Day 361: How do you tell the difference between a horse chestnut (inedible, top) and an edible chestnut (bottom)? First of all, you should know that horse chestnuts belong to an entirely different genus (Aesculus) than true chestnuts (Castanea). However, certain physical similarities have given rise to the common name, and also are reflected in the taxonomy, i.e., Aesculus castanum (think "castanets," a term from the same root word). There are several different species of edible chestnut in the US, and since many are hybrids, I won't go farther than simply lumping them all together under "Castanea." The leaves of the horse chesnut tree are palmate, which is to say they are arranged like fingers on a hand. Those of true chestnuts are alternate, i.e., they are arranged along the stem singly, each leaf pointing away from the ones nearest it. The burr which encloses the nut is quite spiky in true chestnuts; horse chestnuts have fewer spines and look like the head of a mediaeval mace. The burrs of Aesculus (horse chestnut) split into halves, releasing a round "conker" from inside, as opposed to those of Castanea which split into twos or fours depending on species to reveal up to three nuts with pointed tips. Unfortunately, my description of edible chestnuts is going to have to end here because none of those I found beneath the trees had developed fully. All I could find were empty brown husks, no chestnuts to roast, sorry!
