On 2005-04-24, Alan Gould wrote:
In article , Ceri Davies
writes
"Long enough" being about the same as this here piece of string?

The length of time for which the soil is deprived of light will affect
the length of time for which it will remain weed free after removing the
light barrier. A very rough rule of thumb is that the ground treated
will remain weed free for about the same time the barrier is in place.

That is because although the barrier will quickly kill off any top
growth, and some less vigorous root structures, hardier weed roots can
remain alive in those conditions for quite a long time. When exposed to
normal conditions of light, air and water, those still living roots will
reactivate and develop again into plants. For all weed growth to be
eliminated by this method, the barrier needs to be in place for 18-24
months. Even then the area of soil treated will begin to accumulate
weeds by the many other methods in which they are naturally propagated,
i.e. not by the re-growth of those which had already existed there.

Good explanation; thanks Alan.

Ceri
--
Only two things are infinite, the universe and human stupidity, and I'm
not sure about the former. -- Einstein (attrib.)