On 29/04/18 12:14, Nick Maclaren wrote:
In article ,
Jeff Layman wrote:
On 29/04/18 09:31, David wrote:
On 29/04/2018 06:37, Chris Hogg wrote:
On Sat, 28 Apr 2018 22:52:20 +0100, Tim Watts
wrote:

If you do the "cover some ground with a blackout sheet" thing, how long
should you leave it at this time of year to kill everything?

I have an uncared for raised bed and the kids would like to own it for
some flowers and stuff. Rather than nuke it with glyphosate, I have some
scrap DPM sheet (heavy black plastic).

I just wondered how long?

Depends on the type of weed and time of year. In spring/summer,
perhaps only a couple of months, but at least twice as long in winter.
Deep-rooted weeds may also survive a lot longer than shallow rooted
ones. DPM should be fine, but thin stuff like black bin-liner might be
just let enough light through not to be effective. Weight the plastic
down with stones, bricks or just earth to stop it blowing around.

Glyphosate is quicker.

If you have intractable perennial weeds, you would need to cover it
for at least a growing season. And, even using glyphosate half strength
(which works better), you may have to do that for several years on those.

Or just dig it over, no chemicals and ready to use once done.

And if he has ground elder, horsetail, bindweed, creeping buttercup, etc
, etc is that still the advice you would give?

Clearly.

? Did you intend to write"Clearly, not"?!

But it does work for the shallow-rooted ones, like ground
elder, couch grass and probably creeping buttercup. If you can dig
it over to a depth of at least a foot, leave it for a month or so for
the surviving bits to come through, and repeat, you will have almost
eliminated them. But it's damn hard work, and you have to remove ALL
the bits of roots that you see each time.

I was taking issue with David's "... and ready to use once done." As you
note, it needs a lot more than one digging over.

Field bindweed and horsetail are almost ineradicable. If you dig the
former up to a depth of at least 6" every time you see it, you will
kill it within about 5 years. Using half strength glyphosate whenever
it greens up will also work within a few years, but full strength is
a disaster.

I used full-strength glyphosate to eliminate bindweed and it worked in
just over year. If I remember correctly, it took four or five sprayings
over several months. But today I found a piece coming up in a different
part of the garden next to a bit of rough land. :-(

--

Jeff