Horse Chestnut vs. Sweet (Edible) Chestnut

HORSE CHESTNUT (Aesculus) seeds are TOXIC — nausea, vomiting, worse.

The tell: Sweet chestnut (Castanea): long toothed single leaves, very spiny burs, pointed nuts with a tassel. Horse chestnut: PALMATE compound leaves (fingers from a palm), less-spiny husks, round smooth 'conkers.'

Rule: Palmate leaves + round conkers = not food.