A tree may explode when stresses in its trunk increase due to extreme cold, heat, or

lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average ...

, causing it to split suddenly.

Causes

Cold

Cold weather will cause some trees to shatter by freezing the sap, because it contains water, which expands as it freezes, creating a sound like a

gunshot A gunshot is a single discharge of a gun, typically a man-portable firearm, producing a visible flash, a powerful and loud shockwave and often chemical gunshot residue. The term can also refer to a ballistic wound caused by such a discharg ...

. The sound is produced as the tree bark splits, with the wood contracting as the sap expands.

John Claudius Loudon John Claudius Loudon (8 April 1783 – 14 December 1843) was a Scottish botanist, garden designer and author. He was the first to use the term arboretum in writing to refer to a garden of plants, especially trees, collected for the purpose of ...

described this effect of cold on trees in his ''Encyclopaedia of Gardening'', in the entry for frosts, as follows:

Henry Ward Beecher Henry Ward Beecher (June 24, 1813 – March 8, 1887) was an American Congregationalist clergyman, social reformer, and speaker, known for his support of the abolition of slavery, his emphasis on God's love, and his 1875 adultery trial. His r ...

records anecdotal evidence of the wood from which instrument cases and carrying boxes were splitting in temperatures of in Captain Bach's travels near the

Great Slave Lake Great Slave Lake (french: Grand lac des Esclaves), known traditionally as Tıdeè in Tłı̨chǫ Yatıì (Dogrib), Tinde’e in Wıìlıìdeh Yatii / Tetsǫ́t’ıné Yatıé (Dogrib / Chipewyan), Tu Nedhé in Dëne Sųłıné Yatıé (Chi ...

. Linda Runyon, author of books on wilderness living, recounts her experience of the effect of cold on maple trees as follows: Wally and Shirley Loudon reported the effect of the freeze of December 1968 upon their orchard in

Carlton, Washington Carlton the "Mediterranean of the Methow" is an unincorporated community in Okanogan County, Washington, United States. Carlton is located on the Methow River and Washington State Route 153, south of Twisp. Carlton has a post office with ZIP c ...

as follows: To the

Sioux The Sioux or Oceti Sakowin (; Dakota: /otʃʰeːtʰi ʃakoːwĩ/) are groups of Native American tribes and First Nations peoples in North America. The modern Sioux consist of two major divisions based on language divisions: the Dakota and ...

The Dakotas The Dakotas is a collective term for the U.S. states of North Dakota and South Dakota. It has been used historically to describe the Dakota Territory, and is still used for the collective heritage, culture, geography, fauna, sociology, econo ...

and the

Cree The Cree ( cr, néhinaw, script=Latn, , etc.; french: link=no, Cri) are a North American Indigenous people. They live primarily in Canada, where they form one of the country's largest First Nations. In Canada, over 350,000 people are Cree o ...

, the first new moon of the new year is known, in various dialects, as the "Moon of the Cold-Exploding Trees". Tree sap is a supercooled liquid in cold temperatures. John Hunter observed, in his ''Treatise on the Blood'', that tree sap within a tree freezes some 17 degrees Fahrenheit below its nominal freezing point.

Lightning

Trees can explode when struck by lightning. The strong

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...

is carried mostly by the water-conducting sapwood below the

bark Bark may refer to: * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, e ...

, heating it up and boiling the water. The pressure of the steam can make the trunk burst. This happens especially with trees whose trunks are already dying or rotting. The more usual result of lightning striking a tree, however, is a lightning scar, running down the bark, or simply root damage, whose only visible sign above ground is branches that were fed by the root dying back.

Fire

Exploding trees may occur during a wildfire, but there is apparently no evidence of this. The myth of exploding trees may have originated with a classic film about wildfires, ''

Red Skies of Montana ''Red Skies of Montana'' is a 1952 adventure drama film in which Richard Widmark stars as a smokejumper who attempts to save his crew while being overrun by a forest fire, not only to preserve their lives, but to redeem himself after being the o ...

'', which showed firefighters witnessing exploding trees, based on special effects.

April Fools’ Day hoax

Exploding trees were the subject of a 2005

April Fools' Day April Fools' Day or All Fools' Day is an annual custom on 1 April consisting of practical jokes and hoaxes. Jokesters often expose their actions by shouting "April Fools!" at the recipient. Mass media can be involved in these pranks, which may ...

hoax in the United States, covered by

National Public Radio National Public Radio (NPR, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from other n ...

, stating that

maple ''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since h ...

trees in

New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York to the west and by the Canadian provinces ...

had been exploding due to a failure to collect their sap, causing pressure to build from the inside. The

root pressure Root pressure is the transverse osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves. Root pressure occurs in the xylem of some vascular plants when the soil moisture level is high eithe ...

in a maple tree is approximately 0.1

MPa MPA or mPa may refer to: Academia Academic degrees * Master of Performing Arts * Master of Professional Accountancy * Master of Public Administration * Master of Public Affairs Schools * Mesa Preparatory Academy * Morgan Park Academy * Mou ...

, one standard atmosphere, which is insufficient to cause a tree to explode.

Footnotes

* Similar text can be found in the entry for Frost in

Charles Hutton Charles Hutton FRS FRSE LLD (14 August 1737 – 27 January 1823) was a British mathematician and surveyor. He was professor of mathematics at the Royal Military Academy, Woolwich from 1773 to 1807. He is remembered for his calculation of the ...

's 1795 ''Mathematical and Philosophical Dictionary''

References

External links

YouTube video with cold weather and bursting tree bark
at 43:53, Wild Russia, Episode 6, Primeval Valleys {{DEFAULTSORT:Exploding Tree

Tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

Trees