Nutgrass
Cyperus rotundus
A sedge, not a true grass. It has shiny leaves, a triangular stem and underground tubers ("nuts") that let it regrow again and again.
Also called: Nut grass, Purple nutsedge, Nutsedge
- Type
- Sedge
- Lifecycle
- Perennial
- Usually seen
- Warm months.
Short answer
Nutgrass is a sedge, not a grass. It has shiny leaves, a triangular stem and underground tubers that let it regrow again and again. Dig out small patches with their tubers, never cultivate it through the soil, and keep the lawn thick. Selective products whose label lists nutgrass and your grass can help, but expect repeat treatment.
Overview
Nutgrass looks like a grass but is a sedge, which is why grass-weed products often don’t touch it. The giveaway is the stem: roll it between your fingers and it feels triangular.
Its strength is underground. Nutgrass builds a network of rhizomes and tubers, and every tuber can send up new shoots. That’s why digging it through the soil, or spraying once, usually ends with more of it. Patience works better: dig small patches out completely, keep the lawn thick, and if you use a product, choose one whose label lists nutgrass and your grass and expect to repeat it.
How to identify nutgrass
- Leaves
- Shiny, mid-green, grass-like leaves that grow faster than the lawn after mowing.
- Flowers and seeds
- Reddish to purplish-brown seed heads at the top of the stem.
- Growth
- Upright, from a network of underground rhizomes and tubers.
- When you see it
- Warm months.
Look-alikes
- Yellow nutgrass (Cyperus esculentus): A related sedge with straw-coloured to yellow-brown seed heads.
What favours it
- Warm weather
- Disturbed soil, where cultivation spreads tubers
Control without chemicals first
Don't rotary-hoe or dig it through the soil. Cultivation that isn't kept up spreads tubers and can stimulate growth.
Dig out small infestations, following the runners to get the tubers.
Keep the lawn thick and healthy so it competes.
Herbicide options
| Timing | Active ingredient | What it does | Grass types |
|---|---|---|---|
| post emergent | See product label | Selective products registered for nutgrass in lawns exist. Chemical control is difficult; used alone, selective herbicides are often not enough, so combine with good lawn care and expect repeat treatment. Check the label lists your grass type. | Check the label |
In the Lawn Calendar
Nutgrass grows in warm, wet conditions and comes back from underground tubers, so it takes persistence. Improve drainage where water sits, and use only products whose label lists the weed and your grass.
January, February, March, November, December · Tropical, Subtropical, Warm temperate
Nutgrass grows in warm, wet conditions and comes back from underground tubers, so it takes persistence. Improve drainage where water sits, and use only products whose label lists the weed and your grass.
January, February, December · Temperate, Arid and inland
Popular questions about nutgrass
Guides
Common questions
Why is nutgrass so hard to kill?
It stores energy in a network of underground tubers. Killing the leaves doesn't kill all the tubers, so it regrows.
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Who wrote this, and what it's based on
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Sources
- Managing garden weeds: bulbs, tubers and corms (factsheet), NSW Department of Primary IndustriesNutgrass spreads by tubers on underground rhizomes; cultivation that isn't sustained stimulates growth; selective herbicides alone are not effective enough. Accessed 4 October 2026.