UKTC Archive

RE: Green roofs and overhanging trees.

Subject: RE: Green roofs and overhanging trees.
From: Rupert Baker
Date: Oct 27 2020 20:50:20
If birds have landed on the green roof, and if the substrate resemble soil, 
then there will be worms and other soil biota to break down the leaves. 
'flat' roofs are never actually level; they generally slope at ~10 degrees or 
so; one issue with leaves is - is there a lip or upstand around the edge - 
which might trap leaves? 
Anyway, in what way does 'The Council' - presumably the LPA - have any input 
into the subsequent maintenance of a building???

Atb
Rupert

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info On Behalf Of Bill Anderson
Sent: 27 October 2020 14:31
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Re: Green roofs and overhanging trees.

The client's problem (or non-problem?) is being told to rake the leaves off 
twice a year. I thought the answer would be to stick a ladder up and then 
just blow the things off with a leaf blower, but then would that blow the 
plants themselves off? I suspect there's a potential problem in that they 
might have to get a contractor in (how many households have space to keep 
ladders these days?) and if it's twice a year it starts to look expensive for 
someone who thinks they're just doing it to satisfy a Council-generated whim.
And would a dense mulch of leaves on an area where there are no lurking worms 
to help get rid of them be quite as straightforward as a mulch in a lot of 
grass? Do green roofs have worms? And for that matter, do leaves actually 
accumulate on flat roofs? Or does the elevation mean they get blown off more 
than might be expected?
Questions, questions....
Bill.

On Tue, 27 Oct 2020 at 11:45, Tahir Sharif <tahir@xxxxxxxxxxxx.org> wrote:

Green roofs come in all sorts, some are a system with various 
membranes and u substrate over which a preplanted/seeded mat is rolled 
outn others are a loose substrate that has been seeded or planted. Our 
roof isn't near any trees but still gets a few, I can't see it would 
be a problem personally but I guess a lot depends on the owner.

Tahir

On 27/10/2020 11:33, Rupert Baker wrote:
Hi Bill,
I'd have thought that a mulch of leaves would be useful for the
continuing health of a green roof - assuming that the substrate on 
which the Sedum or WHY plants they are using is something that 
earthworms and other soil biota can survive/flourish in...
I imagine that the complaint if that is what it is relates to the
quantities of leaves, possibly suppressing the greenery? - never mind, 
the winter gales will thin the numbers down.
When I was with a local authority, one of our parks - centre-urban,
shrub-beds with trees round outside, grass in middle, lots of big 
Planes and Limes - 25-30m+ x 80-100 dbh - used to get covered in 
leaves in autumn/winter - one would get complaints from dogwalkers etc 
about untidiness and mud; and the grass would largely disappear.
Next spring, back it came.
And that was on a fairly artificial surface; like many of the parks 
it
had been a municipal waste tip, with an incinerator at one end - 'nice'
smoke drifting down the valley - (talking late 19thcentury here) 
before having a skim of soil over the glass, clinker, tins and 
carcinogens, and becoming landscaped as a park. Various anoraks 
amongst the parkies had a lovely time 'bottling' and selling or 
displaying the old bottles they excavated whilst 'digging over the shrub 
border'
So I'd suggest to the owner not to panic; as long as it has a decent
substrate, and doesn’t bake hard and dry in summer, it should be fine; 
the ones I've seen often look a bit patchy after a few years; they are 
not an install and forget option, but need regular tickling of one 
sort or another

Atb
Rupert

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info On Behalf Of Bill Anderson
Sent: 27 October 2020 10:08
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Green roofs and overhanging trees.

What ho.
Just had a query from a client along the lines of what do I know 
about
green roofs? Apparently they've been told to rake the fallen leaves 
off twice a year.
I have absolutely no knowledge of this topic so was wondering if 
anybody
else had. Especially as green roofs are becoming more common and even 
a requirement on some developments.
I think in this case there's potential for an argument about a 
street
tree, and of course it's in the heart of Sheffield's protest area, but 
it seems there might be another potential clash between trees and a 
planning policy.
I'd be interested to hear of anyone's experience.
Thanks as ever,
Bill.



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The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC forum is supported by Bosky Trees arboricultural consultancy and
Stockholm Tree Pits
https://www.stockholmtreepits.co.uk