What Are Horse Chestnut Conkers?

Horse chestnut conkers are the fruit of the horse chestnut tree, Aesculus hippcastanum. These large seeds are not true chestnuts and are not edible by either horses or humans, despite the tree’s name. Conkers are often used to play a game named after them, where players knock the seeds together. Ohio buckeyes, a close relative of the horse chestnut, produce similar seeds that are sometimes used in the game.

The name horse chestnut comes from the small, horseshoe-shaped mark left by detached leaves. In earlier history, some people fed conkers to horses, believing it would make their coats shiny or cure chest complaints. Horse chestnut conkers contain a poison called esculin, which can be fatal if ingested. Chestnut extract taken from the seed is safe, as the poison is removed and leaves a substance called aescin, used to treat various circulatory disorders. During the two world wars, they were used to create acetone for use in military armaments, and have also been processed to whiten cloth.

Horse chestnut conkers ripen in the fall like regular chestnuts in a prickly outer shell. When they fall from the tree, the shell cracks to reveal the seeds. In England fall is the prime season for harvesting conkers to play the game, and payers look for large, symmetrical seeds. If stored in a dry place for up to a year, they will become very hard. In North Dakota in the US, the game is called "Kingers" and is usually played with Ohio buckeyes.

To begin a game of horse chestnut conkers, players must drill a hole in the middle of their seeds and thread a string through. They then tie a knot in the bottom of the string so the conker hangs from it. The string should be long enough to wind around the hand and leave about ten inches dangling down. Players then take turns hitting opponents' conkers until one of them breaks; the one whose game piece remains intact is the winner.

One player holds the conker out dangling from the string, and must keep it completely still. The other player draws the active conker back and tries to knock the other one as hard as possible. If he misses, he gets two more tries. Rapped knuckles are common, and the conkers can even fly up and hit players in the face.

In Britain where the tree is very common, serious horse chestnut conkers competitions are held yearly. There are very strict rules regarding the treatment of the game pieces. Soaking the seed in vinegar or baking it in the oven will harden it, making it more likely to break opponent’s conkers. These methods as well as using an old dried conker are considered cheating; many competitions provide conkers and laces to avoid any illegal activity.