Roundup weedkiller Frequently Asked Questions

Why aren’t my weeds dead yet?

This is all to do with the way Roundup gets to work on weeds. The weed may look healthy still on the outside, but rest assured the plant is dying on the inside. Roundup’s systemic action sees the weed killer moving down through the plant to kill the roots. Usually, within two weeks, the leaf tips will start to wilt and turn brown. But, for larger more resistant weeds, and depending on the time of year, the process may take up to 4 weeks.

When can my children/pets return to the treated area?

When Roundup has been absorbed by the leaf, the residue will dry. When the residue has dried, children and pets can be allowed back onto the treated areas.

When can I replant/reseed after use?

Roundup is only active in plants and is inactivated on contact with the soil. It is then broken down by soil micro organisms so that you can re-use the soil for re-planting. We recommend that you leave treated weeds for about 7 days before digging or cultivating the soil to allow Roundup to move to the roots of the weed.

Why have weeds re-grown after several weeks?

Only deep-rooted rhizomatous weeds may re-grow. This will only happen if too little Roundup has been allowed to penetrate the full plant system. In this instance, a re-treatment will be required.

Roundup seems quite expensive; why is that?

While at first glance it might appear slightly more expensive than some of our competitors, Roundup actually represents excellent value for money. This is because Roundup nearly always eradicates your weed problem at first time of asking. Whereas, many other weedkillers only kill the leaves and you need to apply further treatments time and time again. With Roundup, you also get added value with many of our products. For instance, with products such as Pump ‘N Go and our new 1 litre Ready to Use ready mixed weedkillers, you have the benefits of ingenious features such as a finger guard and child security trigger.

Will it kill grass?

Yes, Roundup kills grasses very effectively. It’s ideal for killing and old lawn in preparation for laying or seeding a new one.

Why has it killed the grass?

Because Roundup is a non selective weedkiller, that means that Roundup is very effective at killing all plants. So be careful to only spray weeds or plants that you don’t want to keep.

Will it kill moss or algae?

No. For moss or algae, use a product such as Patio Magic.

Will it kill ivy weeds?

Although difficult to kill completely, you can control Ivy withy Roundup. Spray new, soft leaf growth in spring before the wax layer thickens and hardens, from May onwards, with Roundup Tree Stump & Root Killer or Roundup Ultra 3000 to directly apply where weed is too near desirable species for spraying. Where ivy is growing upwards and has a distinguishable trunk it can be cut and the freshly cut stump painted with a 20% solution of Tree Stump and Root Killer or Roundup Ultra 3000 during the dormant season between October and March.

Will it kill tough weeds such as Horsetail?

Because these weeds have leaves that are more difficult for Roundup to penetrate, you will need to adopt a programmed approach to application with repeated application at key times over the course of 2 to 3 years.

Can Roundup kill Japanese Knotweed?

Yes, but you will need to use Roundup Tree Stump & Root Killer. It may take several applications – please read the label for further advice. View our difficult weeds video guide.

Can it be used on patios?

Yes definitely, Roundup is ideal for use on Patios, Paths and drives as it penetrates right to the weeds roots to ensure a complete kill.

Does it harm the soil, persist in the soil, poison ground etc..?

Roundup is only active in plants and is inactivated on contact with the soil. It is then broken down by soil micro organisms so that you can re-use the soil for re-planting. We recommend that you leave treated weeds for about 7 days before digging or cultivating the soil to allow Roundup to move to the roots of the weed.

How long does it need before rainfall?

You may need to re-treat if it rains within 6 hours. Try to choose a day when it’s not windy and dry.

Difference between Ready to Use and Concentrate?

Roundup Liquid Concentrates need to be diluted in water before use with a dedicated garden sprayer or if you prefer a dedicated watering can. Roundup Ready to use is a already mixed for you and is available in a range of convenient sprayers.

Does the Concentrate need using up straight away after mixing?

It’s always good practice to only mix up what you need for that treatment, but you can retain the unused solution for a few weeks, but make sure that you store any weedkiller safely away from the reach of children and pets.

Can I put it on stronger? Will that work better?

We have carefully calculated the best rates at which to apply for each type of weed problem. Applying at a strong rate is not recommended and will not result in better performance. Please ensure that you read the label before use and use pesticides safely.

What are the origins of Roundup?

Roundup was first developed for the agricultural industry to help farmers overcome large-scale problems with weeds. This same science and technology has been applied to create a range weedkilling products ideal for domestic use. So, rest easy in the knowledge that you’re using the weed killer the professionals use.