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How to Kill Weeds in Your Lawn With the Right Herbicide

How to Kill Weeds in Your Lawn With the Right Herbicide

There's nothing more frustrating than putting time and effort into a beautiful lawn, only to look out one morning and find it riddled with weeds. Whether it's a clump of nutgrass poking through your buffalo, a carpet of oxalis taking over the back lawn, or wintergrass creeping in from the edges, knowing how to kill weeds in your lawn with the right herbicide is half the battle. The other half? Correctly identifying what you're dealing with before you reach for the spray bottle.

Patchy Australian lawn with weeds and bare brown areas mixed through green turf

Let's break down the most common lawn weeds across Australia and how to tackle each one properly.

Identifying Your Lawn Weed: Get This Right First

Lawn weed identification in Australia is a critical first step and one that many home owners skip. Using the wrong herbicide won't just fail to fix the problem, it could damage your lawn or make the weed worse.

Here's a quick guide to the usual suspects:

  • Nutgrass (Cyperus rotundus): Upright, triangular stems with a glossy appearance. It's a sedge, not a true grass, which means standard broadleaf herbicides won't touch it.
  • Oxalis (Oxalis pes-caprae / sour sob): Clover-like leaves with yellow flowers. Reproduces from underground bulbils, making it notoriously hard to eradicate.
  • Wintergrass (Poa annua): Fine-leaved, light-green clumping grass that germinates in autumn and sets seed in winter. Common in buffalo and couch lawns.
  • Crabgrass: A summer annual that spreads aggressively in warm weather. Flat, wide blades that radiate outward from a central point.
  • Invasive kikuyu: In lawns where kikuyu isn't wanted — particularly in buffalo lawns — it can be a real headache to remove without harming the surrounding turf.

Not sure which is which? Here's what each one looks like in the wild:

Nutgrass (Cyperus rotundus) plant showing the distinctive upright triangular stems and radiating brown seed heads
Nutgrass — upright, triangular stems with umbrella-like seed heads radiating from a central stalk.
Oxalis pes-caprae (sour sob) with bright yellow flowers and clover-like trifoliate leaves
Oxalis (sour sob) — bright yellow flowers above clover-like leaves. Commonly mistaken for clover.
Wintergrass (Poa annua) held next to a finger for scale, showing the fine leaves and seed heads
Wintergrass — light-green, fine-leaved clumps with distinctive branching seed heads.
Crabgrass (Digitaria sanguinalis) plant showing blades radiating outward from a single central crown
Crabgrass — flat, wide blades spreading outward from a central point in a classic star pattern.
Kikuyu grass (Pennisetum clandestinum) close-up showing fluffy white flower spikes emerging from the blades in a lawn
Kikuyu — look for fluffy white flower spikes emerging at blade height, plus aggressive runners spreading into surrounding turf.

Once you know what you're dealing with, you can choose the correct herbicide and application timing.

Broadleaf Weeds: Oxalis, Bindii and the Rest

Close-up of white clover leaves covered in water droplets — a common broadleaf weed in Australian lawns

Broadleaf weeds like oxalis, bindii, clover and thistles are some of the most common lawn complaints across Australia. The good news is that there are excellent selective herbicides available that won't harm most common lawn varieties.

Bow & Arrow is widely regarded as the industry standard for broadleaf weed control in Australian turf. It's particularly effective on oxalis weeds, and unlike some older herbicides containing only dicamba, Bow & Arrow provides longer-lasting control  meaning that even persistent weeds like sour sob are less likely to bounce back. It is labelled safe for buffalo grass varieties, which is a big deal given how many Australian homes run Sir Walter or similar buffalo lawns.

For tough or mixed broadleaf weed situations, Estate Herbicide by Syngenta offers a powerful 3-in-1 formulation combining three active ingredients for broad-spectrum control of hard-to-kill weeds. It's a great option when you're facing a variety of broadleaf invaders all at once.

And if you've ever stepped barefoot on a patch of bindii, you already know why it earns a special mention:

Dried bindii (Soliva sessilis) seed burrs nestled in lawn thatch — the infamous cause of painful barefoot encounters
Bindii seed burrs in lawn thatch — treat in late winter with a selective broadleaf herbicide, before the burrs harden.

Timing matters too. Apply broadleaf herbicides when weeds are actively growing and temperatures are mild — typically autumn or spring. Avoid spraying in the heat of summer or just before heavy rain.

Gardener applying herbicide with a pressurised hand sprayer while wearing protective gloves
Spot-spraying with a handheld pressure sprayer gives you precision and lets you avoid overspray onto lawn edges and garden beds.

Nutgrass Treatment: Why You Need a Sedge-Specific Herbicide

Nutgrass is one of the most misidentified and mismanaged weeds in Australian lawns. Because it looks grass-like, many people reach for a general herbicide and wonder why nothing happens. The answer is simple: nutgrass is a sedge, and it requires a sedge-specific product.

Sedgehammer (halosulfuron-methyl) is the go-to nutgrass treatment recommended by turf professionals and enthusiastic home gardeners alike. It's selective and safe for use in established lawns including buffalo grass. For best results, mix with a wetting agent or penetrant to help the product stick to those waxy nutgrass leaves. Apply when the nutgrass is actively growing and repeat treatments may be necessary for heavily established infestations. Browse our full herbicide range for sedge-targeting options suited to Australian lawns.

Patience is key here; nutgrass with established tubers underground won't disappear after one spray. Give it two to three weeks and be prepared to follow up.

Wintergrass and Crabgrass: Timing Is Everything

Wintergrass killer and crabgrass control are areas where application timing is absolutely critical. Both weeds are annuals, which means a well-timed pre-emergent herbicide can stop them before they even appear.

Australian Lawn Weed Control Calendar — a 12-month seasonal guide showing when to apply pre-emergent and post-emergent herbicides for each common weed
The Australian Lawn Weed Control Calendar — when to apply each herbicide type for the best result. Save or print this for your shed wall.

Pre-emergent herbicides work by creating a barrier in the soil that prevents weed seeds from germinating. For wintergrass control, apply a pre-emergent in late summer to early autumn before soil temperatures drop and germination begins. Miss that window, and you'll be chasing a post-emergent solution all winter.

Spartan Herbicide is a reliable pre-emergent option for established turf. Applied at the right time, it targets both summer and winter annual weeds, giving you a head start before seeds even get the chance to sprout. For those who want full-spectrum weed control — both before and after germination — combining a pre-emergent with a post-emergent broadleaf herbicide is a smart strategy.

For post-emergent wintergrass control, products containing pronamide (such as Amgrow wintergrass killer) are commonly recommended. Always identify that it is actually wintergrass before treating, as misidentification leads to wasted product and no results. For broadleaf weeds that often appear alongside wintergrass, Bow & Arrow is a dependable post-emergent option stocked in our range.

Kikuyu Invasion in Buffalo Lawns

Kikuyu invasion removal is a particularly tricky problem because kikuyu and buffalo are both warm-season grasses, and most herbicides that knock back kikuyu will also damage your buffalo lawn. There is no fully selective post-emergent herbicide currently registered in Australia for removing kikuyu from buffalo without some risk of turf damage.

The most practical approach involves:

  1. Manual removal for small patches: dig out the runners and rhizomes thoroughly.
  2. Edging and physical barriers to prevent encroachment from neighbouring lawns.
  3. Spot treatment with non-selective herbicides like glyphosate, carefully applied only to the kikuyu, accepting there will be a dead patch to oversow or re-turf afterwards.

Prevention through lawn health is also important. A thick, vigorous buffalo lawn is far less susceptible to kikuyu invasion than a thin, stressed one. Keep up with fertilising and watering to give your lawn the competitive edge.

Recommended Products

Here are the herbicide products we recommend for tackling the common lawn weeds covered in this article:

Sprinkler watering a lush, healthy green lawn — the goal of good lawn care

Getting on top of lawn weeds takes the right identification, the right product, and the right timing. If you're ready to take back your lawn, head over to nutrienwaterstore.com.au to browse our full range of herbicides and lawn care solutions. Our team is here to help you find exactly what you need for your lawn type and weed problem — so you can get back to enjoying a lawn you're proud of.

Image credits: Hero & clover & sprayer photos by Engin Akyurt, Hasan Albari and Gustavo Fring via Pexels. Closing sprinkler photo by Paul Moody via Unsplash. Weed identification photos: Nutgrass (Forest & Kim Starr / Wikimedia Commons, CC BY); Oxalis (Zachi Evenor / Wikimedia Commons, CC BY-SA); Wintergrass and Bindii (iNaturalist contributors / Wikimedia Commons, CC BY); Crabgrass (Wikimedia Commons, CC BY-SA); Kikuyu (Forest & Kim Starr, CC BY). Seasonal timing calendar generated using NotebookLM. Product imagery courtesy of Nutrien Water.

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