Grassy Weeds

Grassy weeds in lawns and managed turf can be difficult to remove once established. Learn how to identify and control the common grassy weeds in Australia. Learn more…

Grassy weeds, especially when present in lawns, can often be challenging to control. Unlike broadleaf weeds, which tend to contrast with the lawn, grassy weeds tend to be more difficult to spot until they become established, by which time physical removal can, at best, be time-consuming with mixed results, and at worse, not worth the effort. Treating grassy weeds with herbicide is not straightforward, since their physiology is often similar to the lawn grasses (which you obviously want to keep). Using chemicals for weed treatment in lawns need to be carried out with care; correct identification of both the grassy weed and the lawn grass present is essential, so the correct product and treatment regime can be chosen. Here we provide a quick identification and treatment guide for some of the common grassy weeds in Australia.

 

Paspalum

Paspalum (Paspalum dilatatum)
Paspalum (Paspalum dilatatum)

 

Paspalum (Paspalum dilatatum) is probably one of the easier grassy weeds to identify in that it has quite a broad leaf. Coupled with its clumping habit, it is actually quite easy to spot and is best dealt with by physical removal. For severe infestations, selective herbicides can be used to target paspalum, but these cannot be used on lawns containing warm season grasses such as buffalo, kikuyu or bahia.

 

Summer grass

Summer grass (Digitaria sanguinalis)
Summer grass (Digitaria sanguinalis)

 

Summer grass (Digitaria sanguinalis) is a clumping grass that spreads through overground runners. Its stems are brown or red in colour and produce spiky seed heads. Ideally, it would be physically removed when first spotted. Selective herbicides can be used if it is present in warm season lawns, such as buffalo and kikuyu.

 

Winter grass

Winter grass (Poa annua)
Winter grass (Poa annua)

 

Winter grass (Poa annua) comes in both annual and perennial varieties. Both produce pale-coloured seed heads, while the perennial form also produces stolons. As a weed it tends to form clumps and as it is fast growing, it will often outcompete the desired grasses. It is a cool season grass that continues growing during the winter months in Australia. However, it is relatively easy to control with selective and pre-emergent herbicides. This is one reason why winter grass is sometimes intentionally used by turf managers to overseed warm season grasses to provide colour and wear during the winter months when warm season grasses are dormant.

 

Crabgrass

Crabgrass or crowsfoot (Eleusine indica)
Crabgrass or crowsfoot (Eleusine indica)

 

Crabgrass or crowsfoot (Eleusine indica) is considered one of the worst lawn weeds globally as it spreads rapidly and produces masses of seeds. It is important to identify and remove this weed early, otherwise it can quickly take over the lawn. In the process, it kills off the lawn, a fact which becomes more apparent in winter when the crabgrass dies off leaving bare patches on the lawn. Dealing with crabgrass during the growing season is generally best achieved with a spot treatment of glyphosate followed by physical removal. Use of a pre-emergent herbicide before the start of the next growing season will provide future protection.

 

Mullumbimby couch

Mullumbimby couch (Cyperus brevifolius)
Mullumbimby couch (Cyperus brevifolius)

 

Mullumbimby couch (Cyperus brevifolius) is not actually a grass, but a sedge. It spreads through tough rhizomes and produces a round seed head, with three grass-like bracts at its base. If removing physically, it is important to ensure all the rhizomes and roots are dug up. A selective herbicide containing halosulfuron-methyl, which targets sedges, will deliver the best results (especially if applied early in the growing season).

 

Nutgrass

Nutgrass (Cyperus Rotunda)
Nutgrass (Cyperus Rotunda)

 

Like Mullumbimby couch, nutgrass (Cyperus Rotunda) is also a sedge, not a grass. It gets its name from nut-like tubers attached to its rhizomes, which sit just below the soil surface. These tubers act as an energy reserve for the nutgrass, which is one of the reasons it is difficult to control. It produces brown spiky seed heads on an upright stem. Control options are the same as for Mullumbimby couch.

 

Rye grass

Perennial ryegrass
Perennial ryegrass

 

A number of other grasses, which are used as lawn grasses, become weeds when they appear in a lawn of a different grass type. Perennial ryegrass, couch, fescue and kikuyu are common invasive lawn grasses. Couch and kikuyu with their vigorous runners are particularly aggressive. Removal of kikuyu from buffalo lawns is a painstaking process, often involving very targeted application of glyphosate to the kikuyu leaves. In other lawns, a selective herbicide can be used.

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