The common English namehornbeam derives from the hardness of the woods (likened tohorn) and the Old Englishbeam, "tree" (cognate with Dutchboom and GermanBaum).
TheAmerican hornbeam is also occasionally known as blue-beech, ironwood, or musclewood, the first from the resemblance of the bark to that of theAmerican beechFagus grandifolia, the other two from the hardness of the wood and the muscled appearance of the trunk and limbs.
The botanical name for the genus,Carpinus, is the original Latin name for the European species, although someetymologists derive it from the Celtic for ayoke.[2]
Hornbeams are small, slow-growing,understory trees with a natural, rounded form growing 4.5–9 metres (15–30 feet) tall and wide; the exemplar species—theEuropean hornbeam—reaches a maximum height of 32 m (105 ft).[3]: 296
Leaves aredeciduous, dark-green, alternate and simple with a coarsely-serrated margin, varying from 3 to 10 centimetres (1 to 4 inches) in length. In autumn, leaves turn various shades of yellow, orange and red. Hornbeam saplings, stressed trees, and the lower branches of mature trees may exhibitmarcescence—where leaves wither with autumn butabscission (leafdrop) is delayed until spring.[4]
The smooth, gray trunk and larger branches of a mature tree exhibit a distinctive muscle-like fluting.[5]
As with other members of thebirch family, hornbeam flowers are wind-pollinated pendulouscatkins, produced in spring. Male and female flowers are on separate catkins, but on the same tree (monoecious). Female flowers give way to distinctive clusters of winged seeds that somewhat resemble the hops-like seeds of ironwood.[6]
The fruit is a smallnut about 3–6 millimetres (1⁄8–1⁄4 in) long, held in a leafybract; the bract may be either trilobed or simple oval, and is slightly asymmetrical. The asymmetry of the seedwing makes it spin as it falls, improvingwind dispersal. The shape of the wing is important in the identification of different hornbeam species. Typically, 10–30 seeds are on each seed catkin.[7][8]
Formerly some taxonomists segregated them with the generaCorylus (hazels) andOstrya (hop-hornbeams) in aseparate family,Corylaceae. Modern botanists placeCarpinus in the subfamilyCoryloideae of the familyBetulaceae.[9][10] Species ofCarpinus are often grouped into two subgeneraCarpinus subgenusCarpinus andCarpinus subgenus Distegicarpus.
The 43 species occur across much of thetemperate regions of the northern hemisphere, with the greatest number of species in east Asia, particularly China. Only three species occur in Europe, only one in eastern North America, and one inMesoamerica.[1][16][17][18][19]Carpinus betulus can be found in Europe, Turkey and Ukraine.[12]
Hornbeams yield a very hard timber, giving rise to the name "ironwood".[21] Driedheartwood billets are nearly white and are suitable for decorative use. For general carpentry, hornbeam is rarely used, partly due to the difficulty of working it.
The wood is used to construct carving boards, tool handles, handplane soles, coach wheels, piano actions, shoe lasts, and other products where a very tough, hard wood is required.
The wood can also be used as gear pegs in simple machines, including traditionalwindmills.[21] It is sometimescoppiced to provide hardwood poles. It is also used in parquet flooring and for making chess pieces.
^Gledhill D. 1985.The Names of Plants. Cambridge University PressISBN0521366755
^Stace, C. A. (2010).New Flora of the British Isles (Third ed.). Cambridge, UK: Cambridge University Press.ISBN9780521707725.
^Cutler, Tony (2020).The world encyclopedia of trees: a reference and identification guide to 1300 of the world's most significant trees. London?: Lorenz Books.ISBN978-0754834755.
^The complete encyclopedia of trees of the world : the ultimate reference and identification guide to more than 1300 of the most spectacular, best-loved and unusual trees around the globe, with 3000 specially commissioned illustrations, maps and photographs. Creative Media Partners, LLC. 10 September 2021.ISBN978-1015282605.
^abPigg, K.B.; Manchester, S.R.; Wehr, W.C. (2003). "Corylus,Carpinus, andPalaeocarpinus (Betulaceae) from the Middle Eocene Klondike Mountain and Allenby Formations of Northwestern North America".International Journal of Plant Sciences.164 (5):807–822.doi:10.1086/376816.S2CID19802370.
^Forest, F.; Savolainen, V.; Chase, M. W.; Lupia, R.; Bruneau, A.; Crane, P. R. (2005). "Teasing apart molecular- versus fossil-based error estimates when dating phylogenetic trees: a case study in the birch family (Betulaceae)".Systematic Botany.30 (1):118–133.doi:10.1600/0363644053661850.S2CID86080433.
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