Mossman River Grass (Cenchrus echinatus)
Mossman River Grass is also known as Innocent Weed, Hedgehog Grass and Burr Grass. It is an upright and loosely tufted short-lived annual grass that reproduces by seeds, which are mostly spread when the spiny ‘burrs’. So its one to keep an eye out for like Caltrop.
Mossman River Grass is a weed of tropical, sub-tropical, semi-arid and arid climates that infests footpaths, urban parks, lawns, roadsides, disturbed sites, waste areas, coastal areas, waterways, wetlands, pastures and crops
The distribution map for Mossman River Grass is courtesy of The Atlas of Living Australia.
After you finish reading this, you will be able to:
- Identify Mossman River Grass, Hedgehog Grass or Innocent Weed.
- Know the habitat of Burr Grass or Hedgehog Grass.
- Know the best cultural and chemical options to control Innocent Weed or Mossman River Grass.
How to Identify Mossman River Grass.
Photosynthetic Pathway: Mossman River Grass is a C4 Weed.
Category: Grass
Flower: Mossman River Grass has a spike-like flower head that is 3 to 10 cm long. When the grass is young they are red or purple-green, but as the plant matures the flower heads become a straw or dark brown colour.
Height: This grass grows to a height of 25 to 60 cm.
Leaf length: The leaf blades of Mossman River Grass are 5 to 25 cm long and tend to have hairs along their margins. The leaf sheaths on young plants and lower stems are often red or purple.
Leaf width: The leaves of Innocent Weed are 3 to 12 mm wide.
Reproduction.
Mossman River Grass reproduces by seeds. These are encased in spiny ‘burrs’, which spread when the burrs attach to animals, machinery and clothing. These ‘burrs’ also spread in water.
As long as the area is frost free and there is adequate soil moisture, Mossman River Grass germinates and establishes all year round. However, most seeds germinate in the hot humid period of late Spring and early Summer, and then grow rapidly.
Young Mossman River Grass forms dense clumps, and produces erect flowering stems that form burrs between January and May. During the Winter most plants die, except in the tropics where it continues to grow throughout the year.
Each burr produces 3 seeds, so an indiviudal plant produces around 1000 seeds. The first seeds germinate within months, and the other two remain dormant for up to three years.
Seeds can establish from depths of up to 20 cm below the soil surface.
Comments: Because of its quick growth, Burr Grass is an aggressive competitor for light, moisture and nutrients. The spiny burrs injure and inconvenience people, and also injure horses and dogs. The fibrous roots are usually shallow but can be more than 30 cm deep.
Habitat: It is common to find Hedgehog Grass in drier regions with rainfall of 250 to 600 mm, and in sandy to light soils. You do not often find this weed grass on heavy clay soils.
For more information on weeds check out our weed ID Chart.
How to control Mossman River Grass.
You can control Hedgehog Grass by cultural and chemical means, but successful management of this weed is best if you adopt an integrated approach.
Cultural control of Mossman River Grass.
- Maintain a dense turf cover. This limits the spread of this grass because it is a weak competitor.
- Properly maintain your turf, and carry out cultural practices such as soil testing, grass selection, mowing, fertilizing and irrigation. This produces a dense, healthy lawn that prevents many weeds from becoming a problem, and that includes Burr Grass.
- If the population is not too high, hand weeding works to control this weed grass. Aim to remove all plants that are flowering offsite, rather than leave them on the ground. This ensures that no viable Mossman River Grass seed remains.
In high cut turf mowing is ineffective, because the low growing habit of Mossman River Grass, means it can produce seeds below the mowing height. However, if you are cutting below 25 mm then this can be effective to remove the seed head if you box off the clippings.
Chemical control of Mossman River Grass.
Control of Mossman River Grass works the best when it stops seeding. You will need to make several treatments to control new seedlings as they emerge. The aim is to reduce the seed bank and keep it at a low level.
Pre-emergent herbicides have been successful in the control of Hedgehog Grass in cotton, sunflowers, soybeans, pulses, lucerne and vegetables. However, these aren’t always effective due to the fact that seeds can germinate at depths of up to 20 cm.
Pre-Emergent Herbicides for Mossman River Grass.
Your best options are:
If you use these for Crowsfoot Grass or Summer Grass or Poa annua they also indirectly prevent Mossman River Grass.
Post Emergent Options.
If Burr Grass does break through your pre-emergent barrier, the next option is to use a selective post-emergent herbicide. Currently, nothing is registered in Australia for the selective control of this grass weed in turf grass. All the post emergent herbicides below are registered overseas for Innocent Weed.
Options for Mossman River Grass or Innocent Weed include:
- MSMA (ProForce Geronimo). You cannot use this on home lawns, and is not labelled in Australia for this. This is the mostmost effective if you apply it when the day time temperatures are about 24C.
- US work in couch shows that Trifloxysulfuron (ProForce Recondo) provides 4 weeks of control of Mossman River Grass but it recovers 8 weeks after treatment.
Non Selective Options.
Glyphosate works as a non selective option to control Mossman River Grass. If you use Glyphosate and water quality is an issue then we recommend the use of ProForce Manta Ray.
Other options include:
The following kill all vegetation and have a long-term residual to prevent any regrowth.
- Renegade. This stops germinating weeds for up to 12 months, and reduces the need for multiple herbicide applications.
- Numchuk Quad. Gives effective post and pre emergence weed control for up to 12 months.
- Cortex Duo. Gives a rapid knockdown of Mossman River Grass and residual control for up to 3 months. Safe to use around trees.
