Root pruning

[AA Teccie (Paul)]

Interesting case last week.

 

One of our 'rogue' roots has been implicated in the structural damage to a 100 year old listed wall.

 

The root has been hand excavated by the contractor to prove its presence and we agreed to the severing of said root at the point of the boundary line between the two properties (which oddly enough is not the wall) .

 

we may agree a root barrier depending on the results of further root investigation.

 

 

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Hi David,

 

Perhaps not so applicable under these particular circumstances given both the age of the wall and the type of structure etc. but in many previous instances involving direct root damage to boundary walls we have requested that, because they have to be rebuilt anyway, they incorporate an engineering solution to allow root retention, e.g. brick piers n concrete lintel.

 

Not all cases lent themselves, and this one wouldn't, but under the right circumstances, and for the right tree, don't forget to consider alternatives...often outside the 'box' normal.

 

Cheers, n hope yer well..

Paul

[David Humphries]

Hi Paul,

good thanks, hope things are well for your good self also

 

A fine point and one I don't have an awful lot of experience in, although we did find a decent (debatable) solution to a root/buttress issue on another listed wall built circa (1766)a few years ago.

 

I believe the idea of a root barrier is being discussed in relation to the ash from earlier in the thread.

 

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[Gary Prentice]

You get all the interesting jobs, David:sneaky2:

[David Humphries]

Not all of them

 

 

 

 

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[treeseer]

Off topic but is the trunk of that beech pushing on the roof? I typically advise to prune the building, but that might not be accepted here.

[Amelanchier]

There's very little in BS3998:2010 on root prunning other than cutting to as small a diameter as possible and leaving clean cut surfaces.

 

I've actually done a little bit of original research work on root severance response since I started this thread (eight years gone in the blink of an eye David!) and I think best practice has this a bit wrong.

 

We normally specify small clean cuts in the canopy to minimise the available colonisation surface and to ensure our nice pruning work isn't overrun by epi within a couple of years. And when we do want a vigorous growth response we might work in a bit of natural fracture veteranisation (acknowledging that we probably increase the decay risk). All this is, of course, is just controlling the amount of exposed cambium. More exposed cambium typically means more meristem differentiation and more regrowth. Less normally equals less, and in that respect roots are no different from branches.

 

But as Guy notes above, roots compartmentalise far better than branches or stems so unless we are right up to the structural stuff we shouldn't really worry about facilitating decay (with the caveat that common sense still applies - we should probably leave the last Cat A trees in a group that was decimated by Armillaria alone, mentioning no names Devs & LPAs ). So the pruning spec should come down to what growth response we want. As it stands, the guidance doesn't let us do that.

 

Personally, I find few occasions where I don't want cut roots to re-grow as well as possible. After all, we've just sanctioned the loss of a technically unknowable volume of roots so letting the tree regenerate as much as possible is likely to be pretty important. With that in mind and provided that the goal of the severance is achieved and its re-occurrence abated, do I really want a nice small clean cut with minimal cambial exposure?

 

Assuming David's duff Ash were of a bit better quality, I'd be tempted to say that we should look to underpin the wall with a nice big block of concrete or similar (there's a proper root barrier for you) and smash the root out with a digger...

 

How's that for out of the box Paul

[David Humphries]

Was hoping the bait was sufficient enough to lure you up out of the deep dark blue depths of the Arb Ocean

 

It was previous comments you've made regarding root wounding that got me to think about resurrecting this 'old' thread.

 

No point in starting new ones when there's a relevant platform already out there

 

Thanks for jumping back on sir

 

 

 

 

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[treeseer]

"And when we do want a vigorous growth response we might work in a bit of natural fracture veteranisation (acknowledging that we probably increase the decay risk). All this is, of course, is just controlling the amount of exposed cambium. More exposed cambium typically means more meristem differentiation and more regrowth"

 

'Typically' seems to imply some kind of experience. I've looked hard and asked everyone I can think of, but seen no indication anywhere that exposed cambium = more vigorous regrowth. Did your research turn up any support for this hypothesis?

 

The vigorous regrowth that we want comes from dormant buds at interior nodes.

[Amelanchier]

'Typically' seems to imply some kind of experience. I've looked hard and asked everyone I can think of, but seen no indication anywhere that exposed cambium = more vigorous regrowth. Did your research turn up any support for this hypothesis?

 

The vigorous regrowth that we want comes from dormant buds at interior nodes.

 

You see that's the problem with simplification. One size does not fit all.

 

We also get adventitious bud formation in callus tissue. Especially in species with low populations of dormant or latent buds e.g., Fagus sylvatica.

 

Tree Roots In The Built Environment: Research For Amenity Trees 8 by Roberts et al presented the attached model for root regrowth post severance based on their analysis of the work of Gary Watson. They maintain that the primary source of new root buds is callus tissue which differentiates from the exposed cambium post injury.

[treeseer]

Sorry we bounced from roots to branches there. Back to roots: Yes those are lovely pictures that may represent regrowth after the shock of transplanting with a tree spade.

 

I've seen cuts from other pruning that had no regrowth at the wound sites, but these were made to laterals. They did have good closure.

 

Watson also reports that new growth from inner, proximal growth points was rapid. But that's not so easy to relate in imagery.

Still waiting for support for the speculation that more exposed cambium = more vigorous regrowth. Did your research turn up any support for this hypothesis?