The history of larch plantings for timber outside their natural range is a long one. This has lead to the realisation that closely related larch species, when planted close together, can hybridise. Hybrids have also been produced and planted deliberately, often being faster-growing than their parent species. This characteristic is known as heterosis, or hybrid-vigour. The best-known hybrid world-wide is that between the Japanese and European larches (Larix x marschlinsii), known as “Henry’s larch” in Finnish, but Dunkeld or simply Hybrid larch in English.
The Siberian larch is native to the areas on both sides of the Ural Mountains. It is spreading west and the nearest natural forests can be found on the eastern shore of Lake Onega (Ääninen in Finnish) in Russia. The species grew in Finland before the last Ice Age and thrives now throughout the country. The straight trunk and fine branches make it an ideal forest tree. The crown is narrowly conical. The young branches are stiffer than those of other larches and seldom droop. In autumn it is the first larch to change colour.
Olga Bay larch is native to North Korea and neighbouring areas where the climate is similar to Finland’s. Fast-growing, hardy, and beautiful, it grows well in southern and central Finland. Unfortunately, it has so far been planted almost solely in scientific collections. Significant characteristics in identifying the species are the slightly upward-growing branches, very short needles and the cones, which are shiny red before ripening.
Western larch is native to a restricted area in the western Rockies in North America. In Finland it grows successfully only in the richest and warmest sites in the south of the country.
It is most easily distinguished from other larches by its cones, where the seed bracts extend beyond the cone scales. It is narrower in habit than the other larches and large-growing, achieving heights of 40-50m.
American larch, or tamarack, is easily identified, even from a distance, by its crown of slender twisting branches. The tree is slender and small in comparison with other larches. It grows quite rapidly when young but remains shorter and more slender than Siberian larch (Larix sibirica), for example. The tamarack’s needles are blue-green, turning to yellow in autumn, brightening the landscape before they fall. The cones are small, just a little larger than a pea.
The Japanese larch, from the mountains of Honshu Island, is hardy in Finland to zone III, i.e. quite far inland. The species has grown at Mustila since about 1910 and has suffered little or no damage even in the coldest winters of last century. However, when young the seedlings are rather tender to autumn frosts due to their maritime origin. Autumn frost can also damage the flower buds.
The natural range of the Kurile larch in eastern Asia includes the Kurile Islands, Sakhalin Island and, according to some interpretations, the Kamchatka Peninsula. The species can be grown at least to central Finland. It is easy to recognise from its long sweeping branches which produce a special feeling in the woods. The brown needles remain on the tree until late autumn, till the snows come.
Dahurian larch is native to the coldest parts of east Siberia, where it forms the world’s northernmost forests on the Taymyr Peninsula, on the shores of the Arctic Ocean. This species even grows in the coldest area in the northern hemisphere, in the Verkhoyansk mountains, where temperatures down to -70C have been recorded. Despite this, it struggles on through dry summers taking advantage of the moisture released by the surface melting of the permafrost. It is assumed to be hardy throughout Finland.
The Polish larch is a form of the European larch (L. decidua) found on the highlands of central Poland. Some botanists consider it an intermediate relict form between the European and the Siberian larches, based on cone shape.
The European larch is native to the mountains of central Europe, particularly the Alps. It grows well in southern and central Finland and is common in the country’s oldest larch plantations. It has also been much used in landscaping. The trunk of this species is not, on average, of the same high quality as the Siberian larch (L. sibirica), which limits its use by the timber industry.