On Wed, 25 Jul 2001 22:26:38 +0100, you wrote:
Mulch is used as a weed suppressant,for moisture retention and to "darken"
soil on developments, I think it is poor for the first, outperformed
by modern artificial treatments for the second and a fraud for the
I'm not sure that is entirely borne out in the research papers and
There's no doubting the efficacy of herbicides, but we have certainly
had reasonable results in farm woodland establishment trials with
mulch as a weed suppressant. I also seem to recall that the most
recent ISA research (2000?) showed mulches performing pretty much as
well, if not better than other soil ameliorants.
I will try and put my case as David and yourself have commented.
First in these matters there is no black and white answer, I have no
doubt that woodchips act as a mulch, suppress weeds or change the
colour of a soil to make a poorly reinstated site look more
For potting purposes I think there are now moisture retaining
additives (based on seaweed/?? polyacrimides? ) which have far better
performance than peat.
Coming from a forestry background I am used to using a chemically
screefed spot to maintain weed free conditions (and hence less
competition for moisture in the rooting zone). It is cheap,
efficacious and normally only needed in the first year of
establishment (though benefit can be seen for several years). On trial
plots at the front of Alice Holt the better growth and weed free
conditions is plain to see between mulched and spot weeded treatments.
I well remember a planting of birch standards in a line alongside the
river Wey in Perrinville. All the birch planted in the grassed areas
had died, all those in the cultivated flower bends were alive and
thriving, a classic example of the need to remove competition during
I had an experience in about 1978, when I planted an avenue of 90ish
tilia "euchlora" in Sutton Green ( they remain a constant reminder to
me of how little control one has on a plan, the intent was to remove 2
of 3 and lift or "formative prune" all trees to 6m, on the grounds
that it saves on inevitable large pruning wounds when it is done too
late, they are now mop heads on 1.5m stems and intrude on the track).
Anyway several of the trees appeared to do poorly and exhibited early
leaf fall, Richard? Strouts visited from FC Pathology and took
samples. His report suggested an infection of honey fungus had arrived
on site via the sweet chestnut stakes I had used to support the plants
(even then I was not happy about CCA).
Next, in about 1991, I was removing windblown timber from Battlestone
Hill in Wisley. The curator would not allow the use of stump gobblers
because of the risk from honey fungus using the chippings as a
substrate, despite the trees having no obvious signs of infection.
This provoked an amusing incident as the stumps were too heavy to lift
in the swamp garden and inaccessible to 360 excavator, so a "little"
bellex was used!
Similarly when I started harvesting work in about 1974 the contracts
always specified no timber with a diameter more than 2" was to be left
in the plantation, this has gone by the board since then, it was a
hygiene requirement mainly to do with invertebrate infestations but I
think fungal problems were recognised (unfortunately I lent my copy of
NDG James "Forester's Companion" to an arb student who deigned to
attend work for a short period in exchange for payment and it never
came back, this may well have a refernce to this subject).
So even prior to recent discussions I was aware of problems with
applying woodchip mulch to plantings.
Note that I am referring to material that still has recognisable
"woody characteristics" in particles, whether they were previously
preserved by low pH in their original source or recently chipped. By
definition "well composted" material will not have enough food value
to support fungi, however when this stage is reached (as in spent
mushroom compost) I do not know. I am fairly certain the stuff that
left the yard as Croypost did not count as "well composted" largely
because there was not space or time to re-windrow the heaps and aerate
If any papers on the subject are eventually posted I will refer UKTC
to them, in the meanwhile could someone summarise the case for
woodchip mulch (which it has been shown contains mycelium) only being
a substrate for saprophytic fungi?
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