Glyphosate kill delay

[Windmill]

Does anyone know how long glyphosate takes to kill various weeds? E.g. elderberry bushes, dockins, brambles, bracken, grass?

Don't want to waste money by spraying again if it's premature to do so.

[Geoff Pearson]

I put some on brambles this summer which I though hadn't worked - but 6 weeks later they keeled over, were cut down and have not re-appeared.

[Martin Brown]

In this weather you should see some yellowing of the growing points within two weeks of application and a complete kill after a month. It is a slow acting translocating weedkiller that does roots as well as top growth. If you see an immediate effect you used it too strong!

If it is wilderness that you are reclaiming the best value for money is leave it all until tinder dry. Make a firebreak around the edges and then flash burn it to see off most of the weed seeds. The black scorched earth makes it much easier to spot weed any green shoots.

[Steve Firth]

Docks and grass about a fortnight if the weather is dry, brambles about a month, elder bushes a couple of months depending on size. Bracken around six weeks to two months it seems ver resistant to glyphosate and needs several treatments possibly at monthly intervals. Also I would bump up the concentration by 25-30% for elder and bracken. ie Instead of 120-150 ml of

360g/l concentrate per five litres use 150-200 ml.

If you're buying it pre-diluted it could take ages and may not work - they dilute it to a ridiculous extent.

If the elder is large and has a significant trunk use the techniques described here previously of hashing the bark to get the glyphosate past the waterproof bark or drill holes into the trunk and top up with concentrated glyphosate.

[orion.osiris]

Seems to vary enormously. About 10 years ago, I would use Roundup against b road leaf weeds on a hot day and see them visibly start to wilt within 2hrs at most and they'd be flat out dead in a couple of days. Try using today's Roundup formulation, however, and you'll be lucky to achieve any knockdown at all. I have give up with Roundup and Weedol. I buy some cheap stuff from Wilko i n sachets that is supposed to be watered down, but I apply it neat. Still t akes about 2 weeks to kill the weeds off, though.

[The Natural Philosopher]

wait two weeks really for a tough plant.

elder and brambles are the worst. grass and docks a few days should see em yellow

[Martin Brown]

Monsanto a couple of years back were selling something they called "fast" Roundup that was more than just glyphosate. It made home users aware that something was going on within a couple of days.

The way that glyphosate works by inhibiting certain chemical pathways means that it takes a week or more before the photosynthetic byproducts build up to levels that are toxic to the plant. The growing point is usually affected first - nettles turn a nice shade of yellow as it takes effect and grass a characteristic bronze as it expires.

Sounds like a major failure to RTFM is causing to your problems.

Any generic glyphosate product will do the job apart from on a handful of Roundup Ready(TM) volunteer weeds, waxy holly and ivy and curiously buttercup which is surprisingly resistant to the stuff.

[orion.osiris]

[...]

No way. The formulation has definitely changed for the worse. Perhaps it only works effectively on Monsanto's genetically-engineered weeds. ;)

[Grimly Curmudgeon]

Woody stuff like brambles takes weeks, but when the sap draws back into the rootball at the end of the season it kills the bugger off quick-smart.

[Dave Liquorice]

The branded stuff aka Roundup, Weedol just has less of the active ingredient (glyphostae) that the generics, they may have some surficants to aid penetration though.

I'd just get the highest concentration I could, dilute if required and bruise the target plant a bit. It does take a while to act, some plants are quicker than others and some tough buggers can take more than one application. Just be patient, it does not produce an instant knockdown. Indeed by the way it works you don't want an instant knockdown.

[Rick Hughes]

Been trying to kill off Mares Tail with Glyphosphate ........ almost zero impact

[Dave Liquorice]

Mares Tail is one of the tough buggers, mainly beacuse the outer skin of the plant pretty water proof so the glyphosate has trouble getting into the plant in suffcient quantity. Give the plants a gentle bruising (walk on them) before spraying.

[Java Jive]

Bracken is another plant like nettles, buttercup, etc, that has natural defences against sprays - deep resilient roots, IIRC interconnecting, moderately waxy leaf surface, etc. The preferred spray against bracken used to be Asulox, which does work, if rather slowly over several seasons, but things may have moved on since then.

Certainly with bracken you need to hit it hard and above all consistently, it's no good expecting one spray to do the trick. You have to remember too that it dies back completely every year, so there's probably not much point in spraying it too late in the season. AFAICR, I used to spray twice with Asulox, once quite early in the season when the new shoots were 15-30cm above ground, again some time later, probably about mid-summer, but I can't now remember the precise recommendations for best results.

And you need to keep doing it every year, because it can take several years to exhaust the plants' systems and achieve complete kill.

When young and fit, I used to pull it out as well, but it's a hard pull, and I'd probably struggle to do it now. And aga>

[Martin Brown]

There is a very waterproof layer of silica on the outside of marestail that makes them totally impervious to weedkiller. You have to bruise it slightly before the weedkiller can have any effect at all. The roots go so deep and store so much energy that you will find it easier to move house than to eliminate this weed once it is established.

Only a concerted effort of chemical and physical attack so that no part of it ever sees daylight for long stands any chance at all.

[The Natural Philosopher]

Not so

try Glufosinate-ammonium

(DL-Phosphinothricin)

"Glufosinate is sold under trade names Basta, Buster and Liberty"

It is however quite persistent. so be careful what you plant later on.

Again, not so. It just needs the correct weedkiller.

[Steve Firth]

Fascinating.

[Martin Bonner]

(Horsetail and Mares Tail are the same thing.)

[Windmill]

Read somewhere that Roundup-resistant weeds are now a problem. And that the patent expired fairly recently. And that there is now something newer than glyphosate which does work on the resistant weeds. Suspicious persons no doubt wonder if the Roundup-resistant weeds were specially bred or modified!

[Windmill]

I'll wait a bit longer, then. The retail price of tiny sachets of already-quite-dilute glyphosate is outrageous.

[Windmill]

The back garden has become a fair imitation of wilderness, but the last time I even had a small safe fire, away from anything flammable, some busybody called the fire brigade.