July 30th, 2020 by Chris Chapman

Glyphosate is a herbicide, widely used in weedkiller. It is commonly used on farms or public fields, but it’s so effective that it’s often used in domestic gardens, too. It has a worldwide reputation as one of the fastest-acting and most effective weedkillers out there – but where does that reputation come from, and should you believe the hype?

How does glyphosate work?

Glyphosate is a non-selective herbicide, meaning that it will kill the majority of plants: great for killing any variety of weed you find in the garden but keep it away from the roses! It is what is known as a ‘systemic’ herbicide, which means it is absorbed into the vegetative parts of the plant – usually the leaves or flowers – and travels into the roots. From there, it prevents the plant from making certain proteins that are required for growth. If a plant can’t grow, it quickly dies. In scientific terminology, it stops an enzyme pathway known as the shikimic acid pathway and without this, plants and microorganisms can’t grow.

How do you use glyphosate?

Glyphosate is applied to the leaves of the weed where it is absorbed and drawn down into the roots of the plant. Systemic weedkillers like this are particularly effective because they kill the plant off at the roots and therefore prevent it from growing back. Because of this, they are ideal for controlling deep-rooted perennial weeds and will even work on notoriously stubborn weeds like Japanese knotweed and giant hogweed.

When is the best time to use glyphosate?

Because glyphosate is absorbed through leaves, it is usually best to use when leaves are at their largest and therefore have the greatest surface area. This means allowing them to grow to a decent size first. Mid to late summer is therefore often a good time to apply it (it also works best when the air temperature is above 15°C). While you may have a bit of short term pain - some unsightly weed growth for a while - you have the long term gain of preventing regrowth.

Some weeds – such as ivy – have a waxy coating on them which can prevent glyphosate from being absorbed. This means you need to do a bit of prep work before applying weedkiller. You can crush some of the leaves so they split, or cut back the ivy and allow it to regrow. After cutting, you should spray the leaves while they’re still young and growing to give yourself the best chance of success.

How can you apply it safely?

Obviously, glyphosate is a strong herbicide so it does require some caution when applying. It’s not toxic to humans and unlikely to be absorbed into skin however be careful not expose pets to it, either directly or by transfer via hands or clothing.

Wind can carry the spray to areas where you don’t want it, for example onto plants that you don’t want to kill, and rain in the first 6 hours after application would dilute it so check the weather forecast and don’t apply if it’s breezy or rain is expected. Likewise, be careful where you walk after application. Glyphosate can be tracked across your lawn or other plants on your shoes, leaving unsightly dead patches.

One of the main benefits of glyphosate is that it doesn’t contaminate soil or groundwater so you can replant the area within days of application. It actually becomes inert once it soaks into the soil, so it poses no risk to future seedlings at all.

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How soon does it work?

Glyphosate can take anywhere between a few hours to a few days to show results. It depends on the weed you’re trying to treat. Very strong, well-established weeds will take a little longer. When using glyphosate, patience is key. Because it needs to travel through the plant’s whole system and kill it from the inside, you might not see results at first. Despite this, it’ll start to work invisibly the instant it comes into contact with a plant. This means you need to be very careful where you spray it. If it comes into contact with your lawn, or with some flowers, they’re as good as dead even if you rinse it off right away.

Professional training required

Glyphosate is such a powerful, effective product that it should only be used by those with professional training. If you pick some up, you can get someone with the relevant training to apply it for you professionally – this will guarantee you get the results you’re looking for, without putting the rest of your garden at risk.