Thatch grass

Thatch grass is a declared Class A and Class C weed.

Another name for this plant is Hyparrhenia rufa.

Thatch grass - infestation 

Identification

You should use this as a guide. There may be other plants or weeds that look similar.

If you are unsure, contact the Weed Management Branch.

Habit

These features describe the habit of this plant:

  • erect, densely tufted perennial grass
  • grows to 3m tall
  • mature grass can have dried tangled thatch-like tufts.

Thatch grass - habit 

Stems and branches

These features can identify the stems and branches:

  • smooth stalks
  • flower stalks are forked, with each branch of the fork growing to 4.4cm long.

Thatch grass - stems and branches 

Leaves

These features can identify the leaves:

  • smooth and flat
  • grow to 60cm long and 0.8cm wide
  • leaf-sheaths are wider than the blade at the collar base.

Thatch grass - leaves 

Flowers

These features can identify the flowers:

  • covered in rusty-brown hairs.

Thatch grass - flowers 

Fruit and seeds

These features can identify the fruit and seeds:

  • tall seed heads often form from February
  • seeds have brown bristles (awns) that are 2cm long with two bends
  • seeds are red-brown and twisted and sparsely covered with stiff hairs.

Thatch grass - fruit and seeds 

Impact

Thatch grass was previously trialled in the Northern Territory as a pasture species, but is no longer recommended or used.

Thatch grass can have all of the following impacts:

  • outcompete native grasses due to its higher germination potential and fast seedling growth
  • well-adapted to fires
  • drought tolerant and can withstand dry seasons of several months
  • can survive seasonal burning and temporary flooding.
  • can increase the fuel load and the intensity of fires, which encourages more thatch growth.

Habitat and distribution

Thatch grass is native to Africa.

It is often grown as a pasture grass in the tropics, where it has in many cases naturalised and spread beyond the original plantings.

Thatch grass is most common in the coastal districts of central and northern Queensland.

It is restricted in the NT to a small number of locations around Darwin and other parts of the Top End, especially in areas with greater than 500mm annual rainfall.

Spread prevention

After fires, thatch grass can dominate the understory replacing native vegetation, which in turn adds to the fuel load, frequency, and size of future fires. 

Seeds with long bristles are capable of catching on people or animals that walk past the plant.

The seeds are able to disperse on the wind after fires and germinate well in these conditions.

You can prevent the spread of thatch grass by doing all of the following:

  • learn how to identify thatch grass
  • map infestations to help develop a management plan
  • control minor infestations, isolated outbreaks or seedlings first
  • control plants before seeds mature
  • designate wash down areas and actively work to prevent contamination of clean areas
  • spray any plants that grow on fence lines, fire breaks and roadsides
  • make sure any hay brought into clean areas for fodder or mulch is weed free.
  • monitor areas that you have treated and watch for re-infestations.

Thatch grass - spread 

Control

Small infestations can be hand pulled. Slashing can prevent seed formation. Regrowth can then be treated with herbicide.

Chemical control

The best time to treat thatch grass is November to March. Below is a list of treatment methods that can be used.

Chemical and concentration Rate Situation, method and notes
Glyphosate 360g/L
Various trade names and formulations
2 L / 100 L Seedling or adult (individuals or infestation):
Foliar spray – apply when actively growing
Glyphosate 450g/L
Various trade names and formulations
1.6 L / 100 L Seedling or adult (individuals or infestation):
Foliar spray – apply when actively growing
Glyphosate 540g/L
Various trade names and formulations
1.4 L / 100 L Seedling or adult (individuals or infestation):
Foliar spray – apply when actively growing

Non-chemical control

Hand pulling and grubbing

Weeds, including their roots, are physically pulled out of the ground by hand or using hand tools. This is an effective method of control for individual weeds and recent outbreaks that haven’t released seeds yet, but it requires a lot of labour.

Slashing

A brush-cutter, slasher or mower are used to cut weeds off above the ground level. This can be effective in suppressing flower and seed development.

Last updated: 27 June 2017