Summer weeds

Page last updated: Thursday, 28 July 2022 - 10:50am

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Windmill grass

Windmill grass (Chloris truncata R.Br.) is a native species, and is the tenth most common summer weed species in the WA wheatbelt. Plants generally commence germination in spring, when the winter annual crops are still standing, and most seed production occurs during spring and early summer.

Windmill grass

Windmill grass plants in the wheatbelt germinate in response to spring and summer rainfall. Small plants (less than 1g dry biomass) can produce seed heads. A single seed head holds 294-522 seeds.

Plants commence germination in spring, when the winter annual crops are still standing and most seed production occurs in spring and early summer. Plant density is usually less than 20 plants per m2. Maximum seed production is approximately 60 000 seeds per m2 and maximum dry biomass production is approximately 1500kg/ha

Windmill grass may reduce crop yield potential by:

  • Utilising soil moisture and nutrients over summer/autumn that would otherwise be available to the following winter crop. The degree to which stored soil moisture from summer impacts crop yield depends on rainfall and soil type. However, windmill grass is a common summer weed on the heavier loam or clay-loam soils, which have a greater capacity to store summer soil moisture than light sandy soils.
  • Causing a delay to sowing due to the time taken to remove windmill grass in autumn.
  • Hosting crop pests or disease over summer, including aphids and the cereal leaf diseases barley yellow dwarf virus and wheat streak mosaic virus.


  • Windmill grass can be controlled by non-selective (knockdown) herbcides over summer or pre-seeding.

Windmill grass is a useful pasture species in some areas, providing forage over the summer/autumn feed gap. It is tolerant of drought and saline conditions and can be grazed heavily and repeatedly. Windmill grass growing in the central wheatbelt over summer has 61-63% digestible dry matter, 10.4-14.2% crude protein and 8.8-9.1MJ of metabolisable energy per kg dry matter.

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