So you’ve found yourself facing a lawn full of weeds? Weeds are pesky things that can seem impossible to control unless you equip yourself with the right knowledge.
That’s where we come in.
In this guide, we take you through the best ways to rid of a lawn full of weeds, plus how to prevent them from growing back.
Let get straight to the point. Here are five quick and simple steps to kill weeds in your lawn:
We go through each step in detail throughout the rest of the article, so keep reading!
Before dealing with a weed problem, it helps to understand the type of weeds that have invaded your lawn. And how extensive the issue is.
The methods we outline will only be effective if at least half of your lawn is healthy. If your lawn is over 50% weeds then you’re fighting a losing battle, it would be a better idea to redo your lawn completely.
There are three types of weeds:
Each weed can then be classed as either an annual, a perennial or a biennial.
Annual weeds such as crabgrass only last one season. They germinate each spring, mature over the summer and then drop their seeds before dying off in the winter. The seeds they drop will germinate the following spring, restarting the cycle.
Perennials such as dandelions don’t die at the end of summer. Over the growing season they establish strong roots that can survive the winter, allowing them to re-emerge in the spring.
Biennial weeds are less common. They grow during the first season, lie dormant for the winter and then flower and die in their second season. Thistle is an example.
The last thing to understand is when different types of weeds set. If you know this then you can target the weeds when they’re young and easier to get rid of.
When thinking about how to get rid of a lawn full of weeds, chemical herbicides might be the first thing that comes to mind. But lawn weeds are a natural occurrence, and we think it’s best to try and fight them using natural methods. Natural methods take a bit longer to get rid of weeds than using chemicals but are much better for the environment.
Manually weed removal is a selective process that you can be sure will work. Admittedly, if you have a large lawn with a significant weed problem, then it’ll be a lot of work. It’s best when dealing with annual weeds because they tend to set shallow roots that are easier to remove.
If using this method on perennials, be aware their roots will go a lot deeper. If you leave any of the roots behind, the weed will grow back. There are lots of tools available to help, such as dandelion diggers. Aim the shovel down and then angle it towards the centre of the plant pulling slowly up.
If you do notice the weed starting to grow back, pull it immediately. Eventually, you’ll get rid of even the most stubborn roots, and the weed will disappear forever.
It’s easiest to hand-pull weeds when the soil is moist. You can either wait for rain or just water the ground around the weeds yourself a few hours before removing them. Try to catch the weeds when they’re young and haven’t had a chance to seed.
They’ll be quicker to remove and won’t have had time to spread. If you notice any weeds that have flowered, snap the head off immediately to stop them spreading seeds.
Once you’re sure you’ve removed the entire weed, work some compost into the soil and reseed the bare patch.
Also, whatever you do, don’t leave the uprooted weed lying around! Otherwise, it can replant itself, and you’ll be back to square one. If the weed hasn’t seeded yet, you can throw it in your compost bin, if it has then it’s best to discard of it elsewhere.
Advocates for organic methods recommend vinegar as one of the best natural ways of killing lawn weeds. On a sunny day, it works very quickly and can kill the plant within 24 hours. Acetic acid is the active weed-killing ingredient. It works by burning the leaves of the weed, causing them to wither and die.
The downside to using vinegar is that it won’t directly kill the roots of the plant. However, without leaves for photosynthesis, the roots won’t be able to survive.
Also, it’s not selective so can kill your grass without careful application. You might need to apply the vinegar multiple times to more hardy weeds, but with repeated spraying, it should eventually kill any weed.
Household vinegar has a concentration of about 5% acetic acid. This is quite low and won’t be very effective on its own, especially on older weeds.
To see results you need a vinegar with at least 10-20% acetic acid concentration.
Green Gobbler’s 20% vinegar weed killer is certified organic and kills weeds in less than 24 hours. Make sure you wear protection when using a concentrated vinegar because it can burn human skin.
You might see some recipes add salt. Adding salt can improve the potency of less concentrated vinegar. It works by drawing moisture out of the weed but will quickly leach into the soil and sterilize it. If the salt concentration in your soil is too high, nothing (including grass) will grow there. For this reason, we don’t recommend using it on your lawn. Only use salt if you’re killing weeds on a patio or driveway.
The dishwashing liquid acts as a surfactant allowing the vinegar to penetrate the waxy exterior of the weeds.
To avoid killing the grass, apply the mixture with a precise spray bottle.
If you want to be even more careful, you can coat the weeds with a paintbrush. Avoid applying the vinegar before it rains so it doesn’t get washed away. As we mentioned earlier, a sunny day is best because it enhances the burning effect.
You can use corn gluten as an organic pre-emergent herbicide for crabgrass and other weeds. It won’t stop the weeds from germinating, but it inhibits root development.
We recommend Espoma’s weed preventer. It’s made from 100% corn gluten.
Application of corn gluten needs to be carefully timed. The best time to apply it is just as the seeds start to germinate. After application, the herbicide needs watering in. Once applied, it requires a dry period of a few days, so you’ll need the weather to work in your favour here.
Corn gluten contains high levels of nitrogen, so it also acts as a fertilizer. This is good news if it’s applied correctly because it will fertilize the grass. However, if you’ve applied it too late and the crabgrass has already established roots, then it’ll fertilize the weeds and make the problem worse.
If all else fails, or you’re desperately in need of a quick method, then you should look at chemical weed killers. There’s lots of choice on the market, but most are well labeled and make it clear which weeds they work against.
They come in two main types:
Pre-emergent treatments like Scotts weed preventer tackle weeds before they emerge. They’re very effective on crabgrass. You can apply them as a preventative measure if you know you have a particular area of the lawn that’s prone to weed growth.
Post-emergent treatments are for killing established weeds. You can get either selective or non-selective types.
Selective options are very targeted and work for specific weeds. They make very effective spot treatments for stubborn perennials. Ortho weed B gone weed killer kills 250 types of weed without harming the lawn.
Non-selective killers like Compare ‘N Save’s weed and grass killer are only really a good idea if you plan to reseed the lawn afterward as they kill everything they touch.
You also need to pick between contact and systemic. Contact weed killers work like vinegar and only kill the weed above ground. Systemic herbicides circulate inside the plant and kill the whole thing, including the roots.
A healthy lawn is key to preventing weeds from overtaking. Weeds only thrive when the grass is struggling. Weak stressed out lawns become thin and patchy, leaving plenty of space for weeds to grow.
Here are five lawn care tips to help you maintain a healthy lawn:
Overseeding is an essential part of lawn care that lots of homeowners miss out. It’s the process of laying new grass seed on your existing lawn and is one of the best ways to keep your lawn thick, green and free from weeds.
Grass types are always improving. Overseeding gives you a chance to introduce newer grass varieties into your lawn that have enhanced weed fighting properties.
The shorter you mow your lawn, the more water and sunlight weed seeds will get, helping them to grow.
Tall grass will shade the seeds meaning they’re less likely to germinate. We recommend keeping your lawn between 2-4 inches high and to time mows so that you remove no more than 1/3 of the total grass height.
Your watering pattern will determine the type of roots your turf develops. Shallow watering leads to shallow roots that leave your lawn vulnerable to drought and thinning. Damaged, thin lawns make it easy for weeds to take over.
Not watering your lawn enough means that the weeds will take it all and leave none for your grass.
Instead, you should aim to water deeply, but less frequently. This will encourage the grass seed to develop deep roots.
Deep-rooted grasses are better able to out-compete weeds. Most lawns need about an inch of water once a week. A useful tip is to put an empty tuna can on your lawn to help you determine when you’ve applied enough water.
Fertilizing your lawn is a delicate balancing act. If you don’t fertilize enough, then the weeds can become stronger than the grass and start to overtake.
Too much fertilizer and you risk burning your lawn while feeding the lawn weeds and help them flourish.
How much and how often you should fertilize depends on your lawn type. We recommend using an organic lawn fertilizer such as compost. It’s free to make, reduces food waste, and won’t cause any environmental or long term damage.
Thatch is a layer of decaying organic debris that lies on top of your soil. A thin layer less than 1/2 an inch thick is beneficial for the turf and acts as mulch. However, if the coating gets too thick, then it can become a barrier that absorbs all the water and inhibits grass roots from developing.
Dethatching removes the layer of debris. You can do it manually or with machines like power rakes and vertical mowers.
Aeration is a process to loosen soil that’s become overly compact. Compact soil is common in sandy soil types, or if your lawn gets a lot of footfall. When soil is too dense, it can limit the movement of air and water and therefore, nutrients. This prevents the grass from accessing what it needs. And with your lawn in a weakened state, weeds can thrive.
Hopefully, our tips have supplied you with the knowledge of how to get rid of a lawn full of weeds.
Once you’ve dealt with the initial problem, the best way to get rid of weeds is to keep your lawn healthy.
Another common lawn pest is insects. If your lawn also has a bug problem be sure to take a look at our roundup of the best lawn insect killer granules.
Veronica has a passion for all things eco-friendly. After growing up on a farm in Ireland, she went on to study Chemistry and Environmental Sciences. Veronica has also volunteered in many sustainability roles, including conservation efforts in Bangladesh and teaching Environmental Sciences to schoolchildren in Kenya.