Did you know that two different species of ditch-daisies grow in this area? I had no idea. I happened to be looking at iNaturalist one day and saw that some ditch-daisies were labeled as Bidens aristosa (which I expected), and others were labeled as Bidens polylepis. Both are commonly known as ditch-daisies. The flowers look the same. The leaves look the same. They grow in the same environments. Some botanists even consider them to be the same species and group them all as Bidens aristosa (but not the experts in North Carolina).
How can you distinguish between these two plants? After some digging, I found some answers. The distinguishing feature is the green bracts behind the flowers. Bidens aristosa has small green bracts that are about the same length as the yellow inner bracts. There are 8-12 of these green bracts, and they are straight. In Bidens polylepis, the green bracts are longer than the yellow inner bracts. Bidens polylepis usually has 12-21 of these green bracts, and they can be curled or twisted.
So, I gave myself the task to examine the ditch-daisies in the area and see if both of them are on the trails. I started on the Shiloh Greenway and found Bidens polylepis. I covered a quick mile between the Hatcher Creek and Crabtree Creek Greenways. The plants that I could examine the back of all appeared to be Bidens polylepis, but I wasn’t sure about a couple of them. I had time for a very small portion of the Indian Creek Greenway and that’s where I found several plants that were more likely to be Bidens aristosa.
The ditch-daisies are past their peak bloom already. I’ll try to cover longer portions of the trails to determine the population of both species. I’m so glad I was able to find both types before the flowers faded for the season!
Stay curious!