Horse Chestnut

Basic Information
Tree ID: 
9
Family: 
Sapindaceae
Genus and species: 
Aesculus hippocastanum
Description: 
The horse chestnut is a shade and ornamental tree with an upright elliptical shape. It is native to southeast Europe (particularly the Pindus mountains mixed forests and the Balkan mixed forests of the Balkan peninsula), but it was introduced into other parts of Europe as well as North America. The horse chestnut is easily grown from seed and tolerates city life well, which is why it is often planted along streets (Little 1980; "Herbs at a Glance", 2008). This particular horse chestnut is the gateway to the Marsh Botanical Gardens, which is just down the hill from this tree. It has a lovely view of sunset through the many other beautiful trees in the area.
Location
Area: 
Marsh and Farnam Gardens
Collected Data
Tree shape: 
upright ellipse
Date of tree entry: 
02/05/2014
Bark
The bark is thin, smooth, and well fissured. It is gray or brown in color (Little 1980).
Twigs & branches
The twigs are light brown, stout, and have large, black sticky buds at the tips (Little 1980).
Foilage
The leaves of the horse chestnut are palmately compound with either five or seven leaflets spreading like fingers. Each individual leaflet is saw-toothed and elliptical in shape, tapering to a petiolule-less base (a petiolule is the stalk that attaches the leaflets to the leaf--petiolule is to leaflet as petiole is to leaf). The leaves are light green when they first start to grow, but as they reach maturity they become darker on top and remain lighter on the underside. In autumn, the leaves turn yellow (Little 1980).
Reproductive Structures
The horse chestnut's flowers are usually one inch (1" or 2.5 cm) in length, and have a narrow bell-shape. They are typically found in upright branched clusters, or panicles, approximately ten inches (10" or 25cm) in length (Little 1980). These clusters are popularly called "candles" in the UK because they seem to "light up the tree" ("The Woodland Trust"). Each individual flower has four or five white, fringed petals with red and yellow spots near the base (Little 1980). The horse chestnut has perfect flowers, meaning that each flower has both male and female reproductive parts ("The Woodland Trust").
Fruit
The horse chestnut's fruit is colloquially called a "conker" and refers to the shiny brown, poisonous seed that is protected by a green spiny capsule ("Kew royal botanical"). The capsule is 2-2 1/2" (5-6 cm) in diameter and splits into two or three parts to reveal one or two conkers inside (Little 1980). The conkers often have a whitish scar at the base. Conkers appear in September and fall to the ground as they ripen ("Horse chestnut (aesculus hippocastanum)"). Although conkers are poisonous for most animals when ingested, some mammals, particularly deer, are able to digest them safely ("The Woodland Trust"). Despite it being poisonous, the conker is famous for its medicinal uses as well as its starring role in the classic schoolyard game of Conkers.
Seasons
  • Horse chestnut in spring
  • Horse chestnut in summer
  • Horse chestnut in winter
Research
Natural range of distribution: 
Habitat: 
The horse chestnut is native to the mixed forests of the Pindus mountains of Greece and Balkan Peninsula (including Albania, Macedonia and part of Eastern Bulgaria) but has been introduced in many urban and suburban settings, particularly in parks, large gardens, and along streets ("Horse chestnut (aesculus hippocastanum)"). The map above shows in purple the areas in Europe of introduced horse chestnuts trees (non-cultivated) and in yellow the areas where native horse chestnuts still grow (the red area is part of the native range where horse chestnuts no longer grow). The horse chestnut can grow in a variety of soils, although it prefers rich moist soils ("Horse chestnut", Little 1980).
Origin, history, and uses: 

Origin
The horse chestnut is native to the Balkan peninsula in southeast Europe, and in particular the Pindus mountains mixed forests and the Balkan mixed forests (Little 1980; “Herbs at a Glance”, 2008).

History
In the 1600s, the horse chestnut was introduced in Britain, and from there eventually spread to the rest of Europe and North America (“The Woodland Trust”).

The beloved game of Conkers got its start in the late 1700s. It was developed from a similar game called “Conquerors” which was played with hazelnuts, cobnuts, or snail shells. Soon, children throughout England and Ireland were playing Conkers in school yards, developing the game and adding rules as they went along.

During both World War I and World War II, the British government called for a collection of conkers because they serve as a source of acetone, which is used to make cordite, which is then used in military armaments. The government offered monetary rewards for a given weight of conkers collected (“Conkers - Collected for Use in Two World Wars”).

In 1965, two men got a group together after they had been drinking at a local bar, and they held the very first ever World Conker Championships, which are now held every year at the Ashton Conker Club (“The History of Ashton Conker Club”).

Uses
Extract from the horse chestnut seed has been used both orally and topically to treat hemorrhoids and chronic venous insufficiency (CVI), a condition in which the veins do not sufficiently pump blood from the legs back to the heart. The active ingredient is usually 16-20% aescin. There is some evidence that suggests aescin is even more effective in treating CVI than the standard treatment, wearing compression socks. There is no evidence supporting its use in treating other conditions. If the extract is not properly processed, the poisonous compound esculin gets left behind. Thus, homemade treatments are not recommended (“Herbs at a Glance”, 2008).

Conkers have long been used to repel spiders, but whether or not they actually repel spiders is still being debated. Some argue that the conkers themselves don’t repel spiders, but that the conkers repel other insects that serve as the spiders’ source of food. Alternatively, the time of year at which conkers fall could just align with the disappearance of spiders and the onset of colder weather (Royal Society of Chemistry). The conkers are also used in wardrobes to ward against moths (“All About Conkers”).

The horse chestnut’s timber is not used commercially because it it too weak. However, its smooth texture and pale creamy white color make it ideal for carving (“The Woodland Trust”).

Aesculus hippocastanum​ is also a favorite subject for bonsai, the Japanese art form involving growing miniature versions of trees in a pot (“Bonsai Training Guide”).

Phenology: 
When the horse chestnut is young, its bark is a smooth pinky grey ("The Woodland Trust"). As the tree matures, the bark darkens and develops a scalier, more fissured texture ("The Woodland Trust"). Each year, the horse chestnut produces sticky black buds in the spring, which eventually become the clusters of white flowers seen in late spring, usually from April to mid-May. Those flowers, once pollinated by insects, each develop into a conker with a spiky green shell. The conkers reach maturity in late summer/early autumn and fall to the ground in autumn ("The Woodland Trust", "Horse chestnut (aesculus hippocastanum)", Little 1980). When the leaves of the horse chestnut first appear in spring, they are light green. However, as they reach maturity they become darker on top. In autumn, the leaves turn yellow (Little 1980). The horse chestnut can live up to 300 years, provided it does not become infected with one of the many fungal diseases and other health conditions to which the horse chestnut is susceptible. These include bleeding canker, which can cause their death; Guignardia leaf blotch; and horse chestnut scale insect. The horse chestnut leaf miner can also do the trees some damage, but it is usually not significant. The leaf miner simply causes the leaves to turn brown and fall early, but this happens so late in the season that it rarely has any effect on the tree's wellbeing ("The Woodland Trust").
References: 

Aesculus hippocastanum. The ICUN Red List of Threatened Species. Accessed September 8, 2014. http://www.iucnredlist.org/details/202914/0

All About Conkers. (n.d.). All About Conkers. Retrieved from http://www.worldconkerchampionships.com/html/conkers_about.html.

Anne Frank Organizations, “The Sapling Project.” Accessed February 11, 2014. http://annefrank.com/the-sapling-project/.

Bonsai Training Guide for Aesculus hippocastanum by Ma-Ke Bonsai. (n.d.). Bonsai Training Guide for Aesculus hippocastanum by Ma-Ke Bonsai. Retrieved from http://guide.makebonsai.com/bonsai_species_guide_training.asp?SpeciesID=…

Conkers - Collected for Use in Two World Wars [Radio series episode]. In Making History. Sue Cook.

Frank, A. (1995). The Diary of a Young Girl ( ed.). New York: Bantam Doubleday Dell Publishing Group Inc.

Herbs at a Glance. (June 2008) National Center for Complementary and Alternative Medicine, National Institute of Health Department of Health and Human Services.

Horse chestnut (aesculus hippocastanum). (n.d.). Retrieved from http://www.arkive.org/horse-chestnut/aesculus-hippocastanum/image-A16592…

Horse chestnut. (n.d.). Retrieved from http://www.arborday.org/treeguide/treeDetail.cfm?ID=256

Horse chestnut. (n.d.). The Woodland Trust. Retrieved from http://www.woodlandtrust.org.uk/learn/british-trees/non-native-trees/hor…

Kew royal botanical gardens: Horse chestnut. (n.d.). Retrieved from http://apps.kew.org/trees/?page_id=98

Kiev’s Spectacular Horse Chestnut Trees. (n.d.). Retrieved from http://www.ukraine.com/blog/kiev-s-spectacular-horse-chestnut-trees

Lack, H. (2000). The discovery and rediscovery of the horse chestnut. Curtis’s Botanical Magazine, 17(2), 109-137. Retrieved from http://arnoldia.arboretum.harvard.edu/pdf/articles/628.pdf

Little, E. L., & Bullaty, S. (1980). Horsechestnut. The Audubon Society field guide to North American trees (Chanticleer Press ed., ). New York: Knopf : distributed by Random House.

Royal Society of Chemistry. (n.d.). The Reaction News and events RSS. Retrieved from http://www.thereaction.net/news/y2010/m10/spiders_versus_conkers_definit…

The History of Ashton Conker Club. (n.d.). History of the World Conker Championships. Retrieved from http://www.worldconkerchampionships.com/html/conkers_history.html

More
Other information of interest: 

Originally called the “wild chestnut”, the horse chestnut got its name from the misguided belief that feeding the fruit to horses could relieve them of chest pain. In reality, it is poisonous to horses and causes them to have tremors. Additionally, the horse chestnut is only distantly related to the chestnut trees (Lack 2000). So it turns out “horse chestnut” was about as wrong of a name as possible for this tree! But perhaps its many uses and literary references have helped it to see beyond its identity crisis.

The beautifully distinctive, sweet-smelling flowers of the horse chestnut tree serve as a symbol of the city of Kiev, Ukraine where horse chestnuts are abundant. The trees came into popularity in the early nineteenth century, when city planners started planting them along streets and throughout parks. They can be found at the Orthodox monastery of Pechersk Lavra, as well as at the Kiev botanical gardens. Although pollution can reduce the horse chestnut’s lifespan from hundreds of years to just one hundred years, there are a few in Kiev that have been around since the early 1800s, blooming each year so visitors and residents alike can enjoy their beautiful flowers (“Kiev’s Spectacular Horse-Chestnut Trees”).

The Anne Frank Tree

In Anne Frank’s The Diary of a Young Girl, she describes a horse chestnut tree that resided in the center of Amsterdam, writing, “Nearly every morning I go to the attic to blow the stuffy air out of my lungs, from my favorite spot on the floor I look up at the blue sky and the bare chestnut tree, on whose branches little raindrops shine, appearing like silver, and at the seagulls and other birds as they glide on the wind. As long as this exists, I thought, and I may live to see it, this sunshine, the cloudless skies, while this lasts I cannot be unhappy” (Frank).

In 2010, the tree fell in a storm after it had been weakened for many years by disease. It was estimated to be between 150 and 170 years old. Several saplings were prepared in the years leading up to the tree’s death, eleven of which have been distributed throughout the United States. The saplings can be found at the White House; the Children’s Museum of Indianapolis where the saplings were originally quarantined upon entry into the U.S.; Sonoma State University in California; Southern Cayuga School District in New York; the Washington State Holocaust Resource Center; Boston Common; the Holocaust Memorial Center in Farmington Hills, Michigan; the Idaho Anne Frank Human Rights Memorial; the William J. Clinton Presidential Center in Arkansas; and Liberty Park at Ground Zero in New York City, which commemorates the 9/11 terrorist attacks (“Sapling Project”).

The Honorable Game of Conkers

How to play:
The rules for preparing a conker and playing Conkers varies between the playground and the World Championships. For the World Championships, players are forbidden to bring their own conkers for fear that they would cheat by hardening their conkers through a number of techniques. This is considered cheating, and while it is permissible in the schoolyard, the World Championships attempt to keep a level playing field by providing conkers for all participants (“All About Conkers”).

Preparing your own conker:
Choose a conker that is big, round (as symmetrical as possible), and shiny (indicative of health). Drill a hole through the middle of the conker with a skewer or a similar device, being very careful as you do so not to harm the conker or your hand. Thread a piece of string through the hole and tie a knot at the end. The string should be long enough that when it is wrapped twice around your hand there are still approximately 10 inches (25 cm) left for the conker to hang down from your hand (“All About Conkers”).

Hardening techniques (“All About Conkers”):
  • soaking or boiling in vinegar or salt water
  • soaking in parafin
  • partially baking for about one half hour in the oven
  • coating with clear nail polish
  • filling with glue
  • storing in the dark for a year
Rules of play (on the playground): (note: the following rules were taken directly from the World Conker Championships’ website)
A coin toss usually decides who takes the first swing in Conkers, but on the playground this is more often a matter of whoever shouts “Obli, obli, oh, my first go” (or something similar) first. Each player has his or her conker on a knotted string. Players take turns hitting each other’s conker with their own. The player whose conker is to be hit first lets it hang down approximately 10 inches (25 cm) from the string which is wrapped round his hand. The player must hold it at the height his opponent chooses and he must hold it perfectly still. His opponent, the striker, wraps his conker string round his hand. He then takes the conker in the other hand and draws it back for the strike. Releasing the conker, he swings it down by the string held in the other hand and tries to hit his opponent’s conker with it. If he misses he is allowed up to two further goes. If the strings tangle, the first player to call “strings” or “snags” gets an extra shot. Players take alternate hits at their opponent’s conker. The game is won when one player destroys the other’s conker. If a player drops his conker or it is knocked from his hand, the other player can shout “stamps” and immediately stamp on the conker; but should its owner first shout “no stamps”, then “stamps” is disallowed and the conker (hopefully) remains intact (“All About Conkers”).
 
Rules of play (World Conker Championships): (note: the following rules were taken directly from the World Conker Championships’ website)
Competition rules do not allow “stamps”, while “snags” do not give an extra swing. In fact, causing snags is considered bad sportsmanship and can be grounds for disqualification. Full rules can be found here: http://www.worldconkerchampionships.com/html/conkers_rules.html
(“All About Conkers”).
 
Scoring:
In playground tournaments, each victory adds to a conker’s score. A conker who has one two battles, for example, is called a “two-er”. When a conker beats another conker, though, it absorbs the losing conker’s score. For example, if a “two-er” beat a “fiver”, it would become an “eight-er” (its two, the other conker’s five, and an additional one for the win over the “fiver”). As a result, winning conkers can quickly attain very large scores (“All About Conkers”).
Media and Arts