permaculture

[kahless@waymark.net]

>So, in his case, tilling would destroy the natural vegetation;
>decapitating at prime time is too labour intensive . . . etc. I
>think I mentioned he is presently mowing them down in the
>hopes of weakening them.

Quoting from "Common-Sense Pest Control" by Olkowski

". . . It is not until just after blossoming that surplus nutrients become
available
 for storage in the roots.  These nutrients are used to initiate new growth
the
next season."

"This suggests that if your efforts to dig out or otherwise kill mature
perennial
weeds are insufficient, an alternative strategy is to exhaust nutrient
reserves in
the roots and prevent their resupply by repeatedly destroying new top
growth as
it emerges early in the growing season.  This forces the roots to use up
stored
nutrients to develop new stems and leaves.  Eventually the nutrient supply is
exhausted completely and new growth does not appear.  Without leaves to
photosynthesize and supply new food, the roots die."

"To achieve the greatest effect, top growth should be removed before the weed
begins to translocate (move) food reserves down to the root zone for
storage for
the following season.  This translocation occurs just before or during the
early
stages of flowering.  Removal of top growth at this point also takes
advantage of
the fact that root nutrient reserves are already low, and thus the plant is
less
able to generate new leaves and stems.  Resupply of nutrients also can be
reduced
by limiting the access of plant leaves to sunlight, water or minerals."

and later:

"If you persist, even the toughest-to-control perennial weeds such as Canadian
Thistle will succumb.  Candian botanist Dr. R.J. Moore, writing in the
"Canadian
Journal of Plant Science", describes a study conducted on a large field in
Kansas
that was completely covered with this thistle.  A series of systematic mowings
with the blade as low as possible, one month apart and four times a season,
exhausted root nutrients and resulted in the removal of practically all the
thistle
in two or three seasons."
===