Adding a bit more to this thread. It turns out we probably have an Ohio buckeye in the
yard versus a horse chestnut, but the same issues with toxicity would apply. Although the information has been hard to track down, it looks as though the few sources I found do suggest that both are self-pollinating and I would be interested if others have additional information on this. One way to tell for sure is if you only have one tree and are pretty sure that there are no neighboring
trees of the same type around, then if it is setting abundant nuts, it probably is self-fertile. Given this possibility, it seems that one might be able to select for reduced toxicity if mutations in the biosynthetic pathway were to accumulate. For the reasons indicated below, this variant selection may unfortunately have reduced vigor and resistance to pests and diseases.
It's likely that the toxicity contributes to the wide distribution and prolific output of the nuts on these trees. There appears to be evidence that the toxins deter insect predation as well as possess anti-microbial activity for resisting pathogen attack. Despite all of this, there are several reports of the use of the processed nuts by
Native Americans (linked below). It would be interesting to know just how much of this knowledge for processing the nuts to edibility still exists....I hesitate to try this on my own without some pretty good advice before hand. Would be interested to know if others have any knowledge or information on the matter.
https://www.arborday.org/programs/nationaltree/buckeye.cfm
https://www.reference.com/food/can-eat-buckeye-nuts-ac31d3cb9daabe5c
http://www.uky.edu/hort/Yellow-Buckeye