Larch

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Larches are deciduous conifers in the genus Larix, of the family Pinaceae. Growing to as much as Template:Cvt tall, they are native to the cooler regions of the Northern Hemisphere. They grow in lowland forests in the far north, and high in mountains further south. Larches are among the dominant plants in the boreal forests of Siberia and Canada, making them the most abundant genus of trees on earth. Larch wood is tough and relatively durable. The wood is used in boatbuilding, cladding, decking, garden furniture, fencing, and construction. Products extracted from larch include arabinogalactan, rosin, turpentine, and an essential oil.

Etymology

The English name larch was recorded in 1548 by the botanist William Turner. It derives from the German Template:Lang, in turn from the Middle High German Template:Lang, which is conjectured to derive from an unrecorded Old High German name for the tree, *larihha. That derives from the Latin name of the tree, Larix.<ref name="Online Etym">Template:Cite web</ref> The Latin name probably was loaned from a Gaulish language spoken in the Alps.<ref name="Online Etym"/>

Description

Habit and foliage

The tallest species, Larix occidentalis, can reach Template:Cvt. Larch tree crowns are sparse, with the major branches horizontal and in whorls; the second and third order branchlets are roughly horizontal in some species, pendulous in others. Larch shoots are dimorphic, with needle-like leaves borne singly on long shoots with several buds, and in dense clusters of 20–50 needles on short shoots with only a single bud.<ref name="Stace-2010">Template:Cite book</ref>Template:Rp Larch wood is resinous. The bark of young trees is smooth; that of older trees is thick and scaly. Larches are among the few deciduous conifers, which are usually evergreen.<ref name="IDS">Template:Cite web</ref>

Cones

The male (pollen) cones are small, on the ends of shoots that die after pollination.<ref name="IDS"/> The female (seed) cones are small, typically erect, and take 4–7 months to reach maturity after pollination.<ref name="IDS"/> The seed scales spread apart when mature, allowing the winged seeds, two per scale, to fall out.<ref name="IDS"/> The leaflike bract scales can be either long and visible (exserted) or short and hidden between the seed scales.<ref name="IDS"/>

The chromosome number is 2n = 24, similar to that of most of the other species of the family Pinaceae.

Distribution

The genus Larix is present in all the temperate-cold zones of the Northern Hemisphere, from North America to northern Siberia passing through Europe, mountainous China and Japan. The larches are important forest trees of Russia, Central Europe, the United States and Canada. They require a cool and fairly humid climate, and for this reason, they are found in the mountains of the temperate zones, while in the northernmost boreal zones, they are also found in the plains. Larch trees go further north than all, reaching in North America and Siberia the tundra and polar ice.<ref name="Tsepliaev"/> The larch species Larix gmelinii is the world's most northerly-growing tree, at 75° north in the Taymyr Peninsula.<ref name="Farjon 1999">Template:Cite journal</ref>

The larches are pioneer species not very demanding of the soil and they are very long-lived trees. They live in pure or mixed forests together with other conifers or more rarely with broad-leaved trees. In 1965, larch constituted 40.2% of the forests of the Soviet Union and had a cumulative volume of 28,450 million m³, (28.45 cubic kilometres, or 6.8 cubic miles) of solid wood; by a wide margin, the most abundant genus of trees on earth.<ref name="Tsepliaev">Template:Cite book</ref>

Evolution

External phylogeny

The genus Larix belongs to the subfamily Laricoideae, which includes the Douglas firs, genus Pseudotsuga. The genus Cathaya was included in some older studies,<ref name="Farjon">Template:Cite book</ref> but based on transcriptome analysis, is now considered closer to Pinus and Picea.<ref name="Yang">Template:Cite journal</ref><ref name="Stull">Template:Cite journal</ref> The split of Larix from Pseudotsuga occurred about 45 million years ago.<ref name="Qiu">Template:Cite journal</ref>

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Taxonomy and internal phylogeny

File:107 Larix griffithii, Chelela to Paro, Bhutan.jpg
Larix griffithii in Bhutan, a species with long bracts. This attribute had been thought to define a group within the genus.<ref name="Semerikov-1999"/>

The genus Larix was described by the English botanist Philip Miller in 1754.<ref name="ACS">Template:Cite web</ref><ref>Template:Cite book</ref> In the 20th century, cone bract length was used to divide the larches into two sections (sect. Larix with short bracts, and sect. Multiserialis with long bracts), but genetic evidence does not support this division, indicating instead that the cone and bract size are merely adaptations to climatic conditions.<ref name="Germand-1999">Template:Cite journal</ref><ref name ="Stull"/><ref>Template:Cite web</ref>

Late 20th century and early 21st century genetic studies proposed three groups within the genus, with a primary division into North American and Eurasian species, and a secondary division of the Eurasian into northern short-bracted species and southern long-bracted species;<ref name="Semerikov-1999">Template:Cite journal</ref><ref name="Wei-2003">Template:Cite journal</ref><ref name="Wei-2004">Template:Cite journal</ref><ref name="Gros-Louis-2005">Template:Cite journal</ref> there was dispute over the position of Larix sibirica, a short-bracted species which is placed in the short-bracted group by some of the studies and the long-bracted group by others.<ref name="Qiu"/> Ten species and one natural hybrid of larch are accepted by Plants of the World Online (POWO),<ref name=POWO>Template:Cite web</ref> following the conservative treatment in Farjon (2010);<ref name="Farjon"/> several others are accepted by the Flora of China.<ref name="FoC">Template:Cite web</ref>

However, a 2025 study by Qiu and colleagues cast doubt on the species circumscriptions accepted by Farjon and the POWO;<ref name="Qiu"/> it showed that Larix himalaica is close to L. griffithii as geographic parsimony would predict (and not to L. potaninii as Farjon believed), and that L. speciosa is distinct and should be treated as a separate species. Conversely, they found that L. mastersiana was embedded within L. potaninii and may be best synonymised with it. Their results showed that the division between Old World and New World species as suggested by earlier studies is not correct, but rather, the primary divide is between the high-latitude circumboreal species, and the low latitude Sino-Himalayan species group, as shown in the cladogram.<ref name="Qiu"/>Template:-

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Hybrids

File:Larix x marschlinsii16.jpg
Larix × marschlinsii, the Dunkeld larch, a commercially important hybrid

Most larches can be hybridised in cultivation;<ref name=Vidaković>Template:Cite book</ref> these hybrids are not discussed by POWO as they are not of natural occurrence. Larix × marschlinsii Template:Small (syn. L. × eurolepis), the Dunkeld larch, a hybrid of L. decidua × L. kaempferi, is by far the best known: it is of major importance in forestry in northern Europe. It arose more or less simultaneously in Switzerland and Scotland in 1901–1904.<ref name="Candolle">Template:Cite journal</ref> Other named hybrids include Larix × pendula Template:Small (L. decidua × L. laricina),<ref name="Mitchell">Template:Cite web</ref> and Larix × eurokurilensis Template:Small (L. decidua × L. gmelinii).<ref name=Vidaković/>

Ecology

Species interactions

Larches are associated with some mycorrhizal fungal species, including species which primarily or only associate with larch. One of the most prominent of these is the larch bolete Suillus grevillei.<ref>Template:Cite journal</ref> Larch is used as a food plant by the larvae of moths such as the larch pug, Eupithecia lariciata.<ref>Template:Cite web</ref> The large larch bark beetle, Ips cembrae, can be harmful to already-weakened larch trees, but is in general a less serious threat than a related species, the spruce bark beetle Ips typographus, is to spruces.<ref>Template:Cite web</ref>

Diseases

Larches are prone to the fungal canker disease Lachnellula spp. (larch canker); this is a problem when late spring frosts cause minor injuries to the tree, allowing entry to the fungal spores. In Canada, this disease was first detected in 1980; it kills Larix laricina of any age.<ref>European larch canker Natural Resources Canada, accessed 23 April 2021</ref> Larches are vulnerable to Phytophthora ramorum. In 2013 the disease appeared in the Afan Forest Park in south Wales.<ref>Template:Cite news</ref> Laricifomes officinalis is another mushroom found in Europe, North America and northern Asia that causes internal wood rot. It is almost exclusive to the genus Larix. Other diseases are caused by mushrooms, fungal rusts, and bacteria.<ref>Template:Cite journal</ref>

Uses

Larch timber has many uses, including boatbuilding, exterior cladding, and interior panelling. Outdoor uses include fencing, gates, decking, garden furniture, and playground equipment. Since the heartwood is strong, durable, and available in large sizes, it is used for structures such as agricultural buildings. The Savill Building in Windsor Great Park has a timber roof shell made of many relatively thin laths, interlocking to provide strength. The wood is used, too, as fuel in industrial biomass energy plants. The bark used as a mulch in horticulture. Arabinogalactan, used in animal feed, cosmetics, and medicines, is extracted from heartwood. Larch trees can be tapped for liquid to be distilled into Venice turpentine. The tree yields rosin for violin bows and an essential oil used in aromatherapy.<ref name="FR Properties and Uses">Template:Cite book</ref> European Standard EN 350-2 lists larch as slightly to moderately durable.<ref>European Standard EN 350-2 (1994); Durability of Wood and Wood-based Products – Natural Durability of Solid Wood: Guide to natural durability and treatability of selected wood species of importance in Europe</ref> Dunkeld larch is widely grown as its timber is durable and strong, and the tree tolerates poor weather better than non-hybrid larches.<ref>Template:Cite web</ref>

In culture

The Roman architect Vitruvius conjectured in his De architectura that the Latin name for timber from the tree, Template:Lang, came from the town of Larignum, where Julius Caesar, besieging the town, supposedly discovered the larch.<ref>Template:Cite journal</ref> More recently, the Monty Python comedy troupe filmed a sketch with three schoolboys shown slides of the larch and asked which trees they were able to identify.<ref>Template:Cite web</ref>

References

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Further reading

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