BS5837 Category

[jacquemontii]

Please see attached photos of a mature oak.

 

Regarding BS5837 surveying, from one side the tree appears to be of high quality, a tree of visual importance as a landscape feature with an estimated life expectancy of at least 40 years, A2.

 

Then a closer inspection reveals this large wound with small cavities forming near the base of the trunk. Tapping the wound surface with a mallet reveals hollow sounding patches. Ganoderma is identified at the base, so the trunk or roots may be decaying with a white rot.

 

I know that oak as a species is very durable and the tree could hollow and remain standing for many years to come, whilst naturally shedding branches through crown retrenchment. Therefore you could still say the tree has 40+ years and in its current context in a field this tree could remain viable?

 

However, should the land use change for development, then the tree would require further consideration? Given the amount of trampling and compaction in the root zone, couldn’t this tree become a candidate for wind throw due to potential root decay? Would you therefore downgrade the tree due to impaired condition and recommend a further detailed inspection to assess the extent of decay?

 

The majority of trees I find relatively straight forward to grade, but every now and then I find the criteria difficult to apply. What do other people do in these situations? Any advice and opinions welcome.

[Arctostaphylos uva-ursi]

Sounds like you are on the right track to me.

[Paul Barton]

Great question. The categorisation method is a blunt instrument that some trees don't seem to fit! Here's my tuppence worth.

 

I would probably categorise that tree as a 'B' tree. Section 4.4.2.2 of the BS says that trees "should be assessed for their quality and benefits within the context of proposed development".

 

So, although that tree could do 40 years in its current context, I'm not sure how desirable a tree with progressive basal decay is within a new development - although of course it does depend on the plans....would the tree be in a new open space or in a back garden?!

 

I tend to reserve A category trees for particularly good examples of a species - so without the basal decay on your tree I would certainly give it an 'A'.

 

Don't forget, 'B' category trees are still a constraint that must be considered so you wouldn't be sounding the death knell for that tree by downgrading from an 'A' category.

[Andy Clark]

I would certainly echo the comments of Paul. In many cases, trying to accurately assess and apportion 5837 categories can be like trying to fit the proverbial square peg in the unfortunately non square hole.

 

I've often found myself stuck in the quandry between B1 and A2, trying to wrestle between a trees material condition and it not being the perfect specimen, and "well it may be a bit scabby, but would look absolutely beautiful if afforded due protection and made the centre piece of the development".

 

In all cases and in all my end result reports, I try and give an explanation and comentary of why and how I've reached the conclusion that I have.

 

So I would suggest trying that. Tick the box and plump for the most obvious category for data collection purposes, but then go on in the write up of your impact assessment to explain and give an account of your dilemma.

[daltontrees]

Please see attached photos of a mature oak.

 

Regarding BS5837 surveying, from one side the tree appears to be of high quality, a tree of visual importance as a landscape feature with an estimated life expectancy of at least 40 years, A2.

 

Then a closer inspection reveals this large wound with small cavities forming near the base of the trunk. Tapping the wound surface with a mallet reveals hollow sounding patches. Ganoderma is identified at the base, so the trunk or roots may be decaying with a white rot.

 

I know that oak as a species is very durable and the tree could hollow and remain standing for many years to come, whilst naturally shedding branches through crown retrenchment. Therefore you could still say the tree has 40+ years and in its current context in a field this tree could remain viable?

 

However, should the land use change for development, then the tree would require further consideration? Given the amount of trampling and compaction in the root zone, couldn’t this tree become a candidate for wind throw due to potential root decay? Would you therefore downgrade the tree due to impaired condition and recommend a further detailed inspection to assess the extent of decay?

 

The majority of trees I find relatively straight forward to grade, but every now and then I find the criteria difficult to apply. What do other people do in these situations? Any advice and opinions welcome.

 

The BS is not clear about a lot of things but it does say you can overlook minor defects. But it doesn't say you can ignore incurable active pathogens that re known to cause or contribute to premature demise of a tree. Would it be misleading to call it an A2? Almost certainly. Would it be misleading to call it a B2? Probably not. I call it the cross-examination test, and I make my decisions accordingly. Does the category feel right? Are the nearest alternative catgories any better? Would you recommend that a development with a design life of 40+ years be designed around it so that it can be enjoyed for that design life? If you were in the stand at a public inquiry, being cross-examined by some smart-ass, weasly razor-sharp QC whose job it is to destroy your self-confidence and your evidence, could you look him square in the eyes and say 'in my professional judgement, on all the available evidence, that is the most appropriate category? If you could, you've got it right.

 

Having just done a big survey where there is huge hostility to a statutory scheme and where absolutely any of the trees surveyed could become a pawn in a very high-stakes game (and a few of the trees will be), I rehearsed this test for almost every tree before hitting the 'OK' button and moving on.

 

I hope this helps you decide. I'd say it sounds like a B2. The stable hollowing of oak over long periods is well known, but in my experience more with Inonotus and Fistulina, whereas some of the Ganoderma species can destabilise quite quickly and the wind does the rest.

[jacquemontii]

Thanks to everyone for taking the time to respond to this, much appreciated. Some useful insight and its reassuring to know others also find the BS can be awkward to apply at times.

The retention categories can't always tell the whole story, so I also take the approach of including further discussion in the report to explain the pro and cons of retaining the more contentious trees.

We can make management recommendations, but ultimately the retention of the tree is the client's decision. I don't like to condemn attractive mature trees, but in the existing context and in the context of development we need to cover our liability.