Farm Ireland

Wednesday 21 November 2018

Thinning to fatten profits


First thinning sets the forest up nicely for the coming years
First thinning sets the forest up nicely for the coming years
Steven Meyen

Steven Meyen

I find it very satisfying to see a farmer's forest thinned for the first time. Rather than trees going into the ground, it is good to see timber coming out of a forest - putting money in the farmer's pocket.

A first thinning will also set the forest up very nicely for the coming years: a good quality road into the forest has been created; by removing trees, more space has been provided for the remaining trees; and, above all, it will give you a pretty good idea of the quality of your crop and which trees need to be removed the next time.

Gradually removing these poorer quality trees over time will provide more growing space for the remaining better quality trees.

This will create a forest of fewer trees but of greater quality, size and biodiversity value.

In a forest that has been thinned throughout its life, there should be about 500 trees per hectare at the time of clearfell, with each tree having a volume of 0.7-0.8 m3.

This is twice the size of trees in an unthinned plantation. This results in a more valuable crop as larger trees command a much higher price. Not thinning will result in a larger number of smaller sized trees, with a likely reduction in crop value.

A question that I get asked several times a week is when does thinning need to take place? Well, I prefer to thin early, especially in the west of Ireland. This will help creating a more stable forest.

However, such advice is not very popular as it makes the thinning operation commercially less attractive for both the farmer and the contractor. First thinning of sitka spruce is usually carried out when trees are between 10 and 12 metres in height. In a strong-growing crop, this can be as early as 13 to 15 years, while it can also be as late as 22 to 24 years on a less productive site.

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To figure out what is going on inside your forest, it is essential that inspection paths are cut through the forest. This allows access into and through the crop so that the suitability for thinning can be assessed.

This involves removing branches to head height between two lines of trees when the trees are about 10 years old. Parallel paths should be cut 50 to 100 metres apart depending on the size of the forest. Take appropriate safety measures if using a chainsaw. There is a short, handy video on explaining this process.

Effective and timely planning is crucial because between one thing and another, it can easily take two years or more before actual thinning will take place. In particular, building a forest road, applying for a roading grant and arranging a felling licence can be time consuming. Construction of a timber loading area or forest road should be completed one to two years in advance so the road has time to settle before harvesting commences.

Roading grants are available from the Forest Service, Department of Agriculture, Food and the Marine (DAFM). Planning permission may be required to create access from the forest on to the public road.

A general-felling licence is required to carry out thinning and usually remains valid for five years. Apply well in advance to the Forest Service (DAFM). Once the licence is in place, you decide when thinning needs to be carried out within that five year window. Application forms as well as worked-out examples are available from

And don't forget that first thinning should be all about removing inferior trees in time, allowing the valuable trees to grow to full maturity. If you want to be successful in forestry, you have to play the long game.

Steven Meyen is a Teagasc forestry advisor.

Indo Farming