On 21/06/2019 13:20, Chris Hogg wrote:
On Fri, 21 Jun 2019 10:17:40 +0100, Roger Mills
wrote:

I have a patio area/path consisting of a couple of inches of pea gravel
on top of some weed matting.

When I first created this 20-odd years ago, I gave the soil a liberal
dose of sodium chlorate before laying the weed matting. This kept it
weed-free for quite a few years, but the matting has now deteriorated -
allowing a lot of weeds to take root.

I have removed the gravel and the weeds, and am about to take up the
matting and renew it before covering it with new gravel. I need to be
able to neutralise the soil in order to prevent any roots or seeds left
in from growing. I don't think you can buy sodium chlorate any more.
Most of the weedkillers available seem to be of the systemic type -
which kill existing weeds but don't affect the soil. But that's not what
I want!

Any bright ideas?

The original version of 'Pathclear' was quite effective at suppressing
weed germination for quite a while, a season or perhaps longer. But it
contained simazine, and was banned by the EU about 10 years ago, IIRC.
The replacement version they claim is effective for three months, and
opinions that I've read suggest it's not nearly as good as the
original.

But I'm not convinced that annual weeds will come up through a
weed-proof membrane, but deep-rooted perennial weeds may well do.


They dont need to. The sit on top of it. Annual weeds seed themselves
like crazy

Perennial weeds you just round up or pull up

But it's inevitable that over time, however well you've sterilised the
soil under the matting, soil from airborne dust will gradually
accumulate in the gravel; airborne weeds seeds will then germinate in
that soil. Regular application of the latest version of Pathlear will
help suppress them, but it needs to be repeated regularly through the
year which is APITB.

I don't think there is a perfect solution.

Bite te bullet and weed te thing by hand three times a year and use
pathclear three times a ytear

Ot dig it all out replace it and itlats anbouta year befire wthe firs
tweeds arrive


--
Future generations will wonder in bemused amazement that the early
twenty-first centurys developed world went into hysterical panic over a
globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to
contemplate a rollback of the industrial age.

Richard Lindzen