Fir - Grand fir, Abies grandis
Grand fir is a large, temperate conifer native to the Pacific Northwest of North America, where it is an important timber tree. In New Zealand it was planted experimentally from 1875 and large, handsome specimens are found around the country. Grand fir prefers deep soils with adequate soil moisture and cooler climates, tolerating wind and occasional snow but preferring altitudes of less than 500 metres and rainfall of more than 1000 mm. The closely related fir Abies concolor tolerates very cold and exposed sites. On good sites grand fir will grow for more than 400 years, reaching 70 metres height and up to 2 m in diameter.
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;
TemperatureModerate; Cold; Very cold;
WindStrong wind; Moderate wind;
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). Grand fir 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.
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.
Grand fir prefers reasonable soil depth and evenly distributed rainfall. If you are planting in a low rainfall area use wetted water-absorbing gel in the planting holes to ensure they don’t dry out before they establish roots. Grand fir will grow well in most soils, but does not tolerate poor soil drainage. Young trees are shade tolerant, but need good weed control during establishment.
Plant grand fir at 3 m x 2 m spacings to give 1667 stems per hectare. The natural form of this species is narrow conical and it will tolerate high initial stockings.
- Prevent weeds from competing with the Grand fir seedlings for at least two years after planting.
- Protect seedlings from browsing by stock and wild animals.
Grand fir is shade tolerant but establishes much faster with good weed control. Release spray after planting once weeds begin to regrow, then check the trees annually and release spray weeds until the trees are 2 metres high. Regular spray releasing is recommended for the first two years to achieve good growth rates.
All stock should be fenced out as the tree has a thin bark when young. Deer can cause severe damage to grand fir stands.
Young grand fir seedlings are palatable to hares and rabbits. They will slice off trees near ground level at a 45 degree angle, killing them.
Young grand fir may be palatable to possums which should be controlled with poison, trapping or shooting.
Pests and diseases
If grand fir has wet feet it can be susceptible to root-rot. However, in New Zealand it is generally healthy and rarely harmed by insects, disease or frost. Severe drought conditions have been reported to cause a cracking of the bark.
Grand fir is a handsome evergreen conifer with a symmetrical, narrow-conical form. It is long-lived and healthy in New Zealand and volume production can be very high.
Suitability for steep slopes: Grown for timber grand fir is very productive over long rotations, lending itself well to steepland regimes for controlling erosion. The species is not implicated in wilding spread and being shade tolerant will regenerate in light wells, making it very suitable for continuous cover forestry (i.e. where individual trees are harvested on reaching a particular size rather than a particular age). When grown for timber the target is to achieve large pruned butt logs and upper unpruned logs with green or moribund branches less than 50 mm diameter. Because of its narrow conical form and shade tolerance this species is one of the easiest to grow for timber production.
Grand fir has good form with few malformations or double leaders. Grand fir will grow tall, but lightly branched and at less than 500 stems per hectare will produce sawlogs with good diameters. To develop quality clearwood grand fir 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 Grand fir 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.
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.
Grand fir has a narrow conical form with small abundant branches that are shade-tolerant. It can be grown in regimes with longer rotations and higher stocking rates than radiata pine, but of course there is a trade-off between total standing volume per ha and tree diameter. Grand fir grows faster in full sun conditions and after 20 to 30 years makes its most rapid growth. This suggests that it should be thinned for a longer rotation of more than 40 years, and one practice is to thin to the best 500 stems/ha at about age 17, when the trees are around 14 m high.
When to harvest
When grown over longer rotations grand fir will be as productive as radiata pine. A practical rotation length of 40 years or more is recommended.
Grown for erosion control on steep faces as a permanent forest, grand fir could be harvested as soon as it reaches 45 cm diameter at breast height, which could be between 30 and 50 years depending on site conditions.
Grand fir is a very versatile softwood and like radiata pine can be used for a range of applications from paper-making through to construction.
The wood is non-resinous and non-durable. Although susceptible to decay and insect damage, grand fir is easily treated with preservatives. In the U.S. preservative-treated fir timber is commonly used for structural exterior decking on account of its strength and beauty.
The timber is favoured for structural applications such as framing because of its its ability to hold and not be split by nails and screws, and its low propensity for splintering when sawn. Strength and stiffness properties are slightly below Douglas fir but likely to be on a par with radiata pine.
Heartwood is usually white, with a pale sapwood that isn’t clearly distinguished from the heartwood. Grain is straight, with a uniform medium-coarse texture and with low shrinkage. Generally easy to work with hand and machine tools, grand fir glues, stains, and finishes well.
Markets and demand
Markets have not been established in New Zealand because little grand fir timber is available in NZ. However the species is likely to be planted widely in the future and the NZFFA is taking initiatives to determine the structural properties and grade recoveries from New Zealand grown material. Export markets are also available for logs.
Grand fir can put on 60 – 100 cm in height and 1 – 1½ cm in diameter per year even when they become quite large. The trees may reach 43 m in 50 years and some have reached heights in excess of 60 metres in 100 years. A small block at Gwavas forest in Hawkes Bay had a standing volume of over 1,500 cubic metres per hectare at age 47 and a mean annual increment of 30 cubic metres. 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 grand fir 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 grand fir, but based on productivity and export log prices it would likely be similar to Douglas fir.