Larix Decidua0

Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to the cooler regions of the northern hemisphere, where they are found in lowland forests in the high latitudes, and high in mountains further south. Larches are among the dominant plants in the boreal forests of Siberia and Canada. Although they are conifers, larches are deciduous trees that lose their needles in the autumn.

Description and distribution

The tallest species, ''Larix occidentalis'', can reach . Larch tree crowns are sparse, with the major branches horizontal; the second and third order branchlets are also ± horizontal in some species (e.g. '' L. gmelinii'', '' L. kaempferi''), or characteristically pendulous in some other species (e.g. '' L. decidua'', '' L. griffithii''). Larch shoots are dimorphic, with leaves borne singly on long shoots typically long and bearing several buds, and in dense clusters of 20–50 needles on short shoots only long with only a single bud. The leaves (light green) are needle-like, long, slender (under wide). Larches are among the few deciduous conifers, which are usually evergreen. Other deciduous conifers include the golden larch ''Pseudolarix amabilis'', the dawn redwood ''Metasequoia glyptostroboides'', the Chinese swamp cypress '' Glyptostrobus pensilis'' and the bald cypresses in the genus ''Taxodium''.

The male (pollen) cones are greenish-yellow to orange-yellowish and fall soon after pollination. The female cones) of larches are erect, small, long, green, red, or purple, ripening brown and woody- or leathery-textured 5–8 months after pollination; in about half the species the bract scales are long and visible, and in the others, short and hidden between the seed scales. Those native to northern regions have small cones () with short bracts, with more southerly species tending to have longer cones (), often with exserted bracts, with the longest cones and bracts produced by the southernmost species, in the Himalayas. The seeds are winged. The root system is broad and deep and the bark is finely cracked and wrinkled in irregular plaques. The wood is bicoloured, with salmon-pink heartwood and yellowish-white sapwood.

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

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, 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. The larches are pioneer species not very demanding towards 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 28,450,000,000 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.

Species and taxonomy

The genus ''Larix'' belongs to the subfamily Laricoideae, which also includes the Douglas-firs, genus '' Pseudotsuga''. The genus ''Cathaya'' was also included in some older studies, but is now considered closer to ''Pinus'' and ''Picea''. The split of ''Larix'' from ''Pseudotsuga'' occurred about 45 million years ago. In the past, the cone bract length was often 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, pointing instead to a genetic divide between Old World and New World species, with the cone and bract size being merely adaptations to climatic conditions. More recent genetic studies have 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; there was some 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, but the most recent evidence strongly favours the former.

Ten species and one natural hybrid of larch are accepted by Plants of the World Online (POWO), following the conservative treatment in Farjon (2010); several others are accepted by other authors, notably Rushforth, and the ''Flora of China''.

A new study published late in 2024 cast significant doubt on the species circumscriptions accepted by Farjon and the POWO; 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 also distinct and should be treated as a separate species. Conversely, they also found that ''L. mastersiana'' was embedded within ''L. potaninii'' and may be best synonymised with it. Their results also 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.

These are subdivided on the basis of the most recent phylogenetic investigations:

Eurasian species

Northern Eurasian species with short bracts

* ''Larix decidua'' (syn. ''L. europaea'' ) – European larch. Mountains of central Europe.
* ''Larix sibirica'' – Siberian larch. Plains of western Siberia.
* '' Larix × czekanowskii'' – an accepted hybrid between ''L. gmelinii'' and ''L. sibirica''.
* '' Larix gmelinii'' (syn. ''L. dahurica'' , ''L. cajanderi'' ) – Dahurian larch. Plains of central and eastern Siberia.
* '' Larix principis-rupprechtii'' – Prince Rupprecht's larch. Mountains of northeastern China (disputed; accepted by Rushforth and many Chinese botanists; treated as a variety of ''L. gmelinii'' by POWO despite its disjunct distribution and much larger cones).
* '' Larix kaempferi'' (syn. ''L. leptolepis'' ) – Japanese larch. Mountains of central Japan.

Southern Euroasiatic species with long bracts

* '' Larix potaninii'' – Chinese larch. Mountains of southwestern China (southern Sichuan, northern Yunnan).
* ''Larix mastersiana'' – Masters' larch. Mountains of western China (northern Sichuan). Should probably be included in ''L. potaninii''.
* '' Larix griffithii'' (syn. ''L. griffithiana'') – Sikkim larch. Mountains of the eastern Himalayas, on the wet (high monsoon) southern slopes.
* '' Larix himalaica'' - Langtang larch. Mountains of the central Himalayas (disputed; accepted by Rushforth and the ''Flora of China''; treated as ''L. potaninii'' var. ''himalaica'' by Farjon and POWO despite being geographically distant from it; Qiu et al. 2024 suggest treatment as a variety of ''L. griffithii'' instead, but did not formally publish the necessary new combination).
* '' Larix kongboensis'' - Kongbo larch. Mountains of southeastern Tibet, on the dry northern side of the Himalaya in the Yarlung Tsangpo Grand Canyon area (disputed; accepted by the ''Flora of China''; treated as a synonym of ''L. griffithii'' by POWO despite its smaller cones and other distinct characters; not analysed by Qiu et al. 2024).
* '' Larix speciosa'' - Burmese larch. Mountains of southwestern China (southwestern Yunnan) and northeastern Myanmar (disputed; accepted by Rushforth, the ''Flora of China'', and Qiu et al. 2024; treated as a variety of ''L. griffithii'' by Farjon and POWO despite being geographically distant from it, and closer to ''L. potaninii'' in range and morphology).

North American species

* ''Larix laricina'' (Du Roi) K. Koch – Tamarack or American larch. Parts of Alaska and throughout Canada and the northeastern United States from the eastern Rocky Mountains to the Atlantic shore.
* '' Larix lyallii'' Parl. – Subalpine larch. Mountains of northwest United States and southwest Canada, at very high altitude.
* ''Larix occidentalis'' Nutt. – Western larch. Mountains of northwest United States and southwest Canada, at lower altitudes (Pacific Northwest).

Hybrids

Most if not all of the species can be hybridised in cultivation; these hybrids are not discussed by POWO as they are not of natural occurrence. The hybrid ''Larix'' × ''marschlinsii'' (syn. ''L.'' × ''eurolepis''), the Dunkeld larch, a spontaneous artificial hybrid ''L. decidua'' × ''L. kaempferi'' that arose more or less simultaneously in Switzerland and Scotland in 1901–1904, is by far the best known, being of major importance in forestry in northern Europe. ''Larix'' × ''pendula'' (''L. decidua'' × ''L. laricina''), and ''Larix'' × ''eurokurilensis'' (''L. decidua'' × ''L. gmelinii'') have also been named, but are rarely seen in cultivation.

''Larix'' × ''stenophylla'' is another probable hybrid still unresolved.

Ecology

Larches are associated with a number of mycorrhizal fungal species, including some species which primarily or only associate with larch. One of the most prominent of these species is the larch bolete '' Suillus grevillei''.

Larch is used as a food plant by the larvae of a number of Lepidoptera species.

Diseases

Larches are prone to the fungal canker disease '' Lachnellula'' spp. (larch canker); this is particularly a problem on sites prone to late spring frosts, which cause minor injuries to the tree allowing entry to the fungal spores. In Canada, this disease was first detected in 1980 and is particularly harmful to an indigenous species larch, the tamarack, killing both young and mature trees.
Larches are also vulnerable to ''Phytophthora ramorum''. In late 2009 the disease was first found in Japanese larch trees in the English counties of Devon, Cornwall and Somerset, and has since spread to the southwest of Scotland.
In August 2010 the disease was found in Japanese larch trees in counties Waterford and Tipperary in Ireland and in 2013 in the Afan Forest Park in south Wales.
'' Laricifomes officinalis'' is another mushroom found in Europe, North America and northern Asia that causes internal wood rot. It is almost exclusive guest of the genus ''Larix''. Other diseases are given by mushrooms, fungal rusts, bacteria and insects.

Uses

Larch wood is valued for its tough, waterproof and durable qualities. Top quality knot-free timber is in great demand for building yachts and other small boats, for exterior cladding of buildings, and interior paneling. The timber is somewhat resistant to rot when in contact with the ground, and historically was used as posts and in fencing. However, European Standard EN 350-2 lists larch as slightly to moderately durable; this would make it unsuitable for ground contact use without preservative in temperate climates, and would give it a limited life as external cladding without coatings.

The hybrid Dunkeld larch is widely grown as a timber crop in Northern Europe, valued for its fast growth and disease resistance.

Larch on oak was the traditional construction method for Scottish fishing boats in the 19th century.

Larch has also been used in herbal medicine; see Bach flower remedies and Arabinogalactan for details.

Often, in Eurasian shamanism, the " world tree" is depicted as specifically a larch tree. Planted on borders with birch, both tree species were used in pagan cremations.

Etymology

The English name ''larch'' ultimately derives from the Latin , named by Vitruvius after the ancient 'settlement of Larignum' that Vitruvius conjectured. The story of its naming was preserved by Vitruvius:

It is worth while to know how this wood was discovered. The divine Caesar, being with his army in the neighbourhood of the Alps, and having ordered the towns to furnish supplies, the inhabitants of a fortified stronghold there, called Larignum, trusting in the natural strength of their defences, refused to obey his command. So the general ordered his forces to the assault. In front of the gate of this stronghold there was a tower, made of beams of this wood laid in alternating directions at right angles to each other, like a funeral pyre, and built high, so that they could drive off an attacking party by throwing stakes and stones from the top. When it was observed that they had no other missiles than stakes, and that these could not be hurled very far from the wall on account of the weight, orders were given to approach and to throw bundles of brushwood and lighted torches at this outwork. These the soldiers soon got together.

The flames soon kindled the brushwood which lay about that wooden structure and, rising towards heaven, made everybody think that the whole pile had fallen. But when the fire had burned itself out and subsided, and the tower appeared to view entirely uninjured, Caesar in amazement gave orders that they should be surrounded with a palisade, built beyond the range of missiles. So the townspeople were frightened into surrendering, and were then asked where that wood came from which was not harmed by fire. They pointed to trees of the kind under discussion, of which there are very great numbers in that vicinity. And so, as that stronghold was called Larignum, the wood was called larch.
:—

Gallery

File:Larix griffithii, Yathang, Sikkim, India 1.jpg, '' Larix griffithii'' foliage and cone, Sikkim, India
File:Lone Larix lyallii in fall color in the Enchantments (11 October 2024).jpg, '' Larix lyallii'' in autumn near Lake Olrun in Washington State, US
File:10 31 2008 Stand of Tamarack.jpg, ''Larix laricina'' in autumn (Vermont)
File:Larix occidentalis Navaho Ridge.jpg, ''Larix occidentalis'' (Navaho Ridge, Washington state, US)
File:Flowers of Japanese larch emerging.jpg, Male (above) and female (below right) cones of '' Larix kaempferi'' emerging in spring
File:SubalpineLarch 7769.jpg, Subalpine larch male fall foliage and cone (strobilus)

References

Further reading

*
* Quote from p. 729.
* Phillips, D. H., & Burdekin, D. A. (1992). ''Diseases of Forest and Ornamental Trees''. Macmillan .

External links

''Larix'' images at the Arnold Arboretum of Harvard University Plant Image Database
* Friedman, William (Ned)
"Larch cones in spring"
''Posts from the Collection'', Arnold Arboretum of Harvard University, 2 April 2016. Accessed 26 May 2020.
* Rose, Nancy
"Not All Conifers are Evergreen"
Arnold Arboretum of Harvard University website, 6 January 2016. Accessed 26 May 2020.

"Snow Scenes, winter, larches 1977"
''Library Featured Images'', Arnold Arboretum of Harvard University website, 21 November 2019. Accessed 26 May 2020.
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Deciduous conifers
Taxa named by Philip Miller