Weed

Winter grass

Poa annua

A soft, light-green grass weed that germinates in autumn, grows through winter and seeds in spring. Prevention in autumn works far better than trying to kill it once it's up.

Also called: Poa, Annual bluegrass, Wintergrass

Type
Grass weed
Lifecycle
Annual
Usually seen
Autumn to spring, most obvious in winter.

Short answer

Winter grass is a soft, light-green grass weed that germinates in autumn, grows through winter and drops seed in spring. The most effective control is a pre-emergent herbicide applied in autumn, before it germinates, using a product whose label lists your grass type. Pull or spot treat plants that come up before they set seed.

Overview

Winter grass is the most common winter weed in Australian warm-season lawns. As buffalo, couch, kikuyu and zoysia slow down in autumn, winter grass seedlings fill the gaps, and by late winter the pale tufts and seed heads are easy to spot.

Each plant can drop a lot of seed in spring, which is why winter grass comes back year after year. The most effective approach is to stop the seed establishing in the first place: a pre-emergent applied in autumn, before it germinates, plus a thick lawn that leaves little bare soil. Some types can persist as perennials in some situations, which is another reason to deal with it early.

The germination months shown are the autumn window. Timing shifts with the season and your local conditions, so treat them as a guide.

How to identify winter grass

Leaves
Soft, light-green grass leaves, paler and more tufted than the lawn around it.
Flowers and seeds
Small, whitish-green seed heads that appear through late winter and spring, even on short-mown plants.
Growth
Grows in tufts or clumps that stand out against a dormant or slow-growing warm-season lawn.
When you see it
Autumn to spring, most obvious in winter.

Look-alikes

  • Ryegrass: Ryegrass is darker green with a shiny underside to the leaf, and is often sown on purpose for winter colour.
Use the Weed Identifier

When it germinates

ZoneJanFebMarAprMayJunJulAugSepOctNovDec
Subtropical●●●
Warm temperate●●●
Temperate●●●
Cool and highland (including Tasmania)●●●
Arid and inland●●●

    What favours it

    • Thin lawns with bare soil between plants
    • Moist, shaded or compacted areas
    • Warm-season lawns slowing down in autumn, which leaves room for seedlings

    Control without chemicals first

    1. Keep the lawn thick going into autumn so there is less bare soil for seedlings.

    2. Pull or dig out small numbers of plants before they seed. Get the whole plant.

    3. Catch clippings while it is seeding, so you don't spread the seed around the lawn.

    4. Fix the conditions it likes, such as compaction and poor drainage.

    Herbicide options

    TimingActive ingredientWhat it doesGrass types
    pre emergentProdiaminePre-emergent herbicides are applied before winter grass germinates in autumn. Group 3 actives such as prodiamine, pendimethalin and dithiopyr work this way. Only products whose label lists winter grass and your grass type. (CropLife Australia)Check the label
    post emergentSee product labelSelective products that kill winter grass already growing exist for some grass types only. Labels differ in the grasses they list, so check the label lists yours.Check the label

    In the Lawn Calendar

    Pre-emergent for winter grassWeed control

    Put a pre-emergent down before winter grass germinates as the weather cools. Use a product whose label lists your grass type and winter grass, apply it at the label rate, and water it in as the label directs. Don't scarify or core afterwards unless the label allows it.

    February, March · Temperate, Cool and highland (including Tasmania)

    Pre-emergent for winter grassWeed control

    Put a pre-emergent down before winter grass germinates as the weather cools. Use a product whose label lists your grass type and winter grass, apply it at the label rate, and water it in as the label directs. Don't scarify or core afterwards unless the label allows it.

    March, April · Subtropical, Warm temperate, Arid and inland

    Stop winter grass seedingWeed control

    Pull or spot treat winter grass before its seed heads drop seed into the lawn for next year. Then plan an autumn pre-emergent.

    August, September, October · Subtropical, Warm temperate, Temperate, Arid and inland, Cool and highland (including Tasmania)

    Deal with winter weeds while they are smallWeed control

    Winter grass and bindii are easiest to dig out, or to treat with a selective herbicide whose label lists the weed and your grass, while the plants are small.

    June, July, August · Subtropical, Warm temperate, Temperate, Arid and inland, Cool and highland (including Tasmania)

    Open the Lawn Calendar

    Popular questions about winter grass

    Guides

    Common questions

    When does winter grass appear?

    It germinates in autumn, grows through winter and seeds in spring. That's why pre-emergents go down in autumn, before it comes up.

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    Sources

    1. Turf weed, pest and disease identification guide (poster), Bayer Environmental Science, hosted by Turf AustraliaWinter grass germinates in autumn, grows through winter and seeds in spring; pre-emergent applied in autumn before germination. Accessed 3 October 2026.
    2. Herbicide mode of action table, CropLife AustraliaGroup 3 pre-emergent actives. Accessed 4 October 2026.