Winter Grass (Poa Annua) Control: Preventing and Killing This Lawn Weed
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Time to read 5 min
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Time to read 5 min
Winter Grass (Poa annua) is one of the most frustrating lawn weeds for Australian homeowners. It sneaks into your lawn in the cooler months and spreads quickly, creating unsightly light green patches that stick out like a sore thumb—especially in couch, kikuyu and buffalo lawns.
In this guide, we’ll break down exactly what winter grass is, how to control it once it shows up, and—more importantly—how to prevent it from returning next year.
Winter Grass, or Poa annua, is a soft, cool-season weed that appears in lawns across Australia during autumn and winter. It thrives when your couch, buffalo or kikuyu lawn slows down, filling in gaps and creating a patchy, uneven look.
Pale, light green colour that stands out against your lawn
Grows in clumps with soft, fine leaves
Produces small white seed heads — even when mown short
Appears in shaded, damp or compacted areas
Spreads rapidly once established
It’s a seasonal weed, but if allowed to seed, it’ll return stronger year after year — making control and prevention absolutely essential.
While it may not seem aggressive at first, winter grass can take over large sections of lawn during the cooler months. Here’s why you want it gone:
Visual Disruption – It breaks up the uniform colour and texture of your turf
Spreads Easily – One plant can produce thousands of seeds
Weakens Your Lawn – Competes for water, nutrients, and light
Dies Off in Spring – Leaving unsightly bare patches just as your lawn should be bouncing back
Hard to Kill When Mature – Many herbicides are less effective after seeding
For lawns that you’ve worked hard to maintain, winter grass can undo months of effort if not addressed early.
Depending on whether winter grass is already present or you’re aiming to stop it before it starts, there are two main approaches: post-emergent and pre-emergent control.
If winter grass is already growing in your lawn, you’ll need a selective post-emergent herbicide that targets Poa annua without damaging your turf.
Here are two trusted options:
Great for warm season lawns
Slows growth and kills winter grass over 2–4 weeks
Apply during cooler months for best results
Ensure even coverage and water in as directed
Also effective for targeting ryegrass and early-stage winter grass
Won’t harm your warm-season turf
Apply early in the weed’s life cycle for best results
TIP: Avoid mowing immediately before or after applying herbicides. Let the product absorb fully for maximum effectiveness.
If you’ve dealt with winter grass in the past, the most effective strategy is to prevent it before it appears. Pre-emergent herbicides work by forming a barrier in the soil, stopping seeds from germinating in the first place.
Best applied in late summer to early autumn (Feb–March)
Apply before soil temps fall below 16°C
Safe for buffalo, couch, kikuyu, and zoysia
Lasts for up to 6 months when applied correctly
Application Rate:
Use 40mL per 100m²
Water in lightly after application
Reapply every 6 months for continued protection
REMEMBER: Pre-emergents won’t kill existing weeds — only prevent new ones. That’s why timing is critical.
In addition to chemical control, cultural practices make a big difference in keeping winter grass at bay:
The best defence is a dense lawn that leaves no room for weeds
Mow regularly and keep your turf strong with proper fertilising
Dominate Fertiliser – Ideal for growth and resilience
Proliferate – High-performing maintenance fertiliser
Apply every 6–8 weeks during the growing season
Winter grass thrives where your lawn struggles
Aerate compacted soil annually
Thin out heavy shade if possible or raise mowing height to help your turf compete
Shallow, frequent watering encourages weed seeds to germinate
Water deeply 2–3 times per week to encourage deep root growth in your turf
Month |
Action |
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February |
Apply Spartan pre-emergent herbicide |
March–April |
Monitor lawn health, mow regularly, fertilise |
May–June |
Watch for signs of winter grass, spot treat with Propyzamide or Odessa |
July–August |
Continue mowing and treating as needed |
September |
Winter grass will die off — patch repair as needed |
October |
Overseed or topdress if bare spots are left |
A: Yes, it typically dies in spring, but it drops seeds first, meaning it’ll come back stronger next year if left untreated.
A: No — Bow and Arrow is great for broadleaf weeds (like clover and bindii) but ineffective on winter grass.
A: Yes, Spartan is safe for all major Australian lawn types, including buffalo, couch, and kikuyu.
A: Yes, you can apply both, but do not mix them together in the same sprayer unless the label specifically allows it.
Prevents winter grass from germinating |
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Kills visible winter grass |
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Controls early-stage winter grass and ryegrass |
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Strengthens lawn to outcompete weeds |
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Excellent for regular maintenance |
Winter Grass (Poa annua)is a cool-season weed that thrives in Aussie lawns during autumn and winter, especially in couch, kikuyu and buffalo.
Post-emergent herbicides like Propyzamide 500 and Odessa can kill visible winter grass without damaging your turf.
Pre-emergent herbicides like Spartan are the best way to prevent winter grass before it germinates.
Cultural practices like regular mowing, deep watering, aeration, and using quality fertilisers (like Dominate and Proliferate ) help your lawn stay dense and weed-resistant.
Timing is everything — apply pre-emergent in late summer (Feb–March) and spot-treat new growth early before it seeds.
Pair chemical control with lawn health strategies for year-round protection.
Winter grass might be a persistent weed, but it’s far from unbeatable. With a proactive pre-emergent strategy and the right spot treatments in winter, you can keep your lawn looking lush and weed-free all year round.
If you’re just starting out or not sure what to do next, grab our Free Lawn Calendar — it gives you a simple, month-by-month plan tailored for Aussie conditions.
The Author: Ben Sims
Ben Sims is a passionate greenkeeper turned lawn care expert. With years of experience in greenkeeping, he's shifted his focus to helping homeowners achieve their dream lawns. Through his website and YouTube Channel, Lawn Tips, he shares practical advice, comprehensive lawn care plans, and high-quality lawn products to make lawn maintenance more straightforward and effective.
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