Answer: Hickories are in the same family as walnut trees, and walnut leaves and roots contain a substance called juglone that inhibits the growth of other plants. I found no mention of this chemical associated with hickories, but it' s possible it may be a factor. However, it's also likely that the shade and dropped leaves/nuts have simply stunted the grass. As you see when you go into a wooded setting, few plants can survive directly under large trees.
I would first take a soil sample and have it tested. Your Cooperative Extension office (ph# 614-368-1925) should offer test kits. If the soil is fine, and you really want lawn under there, I would trim any low branches that shade the area, spread a very thin (1") layer of topsoil, and plant a grass seed mix developed for shady spots. If I were you, though, I think I would set a nice park bench under the tree, bring out a glass of lemonade, and forget about the lawn!
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