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|Larix decidua in autumn|
About 10–14; see text
|Larix decidua in autumn|
About 10–14; see text
Larches are conifers in the genus Larix, in the family Pinaceae. Growing from 20 to 45 m tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains further south. Larch are among the dominant plants in the immense boreal forests of Russia, Canada, and Scandinavia.
Although a conifer, the larch is a deciduous tree and loses its leaves in the autumn. The shoots are dimorphic, with growth divided into long shoots typically 10–50 centimetres long and bearing several buds, and short shoots only 1–2 mm long with only a single bud. The leaves are needle-like, 2–5 centimetres long, slender (under 1 cm wide). They are borne singly, spirally arranged on the long shoots, and in dense clusters of 20–50 needles on the short shoots. The needles turn yellow and fall in the late autumn, leaving the trees leafless through the winter.
Larch cones are erect, small, 1–9 cm long, green or purple, ripening brown 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 (1–3 cm) with short bracts, with more southerly species tending to have longer cones (3–9 cm), often with exserted bracts, with the longest cones and bracts produced by the southernmost species, in the Himalayas.
There are 10–15 species; those marked with an asterisk (*) in the list below are not accepted as distinct species by all authorities. 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 is 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.
Most if not all of the species can be hybridised in cultivation. The best-known hybrid is the Dunkeld Larch Larix × marschlinsii (syn. L. × eurolepis, an illegitimate name), which arose more or less simultaneously in Switzerland and Scotland when L. decidua and L. kaempferi hybridised when planted together.
Male (above) and female (below right) cones of Japanese Larch emerging in spring.
European Larch foliage and cones.
European Larch male "flowers" or strobili.
Larches are prone to the fungal canker disease Lachnellula willkommii (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 south-west of Scotland. In August 2010 the disease was found in Japanese Larch trees in counties Waterford and Tipperary in Ireland.
Larch is a wood 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 panelling. The timber is resistant to rot when in contact with the ground, and is suitable for use as posts and in fencing. The hybrid Dunkeld Larch is widely grown as a timber crop in northern Europe, valued for its fast growth and disease resistance. (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).
In central Europe larch is viewed as one of the best wood materials for the building of residences. Planted on borders with birch, both tree species were used in pagan cremations.
Larches are often used in bonsai culture, where their knobby bark, small needles, fresh spring foliage, and – especially – autumn colour are appreciated. European Larch, Japanese Larch, and Tamarack Larch are the species most commonly trained as bonsai.
The larch was a recurring topic in Monty Python skits.
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