This is an acorn that I've found in abundance is Rockford, Illinois, USA. I think it may be a red or black oak but I'm not sure. It has a very distinct look with the line showing separating the two halves.
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Sign up to join this communityThis is an acorn that I've found in abundance is Rockford, Illinois, USA. I think it may be a red or black oak but I'm not sure. It has a very distinct look with the line showing separating the two halves.
[![enter image description here][1]][1]
I'm pretty sure that the nut is one of the less-common hickories - probably bitternut (Carya cordiformis). The nut of this species is very smooth and does not have ridges like other hickories. It also has the same point at the bottom that's in your photo, and appears to have a central line. Here are some photos:
Pignut https://davesgarden.com/guides/pf/showimage/57394/
Bitternut http://www.friendsofeloisebutler.org/pages/plants/hickory_bitternut.html (go to the bottom of the page for the photo)
Lots of hickories https://iythealth.com/hickory-tree-nuts/ (great photo of a number of species at about the middle of the page)
The bitternut's range is correct for you - it's found throughout Illinois and into central Wisconsin.