A stroll through the park reveals autumn at its brilliant peak this month. As brisk air and rich hues of crimson, orange and yellow carry you away, you might hear a familiar thud.

The fall of the spiky-shelled chestnut is a sound synonymous with the season.

For an ever-growing number of adventurous consumers, fall harvest is prime time for urban foraging. And this month, you might be tempted to forage one of autumn’s most familiar offerings: chestnuts.

But before you do, know what you’ve gathered before it finds its way into the oven.

Horse chestnuts (Neil Giardino/KPLU)

Horse chestnuts (Neil Giardino/KPLU)

Horse chestnuts, conker trees, buckeyes—call them what you like; just don’t call them true American chestnuts. Aesculus hippocastanum by their Latin designation, these natives of the mountainous slopes of the eastern Balkan forests are only distant relatives of the true chestnut tree.

The tree’s common name is a misnomer. Although the horse chestnut’s fruit bears a likeness to its good-natured cousin, the true American chestnut, the horse chestnut’s seed, or conker, is poisonous. Telltale signs of a thorough poisoning, which include vomiting, stomach irritation, and abdominal pain, typically manifest within 16 hours of intake of the nut or its juice. Its toxicity is on account of alkaloid saponins, and curiously enough, the deer is one of the only known mammals that can safely consume this poisonous chemical compound.

So how do you tell if the chestnut trees in your neighborhood are fruiting a toxic nut? For starters, the edible variety always has a pointed tip. Its toxic relative bears no such pointed end on its brown shell.

Edible chestnuts have a pointed end. (Drift Words/Flickr)

Edible chestnuts have a pointed end.
(Drift Words/Flickr)

And Mark Mead, senior urban forester of Seattle Parks and Recreation, offers this pointer on how to identify a horse chestnut tree: “With horse chestnuts you’ll see a row of them, whereas with true chestnuts you’ll usually see two, maybe three.”

If Mother Nature’s tip-off isn’t enough to deter you from bringing the toxic horse chestnut home to roast, Mead offers one more clue, and it’s a dead giveaway: “Basically the horse chestnuts are really bitter, where as the true chestnut is buttery. And you can tell from its oil content.”

Taste receptors in humans once served as evolutionary defenses, helping to identify vital nutrients and toxins in plants. Extreme bitterness in taste remains a biological red flag, warning, in this case, of the horse chestnut’s poison.

While true chestnuts are few and far between in the Puget Sound area these days, they can still be found on the statelier boulevards of some Seattle neighborhoods. On one broad street atop Seattle’s Queen Anne hill, a few majestic old chestnut trees are dropping edible seeds this time of year. And don’t forget: it’s polite to ask before you forage.

Neil Giardino is an intern for KPLU News. 

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4 Responses

  1. Catherine

    So, which has the ‘pointed end’…the tree-top, the seed or the spikey outer covering? I’d like to be able to discern poisonous from non-poisonous without taste-testing! 😉

    • Martha Kang

      Ah, the pointed end is visible on the chestnut’s brown shell. We’ve added a photo to help differentiate.

  2. Carole Miller

    Novice to this submit/reply format, what does “comment is awaiting moderation” mean? Carole

    • Steve

      Carole, comment awaiting moderation means a post to the comment section needs to be approved by a website/comment section moderator before it can be publicly seen, it helps avoid spam and inflammatory remarks