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Grassy Weeds in Australia: Identification and Control

Grassy weeds have leaves that are similar to the blades of grass. They are generally harder to control than broadleaf weeds.

Each year when spring arrives, it’s time for your lawn to begin its new growth after the winter dormancy.

Unfortunately, it’s also time for all those weed seeds, that have lain dormant in the soil over winter, to germinate and infest your lawn with weeds.

But before you head to your local garden centre to pick up some weed killer, it’s important to identify the type of weeds in your lawn. This will allow you to treat them effectively.

Identifying Grassy Weeds in Australia

Common lawn weeds can be grouped into two different categories, broadleaf and grassy weeds.

Broadleaf Weeds

Broadleaf weeds possess leaves that differ from ordinary grass blades. These leaves are notably wider, contributing to the weed’s distinguishable appearance.

The broader nature of these leaves makes these types of weeds comparatively easier to manage, usually with a few rounds of targeted herbicides.

The category of broadleaf weeds includes:

  • Bindii
  • Dandelion
  • Oxalis
  • Cudweed
  • Catsear
  • Soursobs
  • Chickweed
  • Clover
  • Thistle
  • Lambs tongue
  • Pennywort

Grassy Weeds

On the other hand, grassy weeds have leaves that are similar to the blades of grass.

These are somewhat harder to control because a broadleaf herbicide will not work on them.

Grassy weeds include:

  • Bahia Grass
  • Carpet Grass
  • Couch
  • Nutgrass
  • Paspalum
  • Rye Grass
  • Summer Grass
  • Winter Grass
  • Crowsfoot
  • False Onion Weed
  • Fescue
  • Guildford Grass
  • Kikuyu
  • Mullumbimby Couch

How to Control Grassy Lawn Weeds

It’s important to identify these correctly because they’ll require different treatments to eradicate them.

Let’s look into some of these grassy weeds and effective ways to control them.

Couch Grass

Couch Grass | Weed control
Couch grass / Photo by John Tann / Flickr (cropped) / CC BY 2.0

Couch grass is a pervasive weed, often sprouting up despite your best efforts to eliminate it. Its resilience and rapid underground growth make it a challenging adversary for gardeners.

Couch grass can be controlled naturally by depriving it of sunlight, using landscape fabric or a thick layer of cardboard.

A glyphosate-based product such as Roundup is the best herbicide for couch grass.

Paspalum

Paspalum dilatatum 1 | Weed control
Paspalum dilatatum / Photo by Harry Rose / Flickr / CC BY 2.0

Paspalum is a broad-leaved grass that blends easily with your lawn but becomes noticeable when it produces identifiable seed heads.

Manual removal is effective for small infestations, whereas herbicides may be required for larger ones.

Nutgrass

Cyperus rotundus nutgrass | Weed control
Nutgrass / Photo by Arria Belli / Flickr / CC BY-SA 2.0

Nutgrass, with its glossy, grass-like leaves and reddish-brown seed heads, is another challenging weed to control.

Spot treatment with a non-selective herbicide or a pre-emergent herbicide is recommended for nutgrass control.

Winter Grass

Winter Grass Poa Annua | Weed control
Winter Grass

Winter grass is an annual weed that germinates in Autumn and dies in Summer.

Although it may only live for a few months, it can spread rapidly due to its wind-blown seeds.

Manual removal can be effective for small patches, but larger invasions may require post and pre-emergent herbicides.

Onion Weed

Allium triquetrum 1 | Weed control
Allium triquetrum / Photo by Ewen Cameron (cropped) / Auckland Museum, Wikimedia / CC BY 4.0

This is another grassy weed that has long strappy leaves. These smell like onions when they’re crushed.

Onion weed will produce flowers in spring. These are normally white in colour and appear on tall stems.

Spot treating onion grass with a non-selective herbicide is the most effective way to get rid of this weed.

Weed Killers: What Works and What Doesn’t

There are basically three types of weed killers: pre-emergent, selective, and non-selective herbicides.

Pre-Emergent Herbicides

Pre-emergent herbicides are used to prevent weed seed germination. They are typically applied to the lawn before the growing season begins to prevent weed growth.

However, they do not have any effect on established weeds.

Selective Herbicides

Selective herbicides are used to kill certain types of weeds without harming the grass.

They are typically used when the weed infestation is moderate to high, and manual removal isn’t practical.

When using selective herbicides, it’s essential to follow the instructions carefully to avoid damaging your lawn.

Non-Selective Herbicides

Non-selective herbicides kill all plant life they come into contact with. These types of herbicides should only be used in extreme cases or in areas where you intend to redo the landscaping.

If you use a non-selective herbicide on your lawn, expect all vegetation, including the grass, to die.

RELATED: Complete Guide to Organic Weed Killers

Prevention is Better Than Cure

Prevention is always better than cure when it comes to weeds in your lawn.

Regular lawn maintenance practices such as proper mowing, watering, and fertilising can go a long way in preventing weed infestation.

A healthy, well-maintained lawn is the best defence against weeds. When grass is thick and lush, it leaves little room for weed seeds to take root.

If you notice a few weeds popping up here and there, it’s best to pull them up by hand before they have a chance to spread.

RELATED: The Best Homemade Weed Killers

Conclusion

Taking care of your lawn and keeping it weed-free might seem like a daunting task, but with the right tools and knowledge, it’s more than achievable.

The most crucial step is correctly identifying the type of weeds infesting your lawn, which will allow you to take the most effective course of action.

Remember, the best weed killer is a healthy lawn. So, invest time in lawn maintenance, use herbicides judiciously, and you’ll be rewarded with a beautiful, weed-free lawn.

Photo of author

Steve Kropp

Based in Melbourne, Steve's passion is vegetable gardening, and he’s been writing about it for almost 5 years. He also loves all things DIY and is always looking for a new project. When not working on his own garden projects or blogging, Steve enjoys spending time with his family, cooking meals with produce harvested from his garden, and coaching his son’s footy team.

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