bindweed killer

I received a rather snarky off-list note from a member of this list
concerning my posting about bindweed and soil. While the contents of that
note and personal attacks are of no concern to the list, her lack of
understanding and questions about basic soil microbial processes made me
aware that there were probably others who didn't understand the basics of
what I was talking about when I wrote about soil and bindweed.

I think it relevant to a list on perennials because it speaks to a whole
manner of gardening.  Soil is at the bottom (excuse the pun):-) of the
entire gardening experience. Get the soil right and you can grow darn near
anything. Screw it up and you'll have the worst gardening nightmare you can
imagine. Growing perennials depends on creating good soil. Or, getting rid
of noxious weeds.


So, with apologies to those who got it, here's version three - last and
final try.

Let me make it quite clear. Most of this data (as was credited in the last
post) is from the book "Weed Control Without Poisons" by Charles Walters.
Those of you who only wish to hear of personal experiences should stop 
reading now.;-)  I confess because I have a fertile, sand-silt soil base
(along with a good smattering of Eastern Ontario rock) I do not have a
bindweed problem. The odd one that pops up is easily pulled out. Why this
is true is the subject of the following note.

In my original posting I wrote:

"Bindweed (Convolvulus sepium) is most often found on soils that have
improper decay properties. In other words, organic matter can not decay
properly for any number of reasons."

Why can't organic matter decay? The question is rather, "what promotes
organic matter decay?"  Organic matter decays when the acidity pH,
temperature, moisture, oxygen, carbon-nitrogen ratio are in the correct
range and the appropriate soil micro-organisms are present. If any of these
major conditions are missing or off-target, then organic matter decay is
inhibited or stopped.

Let us look then at compacted soil.  Compaction smashes the soil particles
together and reduces the air spaces between them. Reduced spaces equal
reduced oxygen levels. With a reduced level of oxygen, organic matter can
not decay at optimum levels.  

Let us say that this soil is also over-watered. The spaces that used to
contain oxygen, now contain water.

Decomposition that used to use oxygen (Aerobic - in the presence of oxygen)
now turns to rotting or (Anaerobic- without the presence of oxygen)
anerobic composition.  One of the products of anaerobic decomposition is
alcohol and other preservative esters. In anaerobic decomposition, the
alcohol actually pickles the organic matter and prevents or slows down
decomposition.

Clay soils with their small air spaces due to small particle size have
similar problems as a matter of course.  This is one reason why gardeners
should never cultivate clay soils too early in the spring - you ruin
whatever air spaces are left in the soil and create concrete.

If the pH is off, then instead of primarily a bacterial decomposition,
you'll get a fungi decomposition. Different micro-organisms are supported
by different acidity levels. You have to adjust the soil pH to support
appropriate micro-organisms.

If the carbon:nitrogen ratio is not 30:1, then decomposition will not take
place. You need the nitrogen to break down the organic matter carbon. If
excess Nitrogen is found in the soil, you'll stop the entire process until
the N disappears.  Excess N will also kill many micro-organisms which
further shuts down the decomposition process.

Now filling any of these negative conditions means that organic matter will
not decay properly.  As you can see, if we simply add more organic matter
to a pile that is not decomposing, the situation will not improve. I'm sure
many of you have added material to a non-functioning compost pile and
wondered why it wasn't working. 

Something was out of balance in the compost and something is out of balance
with the soil. Adding more of the same without changing the basic
conditions will not correct a problem.

According to Walters, Field bindweed likes these negative conditions.

So, if you accept the proposition that plants are indicators of soil
conditions (and I do) then there is something fundamentally out of balance
with a soil that will support massive quantities of field bindweed. My soil
is fertile and quite well aerated so I don't have a bindweed problem. (Talk
to me about lamb's quarters and pigweed though):-) 

If you have bindweed, you'll have to decide whether you have any of these
problems and correct them. That is your decision and gardening fun.:-)

I also wrote from Walters:
"Bindweed also flourishes in soils with low humus counts (possibly related
to improper decay properties) such as sand and heavy clay soils.  Low
measurements of calcium (hence the gypsum), phosphorus, potassium and pH
also promote its growth."

So, we find bindweed in sandy and heavy clay soils (both of which have
problems with decomposition)  Low calcium and other components has been
implicated in this plant's success.

Again, if you have bindweed, you'll have to be the judge of whether any of
this material is of use to you. I make no judgement about the ability of
any gardener with any weed (Jeez, if you've seen my garden, you'll know
that weeds and I are on a first name basis):-) and you'll have to judge
whether Walters is of any use to you.

Let me repeat. Get the soil right and you can grow darn near anything.

Doug
who is going back to writing his next book 
and playing in his solar greenhouse

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