Farm Forestry New Zealand

Larch is light demanding and only grows on well-drained soils. Though it is hardy and windfirm it prefers natural shelter and slopes that shed cold air. It is a deep rooting tree, grows well in deep fertile clay soils and can productively grow at altitudes of up to 600 m. Although very frost hardy in winter larch is very susceptible to frost in spring when its new shoots flush.

Planting

Container-grown and bare-rooted stock is available from some commercial nurseries; Price per tree should range from $0.80 - $2.50 for 1-2 year-old contract-grown forestry stock (2020 prices). Japanese larch seedlings should be ordered well in advance so the nursery can secure seed, which is only available seasonally. Soil mycorrhizae from a well established stand of trees should be added to the nursery soil or media.

Plant in winter. If hard late frosts are expected, plant after these and use wetted water-absorbing gel in the planting holes to ensure the trees don’t dry out before they establish roots. Make sure that competing brush weeds are well controlled before planting.

Spacing

When growing larch for timber a suggested approach is ensure sites are free of gorse and broom and plant at 1250 stems per hectare (4m x 2 m) with high quality stock. However this might seem excessive if the plan is to thin to below 400 stems per hectare and an initial 833 stems per hectare (4m x 3m) might be as effective.

Releasing

Larch is light-demanding and hates weed competition, especially overtopping brush weeds such as broom. With good weed management its early height growth is fairly vigorous, up to 1 m a year over the first 5-6 years. Release spray after planting to control weed regrowth, then check the trees annually and spray or clear weeds until the larch is 2-3 metres high, when they can generally outgrow anything but climbing plants such as blackberry (which should be cleared before planting). Avoid spraying the trees.

See Successful establishment of tree seedlings »

Grazing/Browsing

Larch foliage is highly palatable and slender trees can be pushed over by sheep and cattle. Stock should be fenced out until the trees are big enough to withstand damage, but the timing and intensity of grazing require careful consideration.

Young larch seedlings are palatable to hares and rabbits. They will slice off trees near ground level at a 45 degree angle, killing them.

As larch is palatable to possums, control this pest with poison, trapping or shooting as they can occasionally causing severe damage by ringbarking older trees high in the crown.

Pests and diseases

Larches are relatively healthy compared with many other exotic forest species in New Zealand. They are not greatly susceptible to any particular insect or fungal pathogens: if there is an attack it can sometimes be related to improper siting. Larch canker is a major disease in Europe but is not present here.

See Pests and diseases of larch »

Japanese larch prefers cool conditions and has fast juvenile growth. Being hardy and deciduous, it is favoured for its landscape value and seasonal changes of colour. It has been planted on a small scale for timber and on farms in several regions of New Zealand. As farm shelter, larch is particularly useful for east-west shelterbelts because it loses its leaves and minimises winter shading.

Suitability for steep slopes: Grown for timber larch is reasonably productive over long rotations and tolerates shallow soils found on steeper slopes, lending itself well to steepland regimes for controlling erosion. Although larch is a pioneer species with a high wilding potential, spread is easily controlled by grazing animals and it is not likely to be an issue in North Island hill country with good rainfall. Japanese larch and hybrid larch are both well suited to North Island hill country. Hybrid larch (European X Japanese) is faster growing than either pure species. Being sterile it does not pose a wilding risk.

While larch may be grown for timber, Douglas fir produces similar wood, is more site tolerant and grows slightly faster. A good summary is given in the report: Trees for steep slopes - larch.

Pruning

Larch has good form with few malformations or double leaders. Larch will grow tall, but lightly branched and at less than 500 stems per hectare will produce sawlogs with good diameters. To develop quality clearwood larch requires pruning.

Prune the stem in 3 to 4 lifts (depending on site productivity) to a stem diameter of 12 cm, and to at least 6 metres height. Prune annually from approximately age 6. Epicormic shoots may need removing.

Thinning

Larch has a narrow conical form with small abundant branches that are light demanding. Grown for timber larch should be thinned regularly to ensure the stand does not become overcrowded leading to death of lower branches and formation of bark-encased knots. Reduce the stocking to the best 400 stems per hectare for a 40 year rotation. Alternatively, production thin at 30 years and grow the best 200 stems on for a 50-60 year rotation.

When to harvest

A practical rotation length of 40 years or more is recommended.

Grown for erosion control on steep faces as a permanent forest, larch could be harvested on a target diameter basis as soon as it reaches around 45 cm diameter at breast height, which could be between 30 and 50 years depending on site conditions.

Larch timber is similar in properties and appearance to Douglas fir, with excellent toughness and stiffness but only moderate durability. The wood air dries readily but care is required in kiln drying. Even small logs have a high proportion of heartwood, which is resistant to insect or borer attack but not suitable for ground contact. The heartwood is resistant to water based (CCA) preservatives.

Larch has been approved as a framing timber since 1975. It is popular for roof tile battens because of its small tight knots and has been used for floors, scaffold planks, beams, columns, and other exacting uses where toughness is required. It may be used for weatherboards, and is flexible in thin strips for yacht building. It is an attractive decorative timber for panelling, and may be sand-blasted to accentuate the contours of its surface grain. The roundwood is popular for rustic work.

Markets and demand

There is small market for larch timber in New Zealand. A handful of mills around the country have developed a small marketplace. Export log markets are available.

Growth and yield for larch plantations have not been quantified. However 30 year old larch are typically 16-20 m high with 25-30 cm diameters at breast height, while 60-80 year old trees reach 35 m height and 40-50 cm in diameter. On good sites the growth rate appears to exceed that of Douglas fir.

Practical hints for measuring trees offers some advice on monitoring growth.

As larch is an exotic softwood, tables A2.2 and A2.4 apply, suggesting that over its first 30 years it stores carbon roughly half as fast as radiata pine.

Timber return on investment

There are no studies of the economics of Japanese larch, but based on productivity and export log prices it would likely be slightly less than Douglas fir.

• Larch - Information resources