How to Use Weed Killer: Tips For Beginner Gardeners

One of the most annoying aspects of gardening is those pesky weeds that keep popping up, ruining the appearance of an otherwise well-maintained outdoor space.

Unless you’re embracing the recent trend for rewilding, you’ll likely want an effective way to rid your garden of weeds. And that’s where weed killer comes in.

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What are Weeds?

Simply put, weeds are unwanted plants. They compete with other garden plants for light, water and nutrients from the soil, and can prevent desirable plants from reaching their full potential.

Weeds can grow almost anywhere and are often found in lawns, flower beds, borders, and even sprouting between paving slabs. They are generally fast-growing plants and can be unsightly, although some do have benefits, such as dandelions that provide valuable nectar for early emerging bees.

What are Weed Killers?

Weed killers, also known as herbicides, are highly effective weed control products. They are chemical solutions that work in several ways to kill weeds and help stop them from coming back.

Different types of weed killers work best on different types of weeds, and some are specifically designed for a particular area in the garden. Most gardeners use a combination of weed-killing products for the best results.

Different Types of Weed Killers


Pre-emergent herbicides are widely used to control annual and perennial weeds. This type of weed comes back year after year. Pre-emergent herbicides attack the plants’ dormant root system to prevent the weed from growing again the following spring.

This type of weed killer is usually non-selective, killing weeds and plants indiscriminately, so be careful when aiming the spray nozzle.


Post-emergent herbicides are used for killing weeds that have already germinated and emerged from the ground. Most are contact solutions that get sprayed onto the leaves of actively growing weeds.

They are generally non-selective herbicides that will kill any plant they come into contact with. For this reason, care should be taken not to accidentally spray curated shrubs and plants.

Weed and Feed

Also known as selective herbicides, weed and feed chemicals are usually used to control weeds growing in the lawn. Raising a totally weed-free lawn is almost impossible, particularly if you live in an urban area where weed seeds are easily blown between gardens. Spraying weeds with spot treatments can also kill the grass surrounding the weed.

Selective lawn weedkillers kill unwanted lawn weeds while feeding the grass to help keep it healthy.

How to Apply Weed Killer


The very first thing you should always do before applying weed killer (and even before leaving the shop) is read the label carefully. Doing this ensures you have the right weed killer for the job and tells you how to mix the solution correctly. Product labels also give you all the health and safety information you need to know. Weed killers can be dangerous, so don’t be tempted to crack on without reading and understanding the instructions.

Avoid mowing for a few days before applying lawn weed killer. Mowing cuts the leaves from the weeds, leaving less leaf surface to absorb the weed killer. This is particularly important when getting rid of broadleaf weeds because the weed killer won’t be effective if it doesn’t get enough contact with the foliage.

Check the weather forecast. Choose a still, dry day to ensure the weed killer spray doesn’t blow onto other plants or get washed off by rain before it’s had a chance to work.

Always wear protective clothing when killing weeds. The chemicals used in weed killers can cause severe skin irritation and, in the case of strong weed killer, even burns. It’s important to wear gloves, full-length trousers and a long-sleeved top. Protective eyewear is also recommended.

Pressure Sprayers

A pressure sprayer is perfect for killing many weeds in a larger area. They can hold plenty of liquid and are usually used for concentrated weed killers. A long nozzle means weeds can get sprayed from a standing position without having to bend or kneel to ground level.

Spray Bottles

Spray bottle weed killers are most often sold for domestic gardens and are ready to use. They are incredibly simple to operate – just turn the nozzle to the on position, point it at the targeted weed and press the trigger.

Watering Cans

Concentrated weed killers can be diluted and mixed in a watering can. Use a sprinkle bar or a fine rose to limit the flow. Watering cans are a cost-effective way of applying weed killer, but ensure you have two – one for killing weeds and separate watering can for tending to plants – to prevent cross-contamination. The last thing you want is for residue weed killer to kill off your best plants and flowers.

When to Use Weed Killer

Weed killers work best when the plants are actively growing, usually between May and September.

Spring is the best season to target weeds so they die before they set seed and spread further afield. Don’t rush to treat weeds in early spring, as many won’t have sprouted yet. By late spring, most weeds will have come up and will be susceptible to herbicides.

The next best time of year for killing weeds is autumn, when weeds become vulnerable as they enter their dormant period. However, by this time many weeds will have already been seeded, making the job of weeding more difficult next year.

While weed killer can be somewhat effective in summer, extreme heat and drought conditions can cause it to evaporate before it has a chance to work properly. Therefore, it’s best to apply weed killer in cooler weather.

How Long Does Weed Killer Take to Work?

Contact weedkillers start to work as soon as they come into contact with the plant. However, as they travel down the weed to kill it from the root up, you probably won’t notice much difference for at least a few days.

Yellowing and wilting weed leaves are a sure sign that the chemicals have taken effect. Weeds will usually be completely destroyed within around 4 weeks, although this depends on how strong the weed is and the type of weed killer used.

Do Dead Weeds Need to Be Pulled Out?

Yes. Leaving dead weeds in the ground is just asking for them to return the following year.

Carefully pull from the base of the plant and ensure the whole root system is pulled out and away from the soil surface. Make sure you wait until the weed has fully dried out before removing it. Doing this ensures the seeds have died and can’t create new plants.

How Often Can You Use Weed Killers?

This depends on the brand and type of weed killer, but generally, once a year is enough to keep weeds under control.

Most weeds are destroyed after the initial application, but stubborn weeds may need a second spray to finish them off. Wait around 8 weeks between applications.

Weed and feed killers can be used for lawn care up to twice per year. If the spring application is successful, there’s no need to apply weed killer again in autumn, but it is safe to do so if stubborn lawn weeds remain.

Alternatives to Weed Killers

Some gardeners consider using chemical weed killers only as a last resort, preferring natural weed control methods.

Weed by Hand

Hand weeding involves pulling or digging up weeds individually. The problem with this method is that it is difficult to wholly remove a weed’s root system. Even a tiny fragment left behind is enough for the plant to thrive again the following year. This is particularly true of weeds growing in paved areas where reach the root isn’t easy. Digging up weeds is also arduous work and can leave unsightly blemishes on the lawn.

If weeding by hand is your preferred method of weed control, use gardening gloves, grip the base of the weed and slowly pull it from the soil, ensuring as much of the root as possible is removed from the ground. You may need to use a tool to help loosen the soil around the weed but be mindful that doing this can cut some of the roots away, leaving it free to grow again.

Weed Control Fabric

Weed control fabric is an effective method to prevent weeds in paved and gravelled areas. It is perfect for use under driveways and patios. The tight-knit black fabric prevents weeds (or any other plants) from being able to grow.

Obviously, this isn’t suitable for flowerbeds or lawns, where flowers, shrubs and grass are desirable. But it does help to stop unwelcome weeds sprouting between paving slabs and stones.

Create a Wildflower Meadow

By far the easiest way to deal with weeds in your lawn is to embrace them and allow them to flourish into a wildflower meadow. This isn’t for everyone – especially not those who take pride in a well-manicured lawn – and the kids might object to losing their play area. However, it is an ideal way to boost biodiversity in the garden and ensure pollinators and other beneficial insects aren’t harmed by chemical weed control products.

No matter how well you maintain the garden, weeds are inevitable. Herbicides are a useful tool not just for annual weeds but also for stubborn perennial weeds that resurface every year. Weed and feed solutions are an excellent form of lawn care, while a spot treatment gets to work incredibly quickly.

Russell Chen

With a rich background in Horticulture from the University of Melbourne, Russell Chen has over 18 years of experience in garden design and management. He has been a key contributor to our site, after serving as a chief horticulturist at a renowned botanical garden in Australia. Russell's articles often reflect his passion for eco-friendly gardening and he has been sharing insights into sustainable gardening practices. In his leisure time, he loves exploring herbal gardening and participating in community greening projects.

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