Editing Ochroma

{{Short description|Genus of trees}}
{{Redirect|Balsa}}
{{Speciesbox
|image = Ochroma pyramidale Maui.jpg
|image_caption = ''Ochroma pyramidale'' at the Large Tree Habitat at [[Tropical Gardens of Maui]], [[Iao Valley]] Road, [[Maui]], [[Hawaii]], United States
|display_parents = 2
|genus = Ochroma
|parent_authority = [[Olof Swartz|Sw.]]
|species = pyramidale
|authority = ([[Antonio José Cavanilles|Cav.]] ex [[Jean-Baptiste Lamarck|Lam.]]) [[Ignatz Urban|Urb.]]<ref name="TPL Ochroma" />
|synonyms = ''Bombax pyramidale'' <small>Cav. ex Lam.</small><br />
''Ochroma bicolor''  <small>Rowlee</small><br />
''Ochroma concolor'' <small>Rowlee</small><br />
''Ochroma lagopus'' <small>Sw.</small><br />
''Ochroma obtusum'' <small>Rowlee</small>
|synonyms_ref = <ref name="GRIN">{{GRIN | access-date=26 October 2009}}</ref>
}}

'''''Ochroma pyramidale''''', commonly known as the '''balsa tree''', is a large, fast-growing [[tree]] native to the Americas. It is the sole member of the [[genus]] '''''Ochroma'''''.<ref name="TPL Ochroma">{{ cite web | title = Search results for ''Ochroma'' | work = The Plant List | url = http://www.theplantlist.org/tpl1.1/search?q=Ochroma | access-date = 1 March 2016 }}</ref> The tree is famous for its wide usage in [[woodworking]], due to its softness and its high strength compared to its low density. The name ''balsa'' is the Spanish word for "raft"<ref>[http://www.oed.com/view/Entry/15041 "balsa, n.". OED Online. March 2013. Oxford University Press. 9 May 2013]</ref> and the Portuguese word for [[ferry]].

A deciduous [[angiosperm]], ''Ochroma pyramidale'' can grow up to 30&nbsp;m tall, and is classified as a [[hardwood]] despite the wood itself being very soft; it is the softest commercial hardwood and is widely used because of its light weight.

Balsa trees grow extremely fast, often up to 27 metres in 10–15 years, and do not usually live beyond 30 to 40 years. They are often cultivated in dense patches, with Ecuador supplying 95% or more of the commercial balsa. The wood from these trees is highly valuable due to its high strength-to-weight ratio, which is achieved through a kiln-drying process that leaves the wood's cells hollow and empty.

Balsa wood is popular for light, stiff structures in model bridge tests, model buildings, and construction of model aircraft. It is also used in the manufacturing of wooden crankbaits for fishing, makeshift pens for calligraphy, composites, surfboards, boats, "breakaway" props for theatre and television, and even in the floor pans of the [[Chevrolet Corvette]]. Balsa wood played a historical role in Thor Heyerdahl's [[Kon-Tiki expedition]] where it was used to build the raft. Balsa wood is also popular in arts such as whittling, and in the making of baroque-style picture frames due to its ease of shaping.

== Biology ==
[[file:Ochroma pyramidalis MS 3425.jpg|thumb|right|Balsa on [[Bota Hill]], [[Limbe Botanical Garden]], [[Cameroon]]]]

A member of the mallow family, ''Ochroma pyramidale'' is native from southern Mexico to southern Brazil, but can now be found in many other countries (Papua New Guinea, Indonesia, Thailand, Solomon Islands). It is a [[Pioneer species|pioneer plant]], which establishes itself in clearings in forests, either man-made or where trees have fallen, or in abandoned agricultural fields. It grows extremely rapidly, up to {{convert|27|m}} in 10–15 years. The speed of growth accounts for the lightness of the wood, which has a lower density than [[Cork (material)|cork]]. Trees generally do not live beyond 30 to 40 years.<ref name=AngierZiegler2011>{{Cite journal|last1=Angier|first1=N.|last2=Ziegler|first2=C.|year=2011|title=Treetop happy hour|journal=National Geographic|volume=219|issue=5|pages=130–143|name-list-style=amp}}</ref>

Flowers are produced from the third year onwards, typically at the end of the rainy season when few other trees are in flower. The large flowers,  up to twenty cm (eight inches) in diameter,<ref>{{cite book | last1= Condit | first1= Richard |last2= Perez | first2= Rolando | last3= Daguerre | first3= Nefertaris | date= 2011 | title= Trees of Panama and Costa Rica | location= Princeton, N.J. | publisher= Princeton Univ. Press | pages=276-277 | ISBN = 978-0-691-14710-9 }}</ref> open in the late afternoon and remain open overnight. Each may contain a pool of nectar up to {{convert|2.5|cm}} deep. Daytime pollinators include [[capuchin monkey]]s. However, most pollination occurs at night. The main pollinators were once thought to be bats, but recent evidence suggests that two nocturnal arboreal mammals, the [[kinkajou]] and the [[olingo]], may be the primary pollinators.<ref name=AngierZiegler2011/>

It is [[evergreen]] or dry-season [[deciduous]], with large {{convert|30|to|40|cm}}, weakly [[Leaf shape|palmately]] lobed leaves.

Being a deciduous [[angiosperm]], balsa is classified as a [[hardwood]] despite the wood itself being very soft; it is the softest commercial hardwood.

== Cultivation ==

[[Ecuador]] supplies 70% or more of commercial balsa. In recent years, about 60% of the balsa has been [[plantation]]-grown in densely packed patches of around 1000 trees per hectare (compared to about two to three per hectare in nature). The trees are harvested after six to ten years of growth in Ecuador. The remaining volume of balsa is harvested from plantations in Papua New Guinea; the climate is different, therefore harvesting occurs at 4-5 years of age.

== Uses ==
[[File:Balsa.jpg|thumb|left|Three different sizes of balsa wood stock]]

Balsa [[lumber]] is very soft and light, with a coarse, open [[Wood grain|grain]]. The [[density]] of dry balsa [[wood]] ranges from 40 to 475&nbsp;kg/m<sup>3</sup>, with a typical density around 160&nbsp;kg/m<sup>3</sup>.<ref>Terry Porter: "Wood Identification and Use", page 160. Guild of Master Craftsman Publications Ltd. 2004</ref><ref>{{cite web |title=Balsa {{!}} WoodSolutions |url=https://www.woodsolutions.com.au/wood-species/hardwood/balsa |website=www.woodsolutions.com.au}}</ref><ref name="Borrega">{{cite journal |last1=Borrega |first1=Marc |last2=Ahvenainen |first2=Patrik |last3=Serimaa |first3=Ritva |last4=Gibson |first4=Lorna |title=Composition and structure of balsa (Ochroma pyramidale) wood |url=https://link.springer.com/article/10.1007/s00226-015-0700-5 |journal=Wood Science and Technology |pages=403–420 |language=en |doi=10.1007/s00226-015-0700-5 |date=1 March 2015|volume=49 |issue=2 |hdl=1721.1/102327 |s2cid=6546811 |hdl-access=free }}</ref> Balsa is the softest wood ever measured using the [[Janka hardness test]] (22 to 167 [[pound (force)|lbf]]).<ref name= balsa_quipo_1955>{{cite report |title=Strength and related properties of Balsa and Quipo woods |date= November 1955 |publisher=UISDA Forest Service, Forest Products Laboratory |last1=Wiepking |first1= C. A. |last2= Doyle |first2=D. V. |url= http://ir.library.oregonstate.edu/xmlui/handle/1957/1239 |id= Report No. 1511 |pages=27–28}}</ref> The wood of the living tree has large cells that are filled with water. This gives the wood a spongy texture. It also makes the wood of the living tree not much lighter than water and barely able to [[Buoyancy|float]]. For commercial production, the wood is kiln-dried for about two weeks, leaving the cells hollow and empty. The large volume-to-surface ratio of the resulting thin-walled, empty cells gives the dried wood a large strength-to-weight ratio because the cells are mostly air. Unlike naturally rotted wood, which soon disintegrates in the [[rainforest]]s where balsa trees grow, the cell walls of kiln-[[Wood drying|seasoned]] balsa wood retain their strong structure of [[cellulose]] and [[lignin]].<ref name="Balsa Wood uses">{{cite web|title=Balsa Wood description |url=http://www.cds.ed.cr/teachers/harmon/page21.html |access-date=2011-01-02 |url-status=dead |archive-url= https://web.archive.org/web/20101122130918/http://www.cds.ed.cr/teachers/harmon/page21.html |archive-date=November 22, 2010 }}</ref>

Because it is low in density but high in specific strength (strength per weight), balsa is a very popular material for light, stiff structures in [[balsa wood bridges|model bridge tests]], model buildings, and construction of [[model aircraft]]; all grades are usable for airworthy [[control line]] and [[radio-controlled aircraft]] varieties of the aeromodeling sports, with the lightest "contest grades" especially valuable for [[Free flight (model aircraft)|free-flight model aircraft]]. However, it is also valued as a component of full-sized light wooden [[aeroplane]]s, most notably the [[World War II]] [[de Havilland Mosquito]].<ref name="Balsa Wood uses" />

Balsa is used to make wooden [[Plug (fishing)|crankbaits]] for fishing, especially [[Rapala]] lures.

Sticks of dried balsa are useful as makeshift pens for [[calligraphy]] when commercial metal nibs of the desired width are not available.<ref>{{cite book |last1=Lovett |first1=Patricia |author1-link=Patricia Lovett |title=Calligraphy and Illumination A History and Practical Guide |date=2000 |publisher=[[British Library]] |location=London |isbn=9780810941199 |page=14}}</ref>

Balsa wood is often selected as a core material in [[Composite material|composites]]. Because O. pyramidale grows quickly and tolerates poor soils it is lower in cost per performance compared to polymer foams like [[Polystyrene|EPS]] while having better tensile strength than typical foams. For example, the blades of [[wind turbine]]s are commonly constructed of many balsa plywood cores and internal spars covered with resin infused cloth on both sides. In [[table tennis]] rackets, a balsa layer is typically sandwiched between two pieces of thin [[plywood]] made from other species of wood. Balsa wood is also used in [[laminate]]s together with [[glass-reinforced plastic]] ([[fiberglass]]) for making high-quality balsa [[surfboard]]s and for the [[deck (ship)|decks]] and topsides of many types of [[boat]]s, especially pleasure craft less than 30&nbsp;m in length. On a boat, the balsa core is usually [[Wood grain|end-grain]] balsa, which is much more resistant to compression than if the soft balsa wood were laid lengthwise.

More than 90% of the world's Balsa wood volume is prepared into end grain panels for the composites industry, mostly used as structural cores in the wind turbine blades. Where strength, rigidity, durable and environmentally sustainable materials are sought after. 

Balsa is also used in the manufacture of "breakaway" wooden props such as tables and chairs that are designed to be broken as part of theatre, movie, and television productions.

The [[Chevrolet Corvette (C5)|fifth]] and [[Chevrolet Corvette (C6)|sixth]] generations of the [[Chevrolet Corvette]] had [[floor pan]]s composed of balsa sandwiched between sheets of [[carbon-fiber-reinforced plastic]].<ref name="Balsa Wood uses"/>

Norwegian scientist and adventurer [[Thor Heyerdahl]], convinced that early contact between the peoples of [[South America]] and [[Polynesia]] was possible, built the raft ''[[Kon Tiki]]'' from balsa logs, and upon it his crew and he sailed the [[Pacific Ocean]] from [[Peru]] to the Polynesian [[Tuamotus|Tuamotu Archipelago]] in 1947. However, the ''Kon Tiki'' logs were not seasoned and owed much of their (rather slight) buoyancy to the fact that their sap was of lower density than sea water. This [[Serendipity|serendipitously]] may have saved the expedition, because it prevented the seawater from [[Wiktionary:waterlog|waterlogging]] the wood and sinking the raft.<ref name="Heyerdahl2013">{{cite book|author=Thor Heyerdahl|title=Kon-Tiki: Across the Pacific by Raft|url=https://books.google.com/books?id=g0mDAgAAQBAJ|date=24 December 2013|publisher=Skyhorse Publishing Company, Incorporated|isbn=978-1-62914-634-8}}</ref>

Balsa wood is also a popular wood type used in the arts of [[whittling]],<ref name="Balsa Wood uses"/> and [[Surfboard#Construction|surfing]]. In the making of picture frames, balsa was often used in a baroque style because of the ease of shaping the design.

In parts of Africa and south America the leaves of the balsa tree are used to enhance the traditional [[Gold panning|panning]] method of extracting gold from ore. When mixed with water a soapy solution is produced and this helps the lighter, unwanted material to wash away.<ref>{{cite journal |title=Business Innovator: Felipe Arango, Colombia |journal=[[Americas Quarterly]] |date=24 July 2013 |url=https://www.americasquarterly.org/fulltextarticle/business-innovator-felipe-arango-colombia/ |publisher=[[Council of the Americas]] |location=New York}}</ref><ref>{{cite news |last1=Howe |first1=Marc |title=Colombia backs eco-friendly gold production |url=https://www.mining.com/colombia-backs-eco-friendly-gold-production-38172/ |access-date=19 November 2023 |work=Mining |publisher=[[Glacier Media]] |date=1 January 2013}}</ref>

== Gallery ==
<gallery>
file:Ochroma pyramidale1FrancesWHorne.jpg|Painting by Frances W. Horne from the [[Flora Borinqueña]]
file:Ochroma pyramidale Maui.jpg|''Ochroma pyramidale'' at [[Tropical Gardens of Maui]] [[Iao Valley]] Rd, [[Maui]]
file:Balsas_and_kayak.jpg|Two balsa rafts and a kayak at Lagos de Montebello in [[Chiapas, Mexico]]
file:Balsa airframe.jpg|Balsa construction in a "stick and tissue" [[Free flight (model aircraft)#Scale rubber|free-flight rubber scale]] model airplane
</gallery>

== See also ==
* ''[[Tilia]]'', another tree producing lightweight lumber (especially ''[[Tilia americana]]'') 
* ''[[Paulownia]]''

== References ==
{{Reflist}}

== External links ==
* {{Commons category-inline}}

{{Woodworking}}
{{Taxonbar|from1=Q12302824|from2=Q187941}}

[[Category:Bombacoideae]]
[[Category:Malvaceae genera]]
[[Category:Monotypic Malvales genera]]
[[Category:Plants described in 1920]]
[[Category:Trees of Northern America]]
[[Category:Trees of Central America]]
[[Category:Trees of Peru]]
[[Category:Trees of South America]]
[[Category:Trees of the Caribbean]]