As the author computes the number [of trees] to an English acre, it should take just 7,840 to an Irish acre to have the trees at three feet every way from each other – this I allow to be a great number, more than twice what I have ever known to be planted.” – Samuel Hayes on the Practical Treatise on Trees (1794).

Plant spacing and stocking rates have concerned foresters since forests and woodlands were actively managed. In the above extract, Samuel Hayes is referring to John Fortescue’s 1773 publication Some Hints on Planting by a Planter. Fortescue recommended a massive 7,840/acre or 19,400/ha.

Two decades later, Hayes thought it was more than twice what was needed, which is four times the number planted per hectare for conifers today. But is this number still to high?

Up until the 1960s, the recommended stocking for conifers was 4,300/ha at 5ft spacing, while the normal stocking for broadleaves was 5,000/ha and even higher for oak. These stocking rates were regarded as excessive and today 2,500/ha for conifers (2x2m) and 3,500/ha for most broadleaves (2x1.5m) is recommended.

How do we know that these are the correct planting densities, as there are very few experiments still in existence on tree spacing to guide our decision making. I was reminded of this recently when I was asked about stocking rates in Irish forests during a visit to Weyerhaueser forest in Oregon, USA. When I replied with the above figures they were amazed – and amused – at such high stocking rates.

Their predominantly Douglas fir forests are planted at close to 3.1x.3.1m (10ft) or 1,000/ha, with even fewer plants in many reforestation sites. Stocking rates can vary from 350-400 for Douglas fir, 150-300 for ponderosa pine, 150-400 for lodgepole pine, while some foresters and forest owners add 10-20% more trees in case of damage and failures.

When I defended Irish spacing they were unconvinced. I argued that most foresters in Ireland believe that the distance that trees grow apart can have a significant impact on their growth and form, while the development of widely spaced trees leads to large heavy branches, resulting in knotty timber. I had to admit that their mature forests originally at 3m spacing were well stocked with high quality trees, without any apparent deterioration in yield and timber quality.

Their view was: why invest heavily in tree improvement programmes to ensure good form, lighter branching and overall better quality trees and still plant large numbers incurring high costs of planting, vegetation control, fertiliser (if needed) and weevil control. Weyerhausers charge more for their improved plants but growers pay extra because their establishment costs are reduced considerably and they believe yields are higher.

Wide spacing is common not only in Oregon but also Washington State and precedes tree improvement programmes which begs the question: are our stocking rates too high? In the case of broadleaves, which have poorer apical dominance than conifers, 3,500/ha is probably a reasonable stocking level, but an evaluation of stocking levels for conifers could prove worthwhile.

It may be time to carry out spacing trials using improved Sitka spruce and Norway spruce to re-evaluate plant density. It may also be time to source seed from Oregon’s Douglas fir tree improvement programmes and trial it in Irish conditions, especially on good Douglas reforestation sites.

Even a marginal reduction in plant density would provide considerable savings in reforestation sites, especially in operations such as vegetation and weevil control, mounding and planting at a time when grant aid is no longer available.

2018 storm and beetle damage in Central Europe results in increased exports to UK and Ireland

Estimates vary on the extent of damage caused by Cyclone Friederike in Central Europe in early 2018. Most of the damage was caused in Germany, where some 17m m3 of timber was blown. There was also damage in Austria, France, Benelux and northern Italy, amounting to an estimated 10m m3. The situation has been exacerbated by last year’s drought, which has been followed by bark beetle infestation of an estimated 10m m3 of wood.

Germany has increased its harvest to salvage this material, with increased exports to the UK and Ireland. This has the potential to depress prices as most of the damaged forests comprise mainly softwood – Norway spruce and pine – although hardwoods have also suffered windblow.

There is also a risk of introducing the bark beetle, which is prevalent in Norway spruce, while the black fire beetle attacks Scots pine, which is also vulnerable to Diplodia tip blight. Imports to Irish processors and manufacturers are being monitored at the point of entry by Forest Service inspectors to prevent an introduction of both beetles. So far, sawmills and Coillte spokespersons maintain that the impact on log prices is not major. Any downward pressure on prices is due partially to increased exports by Sweden to the UK, while uncertainty over Brexit continues to have a negative impact on prices. However, German log prices have fallen significantly so this has to have some knock-on price impact on construction sawn wood.

Roadside prices for spruce logs – of similar quality to Irish timber – in the storm affected regions are around €50-€60/m3 at the moment, while in other areas up to €75//m3 is achieved. In 2016, comparable prices were €95-€100/m3.

We will publish Coillte and private log prices for standing sale early next month for the first quarter, which will provide interesting information on price trends in Ireland. We will also provide an update on Forest Service disease monitoring of sawn timber imports from Germany and Austria.