Larch - Japanese larch, Larix kaempferi
Japanese larch is a sub-alpine deciduous conifer, native to central Japan and widely planted in New Zealand. It commonly reaches 20–40 m tall with a diameter of 1 metre, and grows for up to 1,000 years. It is a pioneering species that tolerates cold and thin soils and tends to spread in open country if it is not grazed. It is also an attractive ornamental used in parks and gardens.
Commercial return: Medium
AltitudeHigh altitude; Moderate altitude;
RainfallHigh rainfall; Moderately high rainfall; Moderately low rainfall;
Soil depthDeep; Moderate depth;
Soil drainageFree draining; Moderately free draining;
TemperatureCold; Very cold;
WindStrong wind; Moderate wind;
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.
Prepare grass sites by spot spraying a one metre circle for each planting site. Use glyphosate herbicide with spray dye a few days before planting as this will not leave chemical residue in the soil. Prepare spots using straight lines and accurate spacings between spots so that trees can be easily found later. Cut down woody weeds and flatten these on the ground so they decay and don't support weed growth.
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.
Take great care in the handling, transport and storage of seedlings, especially bare-rooted stock which must be kept cool and moist and planted as soon as possible after wrenching. Containerised (plug) stock should also be planted as soon as possible after receiving the plants. Make sure the root plugs are moist by soaking in a water trough.
Plant trees with a slow release fertilizer tablet underneath or put a trowel of high nitrogen fertiliser such as DAP or urea in a spade slit above the seedling.
Do not "slit and stuff" bare-rooted plants. Plant as per these instructions ».
For containerised stock, dig a hole twice the size of the plant container, leaving some soft soil at the bottom. Tease out (straighten and trim) any pot-bound roots before firming the soil around them, ensuring there are no air cavities.
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.
- Prevent weeds from competing with the Japanese larch seedlings for at least two years after planting.
- Protect seedlings from browsing by stock and wild animals.
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.
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.p>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.
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.
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.
Clearwood pruning: The aim of clearwood pruning is to minimise the defect core and produce wood free of knots. Pruning "lifts" must be regular and undertaken at a frequency that minimises branch size and diameter over stubs (DOS). Ideally, only final crop trees would be clear-pruned. The smaller more horizontal branches on lower stems of Japanese larch established within a highly-stocked stand (i.e. 1600 stems per hectare or more) will generally self-prune when they are shaded out. Larger, upward pointing branches should be removed as soon as possible as they will reduce height growth and increase defect core diameter.
Clearwood pruning guidelines are available here.
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.
Suitable pruning tools include loppers and a pruning hand-saw, a battery-operated reciprocating saw, or battery-operated loppers. Form pruning can be undertaken by using a pole pruner.
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.
Carbon sequestration rate over time, and relevant Look-up Tables
If the land is registered under the Emissions Trading Scheme and the trees are planted so as to comply, i.e. at least one hectare, with tree crown cover of more than 30 percent in each hectare and an average width of tree crown cover of at least 30 metres, then they should earn carbon credits. The relevant look-up tables for determining how quickly they store carbon and earn credits, and guides to how to use the tables, may be downloaded here.
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.