so that this character is not always reliable. The best
character, from my observations, is the stem. hirta’s
is stiff and hairy, whereas subtomentosa’s
is smooth and glabrous. Run your hands up the stem and feel the difference.
Rudbeckia hirta
(black-eyed Susan) is an annual, biennual, or short-lived perennial. Some
botanists consider it an “aggressive weed”, but you will find it in almost
every planted prairie in southern Wisconsin. It is very reliable in a prairie
planting, easy to establish and provides guaranteed color by the second growing season. A single patch may not persist but it seeds well and should remain as a long-lived member
of the prairie.
R. subtomentosa (sweet
black-eyed Susan) is a long-lived perennial. At Pleasant Valley Conservancy we
never knew we had this species until it was recently pointed out to us by a
visitor. Sure enough, we found quite a bit of it in the Barn Prairie as well as
in the wet prairie nearby. Where did it come from? Seed heads of these two
species will be quite similar, and it seems likely that seeds of both species
could easily end up in a single mix. So we undoubtedly planted it accidentally. According to
the Herbarium records, it is found mainly in southwestern Wisconsin, along the
lower Wisconsin and Sugar rivers. However, with so much prairie planting going
on these days in Wisconsin, I suspect those restrictions will no longer apply.
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| Rudbeckia hirta (black-eyed-Susan) |
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| Hairy stem of black-eyed Susan |
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| Leaves of black-eyed-Susan |
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| Smooth glabrous stem of sweet black-eyed Susan |
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| Tripartite leaf of sweet black-eyed Susan |
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| Rudbeckia subtomentosa (sweet black-eyed Susan |
