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.
Category: Grass
Flower: The spike-like flower head is 3-10 cm long. When young they have a red or purple-green colour but as teh plant matures these become straw or dark brown in colour.
Height: This grows from 25 to 60 cm tall
Leaf length: The leaf blades of Hedgehog Grass are 5 to 25 cm long and usually have some hairs along their margins. The leaf sheaths on young plants and lower stems often have a reddish or purplish tinge.
Leaf width: The leaves of Innocent Weed are 3 to 12 mm wide.
Reproduction.
Mossman River Grass reproduces by seeds, 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 seed germinates within months, and the other two can 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 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:
Hand weeding is effective for the removal of Hedgehog Grass, if the population is not too high. Aim to remove all plants that are flowering offsite, rather than leave them on the ground. This ensures that no viable 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.
Chemical control of Mossman River Grass.
Currently, nothing is registered in Australia for the selective control of this grass weed in turf grass. All the chemicals discussed below are registered overseas for Innocent Weed.
Control of Mossman River Grass works the best when it prevents seeding. Repeat treatments are required to control new seedlings as they emerge, so the aim of control with this weed, is to reduce the seedbank and keep it at a low level.
Pre-emergent herbicides have been successful in the control of Mossman River 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.
In the home garden your best option is to use Onset 10GR, Echelon or Echelon Duo as the application of these for Crowsfoot Grass or Summer Grass or Poa annua will also indirectly prevent Mossman River Grass.
If Burr Grass does break through your pre-emergent barrier, the next option is to use a selective post-emergent herbicide. Options here are limited to MSMA (ProForce Geronimo), which cannot be used on home lawns, and as stated previously is not labelled in Australia for this. For this product to be most effective wait until the day time temperatures are about 24C.
US work in couch shows that Trifloxysulfuron (ProForce Recondo) provides 4 weeks of control (68% control) but it recovers 8 weeks after treatment.
You can use Glyphosate as a non selective option to control this weed. If you use Glyphosate and water quality is an issue then we recommend the use of ProForce Manta Ray.
