Hi!
Is there a Forester or Tree Person out there who has expert knowledge
of this subject? I have been told that the leaves from a Beech tree will poison the ground beneath so that no other species of plant will grow. Is there scientific proof of this?
Another source suggests that this is a fallacy and that the situation is caused
by the heavy leaf litter which piles up, being slow to decompose, and allowing no new growth to get through.
Having just moved into a suburban garden with several massive Fagus Sylvatica I desperately need to know.

In article ,
Dave Roberts writes:
|
| Is there a Forester or Tree Person out there who has expert knowledge
| of this subject? I have been told that the leaves from a Beech tree
| will poison the ground beneath so that no other species of plant will
| grow. Is there scientific proof of this?

Don't be so gullible! Not merely is it complete twaddle, that is
trivially checked by observation.

| Another source suggests that this is a fallacy and that the situation
| is caused by the heavy leaf litter which piles up, being slow to
| decompose, and allowing no new growth to get through.

Even that is wrong. Beech leaves are not slow to decompose.

| Having just moved into a suburban garden with several massive Fagus
| Sylvatica I desperately need to know.

The lack of growth underneath is caused by the lack of light and water
in the summer, as with most other trees. Most of the winter-growing,
deep woodland plants (bluebells and many others) will grow though. No
plant that needs to grow in summer will.


Regards,
Nick Maclaren.

Dave Roberts writes

Hi!
Is there a Forester or Tree Person out there who has expert knowledge
of this subject? I have been told that the leaves from a Beech tree
will poison the ground beneath so that no other species of plant will
grow. Is there scientific proof of this?
Another source suggests that this is a fallacy and that the situation
is caused
by the heavy leaf litter which piles up, being slow to decompose, and
allowing no new growth to get through.
Having just moved into a suburban garden with several massive Fagus
Sylvatica I desperately need to know.


With any large tree, the uptake of water by the tree and the shade
effect is enough to prevent growth underneath without recourse to poison
theories. Bluebells will grow in beech woodland. Either they are taking
advantage of higher water levels in spring coupled with more light
because the trees are not in leaf, or they have the ability to breakdown
the poison produced by the leaves.

I'm not aware of any warnings to omit beech leaves from leaf mould,
which would be necessary if they were poisonous.

I have recently been told the same 'poisoning the ground' theory about
horse chestnuts.
--
Kay

In article ,
Malcolm writes:
|
| I've not heard of beech leaves poisoning the ground. They do indeed
| build up a heavy leaf litter, which as it decomposes makes a fine source
| of mulch for the borders. More important, or so I have always
| understood, is that the canopy of a beech tree is much denser than most
| other species and so, in a beech wood, insufficient light reaches the
| ground beneath to encourage much plant growth. This should be less of a
| problem with well spaced trees.

I don't think that it is because it is denser, as such, as it is lighter
than oak, elm etc. - beech leaves are very translucent. But beeches
tend to form a solid canopy, whereas oaks, elms, etc. tend to lose whole
branches and have gaps. When a beech tree starts dropping branches, it
is not long before it dies completely - they have very little resistance
to fungal decay, once it starts - VERY unlike oaks.

I agree with you about your remark about freestanding beeches - there
are LOTS in the south, and most have even grass growing well fairly
close to the trunk (thinly, true).


Regards,
Nick Maclaren.

In article ,
K writes:
|
| I have recently been told the same 'poisoning the ground' theory about
| horse chestnuts.

Which brings to mind the good ol' Yankee expression "horse puckey".

It is true to some extent for conifer and yew needles, and to a very
limited extent for some deciduous trees (e.g. SOME walnuts), but it
is a suburban myth to believe that it is a widespread phenomenon or
stops ALL plants from growing. Some plants will grow even under
conifers, though not in a conifer plantation.


Regards,
Nick Maclaren.

On Fri, 5 May 2006 23:22:34 +0000
Dave Roberts wrote:


Hi!
Is there a Forester or Tree Person out there who has expert knowledge
of this subject? I have been told that the leaves from a Beech tree
will poison the ground beneath so that no other species of plant will
grow. Is there scientific proof of this?

Dave,

You're concerned about the allelopathy of the species Fagus. I don't
think you need worry.

Here's a paper from U of Georgia in the US that discusses the
relative allelopathies of different trees. You'll note Fagus is in
the "slight effect" section.

http://www.urbanforestrysouth.org/Re...load/file_name

If for some reason this doesn't work for you google "fagus allelopathy."

The most notorious species in this respect is Juglans nigra. I have
heard that a mature specimen can effect other plants as far as
60 feet away. For most of us, the only issue is that Juglans
regia is sometimes grafted on nigra, which could be a problem
in the garden environment.

HTH

-E
--
Emery Davis
You can reply to ecom
by removing the well known companies

The message
from (Nick Maclaren) contains these words:


In article ,
K writes:
|
| I have recently been told the same 'poisoning the ground' theory about
| horse chestnuts.

Which brings to mind the good ol' Yankee expression "horse puckey".

It is true to some extent for conifer and yew needles, and to a very
limited extent for some deciduous trees (e.g. SOME walnuts), but it
is a suburban myth to believe that it is a widespread phenomenon or
stops ALL plants from growing. Some plants will grow even under
conifers, though not in a conifer plantation.

Some trees and shrubs do manufacture and disperse (through fallen
leaves) chemicals which are toxic to other plant species and prevent
their seed germinating in the affected soil beneath. Rhododendron
ponticum, walnut and some eucalypts are in that category and I believe
horsechestnut are too. It's just one of the means that makes Rp such a
successful coloniser. Even if dense colonies of it are felled and
removed, it will be many years before the toxins fade sufficiently for
other species to seed into the bare soil left behind. (Rp seed is not
affected, of course).

Beech is not one of the trees that has that effect.

Janet

I've a huge copper beech that dominates my garden. Every 2 years, I have 25% of the canopy removed to allow light into the garden. Below the tree I have planted a suite of beds with cottage garden plants and others that attract wildlife. Plenty of compost goes into the beds in the autumn and lots of water in the growing season. The beds look wonderful and there's certainly no adverse effects from the beech tree.

The message
from (Nick Maclaren) contains these words:


In article ,
Janet Baraclough writes:
|
| Some trees and shrubs do manufacture and disperse (through fallen
| leaves) chemicals which are toxic to other plant species and prevent
| their seed germinating in the affected soil beneath. Rhododendron
| ponticum, walnut and some eucalypts are in that category and I believe
| horsechestnut are too. It's just one of the means that makes Rp such a
| successful coloniser. Even if dense colonies of it are felled and
| removed, it will be many years before the toxins fade sufficiently for
| other species to seed into the bare soil left behind. (Rp seed is not
| affected, of course).

That wasn't my experience with R. ponticum, where many plants were put
in immediately it was removed, without replacing the soil, and thrived.
Mainly camellias, other rhododendrons (azaleas) and magnolias.

I mentioned natural regeneration by seed, which rp chemically inhibits.
see P 5 of http://www.cebc.bham.ac.uk/Documents/CEBC%20SR6.pdf

Janet

In article ,
Janet Baraclough writes:
|
| That wasn't my experience with R. ponticum, where many plants were put
| in immediately it was removed, without replacing the soil, and thrived.
| Mainly camellias, other rhododendrons (azaleas) and magnolias.
|
| I mentioned natural regeneration by seed, which rp chemically inhibits.
| see P 5 of http://www.cebc.bham.ac.uk/Documents/CEBC%20SR6.pdf

Well, it doesn't say that. I makes a reference to Cross, but does not
describe details.

That implies that, like Juglans niger, it is root exudation that is the
cause. I may look at the reference if I get time, but my point is that
a lot of these effects are seriously exaggerated and often apply only
under some conditions. For example, despite frequent claims, J. niger
(the classic plant that does this) does NOT have a sterile zone under
its canopy in the UK - look at examples and see!

The reference you gave does strongly imply that the main cause of the
sterile zone is the physical blocking of light and rain, to which I can
definitely add the physical prevention of the germination of small seeds.
My guess is that is why many woodland trees go in for very large seeds
(oak, camellia, hazel etc.)


Regards,
Nick Maclaren.

"Nick Maclaren" wrote in message
...

I have Web access, but had to retype :-( Here is the relevant source
in Cross, which shows how these urban myths develop by the simplification
and extrapolation of ambiguous scientific results.

Doekson (1964) found that ground up leaves of rhododendrons caused a
reduction in the number of earthworms (Lumbricus rubellus Hoffmeister)
in peaty soil. The substance responsible was soluble in acetone, but
not in ethanol, ether or benzene. He also observed a reduction in the
numbers of L. rubellus and Allolobophora callignosa Savigny in the
soil in which rhododendrons were planted, even without the addition
of ground-up leaves. However, Lumbricus rubellus is common in the
Rhododendron humus in the Killarney woods.

Although the soils at sites 18-10 would have been greatly influenced
by Rhododendron, being almost pure stands, there is no obvious
difference with other soils. It is, however, probable that in common
with other ericaceous species, Rhododendron has a deleterious effect
on the soil, mobilising cations, directly or indirectly by the production
of phenols. Rangaswami & Verkatswarku (1966) report the presence of
polyphenols in other species of the genus, and Raudnitz (1957) has
found a humic acid in the leaves to be a water-soluble, surface-active
polyphoric ester. ...

Yeah, well. One person has found a reduction in earthworms, and another
has found little or no reduction. Several people have detected common
plant toxins (surprise, surprise!) Not a lot of evidence there.

In several other places in that paper (quoted), it referred to the
physical effects I described, and one that I did not - rhododendron
humus apparently forms a hard surface when baked in the sun.

Frankly, I don't believe that the toxin effects of either R. ponticum
or J. niger are important - whereas the physical ones of many thicket-
and canopy-forming plants with large leaves most definitely are. You
just have to look for yourself to see the latter! But it is amazing
how few scientists ever do look for themselves, as Rackham points out!


Regards,
Nick Maclaren.

I am totally with you on this one.
At my previous house we used the leafmould in volume from beneath the
Rhododendrons as a seed and potting compost without any bad effects.
It was also noticeable that the areas that had been scraped clear of debris
became host to a majority of the common garden weeds.

The message
from "Rupert \(W.Yorkshire\)" contains these words:


"Nick Maclaren" wrote in message
...

Frankly, I don't believe that the toxin effects of either R. ponticum
or J. niger are important - whereas the physical ones of many thicket-
and canopy-forming plants with large leaves most definitely are. You
just have to look for yourself to see the latter! But it is amazing
how few scientists ever do look for themselves, as Rackham points out!


I am totally with you on this one.
At my previous house we used the leafmould in volume from beneath the
Rhododendrons as a seed and potting compost without any bad effects.
It was also noticeable that the areas that had been scraped clear of debris
became host to a majority of the common garden weeds.

I think you may both be confusing the state/ results of soil under a
small local population of rhododendrons such as one might find in a
domestic garden, with the soil left after huge dense very old ones are
cleared from hilsides and woodland . It's very noticable here that when
large areas of mature woodland are cleared of their longterm 20ft tall
solid understorey of rhododendron ponticum, the only seeds that
germinate the following spring, are rhododendron ponticum. The
rhododendron leaf litter will have been swept away by winter gales
leaving visible bare soil. All around are seeding trees, but it will
takeat least two years before their seeds, or grasses or wildflowers,
start to germinate on or colonise the naked bare soil on, light-filled
woodland floor.

Janet.

In article ,
Janet Baraclough writes:
|
| I think you may both be confusing the state/ results of soil under a
| small local population of rhododendrons such as one might find in a
| domestic garden, with the soil left after huge dense very old ones are
| cleared from hilsides and woodland . It's very noticable here that when
| large areas of mature woodland are cleared of their longterm 20ft tall
| solid understorey of rhododendron ponticum, the only seeds that
| germinate the following spring, are rhododendron ponticum. The
| rhododendron leaf litter will have been swept away by winter gales
| leaving visible bare soil. All around are seeding trees, but it will
| takeat least two years before their seeds, or grasses or wildflowers,
| start to germinate on or colonise the naked bare soil on, light-filled
| woodland floor.

Well, there are two possible explanations that do not involve toxins.
One is the hard layer referred to in the Cross reference. The other
is that the pre-rhododendron weed seeds will be buried deeply under
rhododendron humus, and the new ones will not have arrived yet. The
latter case could be excluded if the effect you refer to applies to
cases when rhododendrons are cleared before midsummer, and the former
would be trivial to test by experiment.

I am not saying that the effect you claim exist can't happen, but I am
saying that 95+% of such claims are bogus and I have seen no references
that provide convincing evidence. In many cases of urban myths, there
is some truth in the myth, but it has been exaggerated beyond all reason.

In your case, you got the walnut effect wrong (it is the roots, not the
leaves, of J. niger), which is a trivial mistake, but is how myths
develop. And, as far as I know, the effect is minor and has never been
observed in other species of walnut (in particular, J. regia).

You also may well be right that there is a short-term effect in the
case of R. ponticum, though I should like to see definite evidence (memo
to self: DO ask what the Athens password is, to check the literature).
But you then claimed "it will be many years before the toxins fade
sufficiently for other species to seed into the bare soil left behind."
That is a MUCH stronger statement than the one you have just made!


Regards,
Nick Maclaren.

Many years ago oak and beech were contrasted in a natural history programme
on the BBC-it could have been radio3.
Beech has a shallow root system, and also holds on to its dead leaves well
into the winter thus denying nutrients to other trees.
Oak with a deep root system lost its leaves early in the season thus
allowing deep borrowing earth worms plenty of time to drag the leaves down.
On this account extensive beech woods do not develope a very dense
undergrowth.
Regards
David Taylor
"Emery Davis" wrote in message
...
On Fri, 5 May 2006 23:22:34 +0000
Dave Roberts wrote:


Hi!
Is there a Forester or Tree Person out there who has expert knowledge
of this subject? I have been told that the leaves from a Beech tree
will poison the ground beneath so that no other species of plant will
grow. Is there scientific proof of this?

Dave,

You're concerned about the allelopathy of the species Fagus. I don't
think you need worry.

Here's a paper from U of Georgia in the US that discusses the
relative allelopathies of different trees. You'll note Fagus is in
the "slight effect" section.

http://www.urbanforestrysouth.org/Re...load/file_name

If for some reason this doesn't work for you google "fagus allelopathy."

The most notorious species in this respect is Juglans nigra. I have
heard that a mature specimen can effect other plants as far as
60 feet away. For most of us, the only issue is that Juglans
regia is sometimes grafted on nigra, which could be a problem
in the garden environment.

HTH

-E
--
Emery Davis
You can reply to ecom
by removing the well known companies

In article ,
"david taylor" writes:
|
| Many years ago oak and beech were contrasted in a natural history programme
| on the BBC-it could have been radio3.
| Beech has a shallow root system, and also holds on to its dead leaves well
| into the winter thus denying nutrients to other trees.
| Oak with a deep root system lost its leaves early in the season thus
| allowing deep borrowing earth worms plenty of time to drag the leaves down.
| On this account extensive beech woods do not develope a very dense
| undergrowth.

Grrk. That sounds simplistic to the point of being misleading. The
delay in dropping leaves will merely delay the return of the nutrients,
not reduce it. More plausibly, a shallow root system will also deny
seedlings access to surface nutients and (more seriously) water - you
can see that effect even with herbaceous plants.

However, it is a myth, anyway. For a comparable level of cover, there
is very little difference between oak (Q. robur and pedunculata) and
beech in terms of undergrowth. Look at the trees, and woodlands
comprised of them, to see. Also, only YOUNG beech trees hold onto
their leaves beyond autumn - and hedges, which are artificially
rejuvenated. Large beeches drop their leaves later than oak, but still
leaving plenty of time for worms to drag the leaves down.


Regards,
Nick Maclaren.