Crown thinning large beech

[mattyboy]

I have been asked by client to crown thin a large beech to reduce wind sail and likelihood of failure. I am aiming to go through the tree one large branch at a time and take around 10-15% of weight off overall branch weight with aim of creating an evenly thinned tree. I will prioritise taking out branches that are damaged, have v shaped unions or just appear in high density with neighbouring branches trying not to take anything out larger than around 4 inches in diameter. The outside shape of the tree is to stay same of course.

 

How does this sound for a spec of a crown thin and will it give desired outcome of reducing wind sail?

 

[MattyF]

I’d would reduce / pull in the top left side a few metres and the bottom limb,pull in the right side a bit ...that part of the crown looks like it’s thinning a bit itself anyway.

As a rule for myself I would sway away from thinning mature beech because if you have to reduce it in the future you have taken a lot of the better targets out for doing, I also believe thinning creates wind tunnels and can weaken other parts of the crown and I’m all for leaving crossing branches , nature’s way of bracing.

only thinning tree you see naturally is a dying one.

That would be my spec anyway...

 

[Chris at eden]

As Matty said if you are looking to reduce sail area then a light end weight reduction would be better - if the tree needs it that is!   Thinning won't really make much difference to sail.  Doesn't have to be huge - 10% reduction of the extension will reduce loading at the base by 20%.  The tree is multi-stemmed from about 5m so the rubbing branches may be important for support so (again as Matty said) you should probably keep them.  It looks like the top might be retrenching slightly - have you checked the base for fungi? 

[Marc]

Thinning can increase transpiration and lead to further stress, with no real benefit. Keeping the density of leaves will in my opinion help to dissipate load and prevent failure.

often after wind events it’s the large old trees that survive.

 

[Dan Maynard]

Has it been reduced before? The diameter seems to reduce very suddenly on the centre stems.

If I'm right there may be a load of branches there in a bunch at the old cut, you could probably thin those out without too much harm but whether it would keep the customer satisfied I don't know.

Have they had a survey that says it needs the work or maybe had it done before?

[MattyF]

It looks wind sculpted and will, therefore, have self-optimised. No need to reduce it to an un-natural shape that pleases your eye, but isn't necessarily ideal for the tree.

 

Unless there is a defect that necessitates the work I'd thing long and hard about pruning. Beech do not respond well to pruning, reducing is worse than thinning creating larger wounds.

 

Thinning should be specified by the amount of leaf area, as a % of the total leaf area, you intend to remove, not by weight.

 

Thinning is something that should be done with secateurs. Small stuff, not big 4 inch diameter branches. Over 40 plus years I've thinned hundreds of trees, and seen many more that have been thinned, I also keep abreast of things and have never seen, or heard of any tree failing from the 'wind tunnel' effect.

 

From BS 3998

In crown thinning, an even density of foliage should be retained throughout a well-spaced and balanced branch structure which could, if required, provide an adequate framework for a possible future crown reduction.

And

Material should be removed systematically from throughout the tree rather than from the inner crown only. Cutting branches back to the main stem should generally be avoided, although structurally weak or hazardous branches should be removed if there is no alternative. 

 

As an aside, reductions shouldn't be expressed as a %. It's meaningless and it cannot be  demonstrated that what you have done is what was expected. Rather specify height and radial crown spread that is to be retained.

Good points but I would still take a minor reduction of those limbs in the left over thinning.

I have seen the wind tunnel effect a few times I’ll try and get you pictures of the remaining trees.

[mattyboy]

Thankyou all for suggestions. I do like the suggestion of reducing by a couple of metres the top left and bottom left, I think also a bit of a thin in these areas plus the top would be beneficial to the look and this is at the end of the day part of the spec to get it to 'look' more safe for customer. The right hand side of the tree gets the brunt of the SW winds so that would explain why the left hand side has bigger branches as have not had the wind on them. A similar size beech in the row blew over a month ago as it had meripilus but this one did not have any fungus in late summer(i did warn but no action was taken). Customer is just super weary and wants to do something to reduce risk on this beech.

 

I am totally up for leaving crossing branches especially when fused as they do in beech.

 

No survey done, just head gardeners plan.

 

If i thin 10% of foliage off in areas where it is dense and reduce by 2 metres top left area would this be a compromise?

Edited January 9, 2020 by mattyboy

[Chris at eden]

16 hours ago, EdwardC said:

 

 

Unless there is a defect that necessitates the work I'd think long and hard about pruning. Beech do not respond well to pruning, reducing is worse than thinning creating larger wounds.

Agreed. 

16 hours ago, EdwardC said:

 

Thinning should be specified by the amount of leaf area, as a % of the total leaf area, you intend to remove, not by weight.

Agreed again.

16 hours ago, EdwardC said:

 

As an aside, reductions shouldn't be expressed as a %. It's meaningless and it cannot be  demonstrated that what you have done is what was expected. Rather specify height and radial crown spread that is to be retained.

And again, I should have made that clear.  When I was discussing reduction as a percentage it was in relation to Frank Rinn's research on the effect of crown reduction on loading.  Not as a specification.  

[Chris at eden]

12 hours ago, mattyboy said:

Thankyou all for suggestions. I do like the suggestion of reducing by a couple of metres the top left and bottom left, I think also a bit of a thin in these areas plus the top would be beneficial to the look and this is at the end of the day part of the spec to get it to 'look' more safe for customer.

It will only really make the tree more safe if you are addressing a defect. 

12 hours ago, mattyboy said:

The right hand side of the tree gets the brunt of the SW winds so that would explain why the left hand side has bigger branches as have not had the wind on them. A similar size beech in the row blew over a month ago as it had meripilus but this one did not have any fungus in late summer(i did warn but no action was taken). Customer is just super weary and wants to do something to reduce risk on this beech.

I still think the top looks like it is retrenching from the pics, I would keep an eye out for Merip or Kretz. 

12 hours ago, mattyboy said:

 

I am totally up for leaving crossing branches especially when fused as they do in beech.

 

No survey done, just head gardeners plan.

wouldn't be a bad idea if you are unsure on what to do. 

12 hours ago, mattyboy said:

 

If i thin 10% of foliage off in areas where it is dense and reduce by 2 metres top left area would this be a compromise?

You shouldn't really be thinning and reducing at the same time as reduction is quite stressful for trees. 

[mattyboy]

Thankyou for your response Chris, much appreciate your time. No merip on it this year but will keep eye out for kretz.

 

Im leaning towards doing a 10% thin as that is just what the customer has asked but I deep down think would benefit from suitably qualified and experienced surveyor on site... which I am not!