Some homeowners go nuts over the sight of their lush, well-maintained lawn.
However, no one goes nuts over nutgrass.
This invasive, fast-spreading weed is notoriously difficult to control and kill. It can persist even in poor conditions and can regrow from even tiny tubers.
Nutgrass thrives in moist soil with poor drainage and full sun. It can also emerge if you have too much lawn thatch.
How to kill nutgrass in your lawn? Try one of these methods:
- Manual digging
- Selective herbicide
- Non-residual herbicide
- Tarp suffocation
- Sugar
- Vinegar
After you’ve killed off any nutgrass weed, make sure to follow proper lawn maintenance to reduce the risk of regrowth – or any other unwanted plant guests popping in.
What is Nutgrass, Anyway?
Cyperus rotundus or nutgrass (also called nut grass or nut sedge) is actually not grass (ha!). It’s a perennial plant that looks like grass, but is a member of the sedge family Cyperaceae.
Common examples of sedge weeds in Australia include nutgrass, Mullumbimby Couch, and drooping sedge. It’s most widely found in Queensland, NSW, and Victoria.
Yellow nutgrass (Cyperus esculentus) is a different plant, and its nut-like tubers are considered a delicacy in some places!
Why Nutgrass Grows in Lawns
Nutgrass prefers moist, fertile soils and full sunlight. Some factors that lead to nutgrass in your lawn include:
- Poor drainage
- Unhealthy grass
- Nutgrass in surrounding areas
- Birds pecking the rhizomes or tubers
New plants grow from the nut-like tubers found on its underground rhizomes, or from seeds blown from seed heads in other locations. You can also step on a plant and carry the seeds or tubers with you.
If you notice nutgrass starting to grow in your lawn, it’s likely the seeds or tubers have already been in the ground for a long period.
BTW – no type of lawn grass is more or less susceptible to a nutgrass invasion. Sedge weeds like nutgrass can affect buffalo, Kikuyu, couch, and most grasses in Australia.
Why is Nutgrass Bad?
By itself, nutgrass isn’t inherently bad. However, it spreads very quickly and can easily out-compete other plants in your lawn.
Nutgrass then becomes a noxious weed that eats up nutrients and space in your lawn or garden beds. It can take over your entire lawn in a matter of days or weeks.
Why Is It So Hard to Remove Nutgrass?
Unlike other weeds, nutgrass can tolerate long periods of drought, heat, or flooding. The rhizomes and tubers can go dormant for long periods, then spring back up in the right conditions.
This means that if you don’t completely remove nutgrass down to the roots and tubers, it’ll eventually grow back. Even a single stem can create a new infestation, and the roots can grow down 30cm.
Moreover, unlike annual weeds like clover or bindii, nutgrass is resistant to many chemical herbicides. It’s also strong enough to break through covers such as mulch or horticultural fabric.
Signs of Nutgrass in Your Lawn
You can identify nutgrass by the three blades that shoot up from a tuft at the base. The leaves are fairly narrow but long, reaching about 20–50cm, and will be a lighter green than your lawn.
Nutgrass plants also have reddish-brown or purplish-brown flower spikes at the end of each triangular stem. These will emerge from summer to autumn.
You might also see birds snacking on the reddish-brown tubers or rhizomes.
How to Kill Nutgrass in Your Lawn
Since nutgrass spreads so fast, it’s important to act quickly as soon as you notice even a small patch.
It’s tougher to deal with than, say, broadleaf weeds so be ready to get down and dirty.
Dig up the nutgrass plants
This will only work on a minor infestation with small plants. It’s time-consuming and tedious, but effective.
Moisten the soil with water to soften the surface. Take a garden fork or rake and loosen the soil to expose the tubers and root system.
Use a small spade (for garden beds) or shovel and dig up the ground all around the nutgrass. Go deep to make sure you take out all the rhizomes or tubers.
Check the ground for any bulbs left – even the tiniest one can lead to a new infestation.
Weed pullers won’t work in this case since uprooting nutgrass could still leave rhizomes or tubers underground.
NOTE: Do not ever put nutgrass into your compost heap. It will quickly take over and spread back to your lawn.
Instead, bag it all up (tightly!) and put it in your green bin, or soak the plants in a bucket of your chosen herbicide to kill them off.
Apply selective herbicide
Nutgrass is not a broadleaf weed, so broadleaf weed killer won’t work against it. Moreover, the glossy leaves mean many liquid herbicides may not penetrate the plant.
Look for selective herbicides that target nutgrass – usually in a wettable granular formula for better penetration.
A nutgrass herbicide that won’t kill your lawn will contain ingredients like Halosulfuron-methyl, mesotrione, and sulfentrazone.
Both SureFire Tempra Nutgrass and Mullumbimby Couch Herbicide and Amgrow Sedgehammer Herbicide are effective nutgrass herbicides that won’t kill your existing turf.
You can pair them with a wetting agent like SureFire Reactor Wetter.
Note that you may need repeated applications to get rid of all the nutgrass. Make sure to follow the manufacturer’s instructions.
Use a non-residual herbicide
For large infestations – like if your lawn has been completely overrun – you’ll need a more potent form of chemical control.
Non-selective herbicides contain glyphosate, which will kill all plants it touches – including any beneficial or desirable plants in lawns and gardens. However, they’ll kill down to the roots, preventing the risk of new or further growth.
Use non-residual weed killers like Roundup Fast-Action Weed Killer. The ready-to-use formula does not remain active in the soil, meaning you can either seed your lawn or revive the dead grass afterwards.
(So yes, Roundup does kill nutgrass if applied correctly.)
For more precise application, try a spray-type non-selective herbicide such as Roundup Natural Weed Killer or Yates Zero Ultra Tough RTU.
These are best for garden beds, where you can simply spray a small amount on the affected area while minimising contact with desirable plants.
Suffocate the weeds
This non-chemical weed control only works on a large patch of nutgrass. Moreover, it will kill all surrounding plants and may harm beneficial creatures such as worms and soil bacteria.
Start by clearing the affected area of any rocks and debris. Transplant anything you don’t want to kill.
Loosen the top layer of soil with a rake or powered garden tiller. This will expose any roots, rhizomes, and tubers under the ground.
Soak the ground thoroughly, then lay a large plastic tarp over the entire area. Secure the edges so the tarp covers the ground and will not be moved by rain or wind.
Leave the tarp for about 4 weeks. After taking it off, go through the soil to ensure there aren’t any remaining roots or tubers.
Can You Kill Nutgrass With Sugar?
Here’s a unique solution – you can get rid of nutgrass naturally using sugar!
This reportedly works because the sugar metabolises the nitrogen in the soil, depleting nutrients for nutgrass and other unwanted plants.
NOTE: Don’t use sugar in garden beds, vegetable patches, and other areas with desirable plants. It will deplete the nitrogen that these plants need to grow.
Apply the sugar in early spring, when nutgrass growth is young. For every 1 sqm of nutgrass, sprinkle about 2 kg of granulated white sugar.
Water the ground afterwards, just enough to make it damp and let the sugar seep into the soil. Too much water could wash the sugar away.
Once the nutgrass has died off, you may want to top dress your lawn or apply fertiliser to encourage the grass to grow back.
Be careful about using too much sugar – this could lead to fungal disease.
Will Vinegar Kill Nutgrass?
Yes – to a certain extent. It’s non-selective, meaning it’ll kill any surrounding grass or plants. It’s also non-residual, so it won’t fully kill off any underground rhizomes or roots.
Moreover, vinegar can alter soil pH and compromise the nutrient balance.
To make a homemade vinegar weed killer, mix 1 litre of horticultural vinegar (at least 15% concentration) with a teaspoon of dish detergent. You can add 1/3 cup of salt to make the solution more potent, as salt will enhance plant dehydration.
Transfer the solution to a spray bottle, then apply directly to nutgrass, ensuring thorough saturation.
Vinegar is most effective on young nutgrass growth. You can use it after digging up nutgrass by applying it to any regrowth.
How to Prevent Nutgrass in Your Lawn
The best way to prevent nutgrass from growing is to take proper care of your lawn or garden.
Follow best practices for lawn maintenance or work with a professional gardening service to keep your plants and grass healthy.
Ensure soil drainage
This is one crucial step to discourage nutgrass growth. Since the weed likes moist conditions, ensuring proper soil drainage lessens the chances of nutgrass, Mullumbimby Couch, and other sedge weeds from growing.
Regularly aerate your lawn to promote good drainage and air circulation. Watch for areas where standing water pools – the ground could be compacted, so the water doesn’t drain off.
Moderating lawn thatch
Thatch is good in moderation, but too much build-up can trap moisture and decrease water run-off, which encourages nutgrass growth.
If the ground starts feeling spongy or you notice unhealthy grass, it’s time to dethatch your lawn.
Letting grass grow taller
Nutgrass loves sunlight, so you can try letting your lawn grass grow taller than usual. The blades will create shade that will limit nutgrass from growing.
Remember to regularly mow your lawn, and only cut back about 1/3 of the height each time.
Apply pre-emergent herbicide
You can get ahead of nutgrass and other weeds with a pre-emergent herbicide.
These work on established lawns by preventing new growth. It’s best to apply pre-emergent weed killers in winter or spring, before the growing season.
You can look for weed-and-feed formulas that will both prevent weed growth and fertilise your lawn at the same time!
