Larix decidua Seeds | European Larch
LATIN NAME: Larix decidua
COMMON NAME: European Larch
Plant Profile
A European larch spends the winter looking dead, and that is its whole distinction. Alone among the widespread conifers of Europe it is deciduous: the soft green needles turn a clear gold in autumn and then drop, leaving a bare, knobbly, grey-brown tree that a stranger will take for a dead spruce. In spring the bare branches break into a haze of new green.
The mechanism behind that feathery crown is the spur shoot. Larch needles are borne in two ways: singly and spirally along the extending long shoots of the current year, and in dense whorls of thirty or more on short, woody spur shoots carried on older wood. Because most of the foliage sits on spurs, the canopy is made of small radiating brushes rather than a continuous needle mat, which gives larch its soft, misty texture. In autumn the spur carrying its needles is shed as a unit.
The disease that shaped larch forestry is larch canker, caused by the fungus Lachnellula willkommii, whose small pale cups appear in rows on dead twigs and branches. The fungus infects through a wound or a dead stub, kills the cambium in a patch, and the tree responds by growing a ring of callus around the dead tissue, producing the swollen, sunken canker that eventually girdles a stem or a main branch. The Japanese larch and the Dunkeld hybrid carry more resistance than the Alpine race of the European species.
Science & Biotechnology
The species spans a broken range, and the fragments have been named. The Alpine race is the classic tree of the high valleys, the Carpathian race is the one most planted in forestry, the Polish race is a lowland outlier of great conservation interest, and the Sudeten race is another isolated population. In the Alps, larch shares the upper treeline with the Swiss stone pine; further east it descends into the montane forest of the Carpathians. It is light-demanding and frost-hardy, and it colonises avalanche tracks, burnt ground and rockfall.
Uses & Benefits
Larch resin is an old commercial article. Trunks were tapped in the Alps for larch turpentine, also sold as Venice turpentine, a pale balsam that runs freely from a cut in the wood and thickens on exposure. Distilled, it yields an oil dominated by alpha-pinene and beta-pinene, with smaller amounts of limonene, and the residue is a resin used in varnish making.
Larch heartwood is heavy, resinous and durable in wet conditions, which is why Alpine builders roofed with larch shingles that lasted generations, and why the timber is still cut for fence posts, piling, retaining boards, boat planking and small craft. The resin that creates the durability also makes the wood slow to take paint and awkward to glue, and fresh larch boards move as they dry, so it is used where strength in wet ground matters more than appearance. Larch bark was once collected for tanning leather.
Growing from Seed
The fungus needs a wound and a mild, humid winter to get in. Frost cracks, insect damage, hail scars and careless pruning all give it a doorway, and the spores need a film of moisture on the bark for long enough to infect. That combination is common in damp valley bottoms and frost pockets, and rare on cool, airy, freely draining slopes. Practical larch growing therefore follows the site: choose ground where cold air drains away, avoid heavy wet hollows, and prune as little as possible.
Larch is the friendliest conifer for clonal biotechnology. Embryogenic cell lines can be started from immature embryos taken from developing seed, multiplied on an auxin-containing medium, matured with abscisic acid, dried down and then grown on into plantlets, and the lines can be frozen in liquid nitrogen and revived later. That means a selected hybrid genotype can be multiplied indefinitely without grafting or cuttings, and much of the basic biology of conifer embryogenesis was worked out in this genus.
Gather the cones in autumn before the scales open, dry them until the seed rattles free, then winnow and keep only the seed that sinks in water. Larch seed needs a cold moist spell, so mix it with damp sand and hold it cold through the winter, then sow thinly on the surface of a sandy seed mix in a frame and cover with three millimetres of grit; the seed requires light to start, so do not bury it. Prick the seedlings out as soon as the first true needles show above the cotyledon ring, pot them on singly, and grow them on in frames until they are twenty to thirty centimetres tall, then plant at two to three metres apart.
Our Take
If you plant a larch, plant two species and let the difference teach you. The Dahurian larch of Siberia is the toughest of the genus and will grow where the European species sulks, so Larix gmelinii is the right choice for a cold, exposed site. The Siberian larch sits between the two in hardiness and is the standard northern forestry species, and Larix sibirica is worth growing for the comparison. For a milder garden where you want the autumn gold, the golden larch of China belongs on the same list despite sitting in a different genus, so try Pseudolarix amabilis.
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