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Weeds With Yellow Flowers in Australia (Identification Guide)

Weed control is a big part of lawn and garden maintenance. But what if you’re not sure what kind of weed you’re dealing with?

In this guide, we’ll help you learn more about the weeds that might be growing on your property, and educate you on weed control methods including manual removal and herbicides.

Oxalis

| Weed control
Oxalis / Photo by Zachi Evenor / Flickr / CC BY-SA 4.0

Oxalis is the bane of many gardeners. It can be extremely difficult to eradicate completely.

This weed has clover-like leaves and small yellow flowers. It multiplies through underground rhizomes and bulbs. 

This means that even if you pull it, and this is quite easy, there will still be many bulbs left in the soil that will continue to grow.

Mostly, you’ll find this weed growing in garden beds but it will also grow in your lawn.

How to control Oxalis

The most effective way to eliminate oxalis from your garden is to use a pre-emergent herbicide as pulling it out by hand will not get rid of it completely.

Capeweed (Arctotheca calendula)

Arctotheca calendula Capeweed | Weed control
Arctotheca calendula / Photo by Krzysztof Ziarnek / Wikimedia / CC BY-SA 4.0

This flatweed is common in lawns. It produces a rosette of heavily serrated leaves and a bright yellow flower with a dark centre on short stems. 

How to control Capeweed

Arctotheca calendula | Weed control
Arctotheca calendula / Photo by Harry Rose / Flickr / CC BY 2.0

Capeweed can easily be controlled by using a weeding tool to dig it out.

If your lawn is heavily infested with this weed, a broadleaf herbicide can be used to control it.

Or, you can spot treat with a glyphosate-based product if you’re careful to not get any of the product on the grass.

Dandelion (Taraxacum)

Dandelion | Weed control
Dandelion / Photo by Steffen Hammel / Wikimedia / CC BY-SA 4.0

There is much controversy around dandelion being a weed as it does have some very useful characteristics and can even be used as a herbal remedy or to make tea.

However, it’s not ideal in your lawn.

Dandelion is an opportunistic plant that will especially grow in poor soil and bare patches of ground.

It has deeply-notched leaves and produces a bright buttercup yellow flower. The fluffy seed heads are easily dispersed by wind.

How to control Dandelion

Because dandelions produce a very long tap root, they can be difficult to remove by hand.

Therefore, the most effective way to control them is to use a broadleaf herbicide.

Burr medic

Medicago polymorpha flower | Weed control
Burr Medic (Medicago polymorpha) / Photo by Krzysztof Ziarnek / Wikimedia / CC BY-SA 4.0

Burr medic is a leading cause of lawn prickles. This common lawn weed has serrated green leaves that grow together in groups of three. The creeping stems can be reddish in colour.

It produces small pea-sized flowers that are usually yellow in colour. 

Burr Medic Medicago polymorpha | Weed control
Burr Medic (Medicago polymorpha) / Photo by John Tann / Flickr (cropped) / CC BY 2.0

After flowering, the seed pods form as small green pods. These will dry out, become brown, and are prickly. The weed is spread through seed dispersal.

Medicago polymorpha fruit NC11 45869974984 | Weed control
Burr Medic (Medicago polymorpha) / Photo by Macleay Grass Man / Flickr / CC BY 2.0

Burr medic can look somewhat similar to clover and oxalis. The plant has quite a deep tap root which helps it to survive during periods of dry weather.

How to control burr medic

Burr Medic Medicago polymorpha 1 | Weed control
Burr Medic (Medicago polymorpha) / Photo by Krzysztof Ziarnek / Wikimedia / CC BY-SA 4.0

Burr medic is usually easily controlled by regular mowing. This effectively removes the flowers and seed heads or stops them from forming in the first place. 

This weed is also fairly easy to pull out by hand. However, you want to try and do this before the flowers and seed heads form. It’s a good idea to wear garden gloves when doing this.

If you have an out-of-control infestation of burr medic in your lawn, you can also kill it with an effective broadleaf herbicide such as Bow & Arrow.

Milk Thistle (Sonchus oleraceus)

Sonchus oleraceus flower | Weed control
Sonchus oleraceus / Photo by Krzysztof Ziarnek / Wikimedia / CC BY-SA 4.0

Sonchus oleraceus has many common names including common sowthistle, sow thistle, hare’s colwort, milky tassel, milk thistle, and soft thistle.

Milk Thistle is an annual plant that grows up to 1.5m tall with leaves in rosettes as well as along the stems. It is a common invasive species whose seeds can be transported by water, wind and other means.

RELATED: How to Get Rid of Weed Naturally

How to control Milk Thistle

Sonchus oleraceus | Weed control
Sonchus oleraceus / Photo by Arnim Littek / inaturalist / CC BY 4.0

Milk thistle can be controlled with manual weeding, especially if you’re able to remove the plant before it flowers. If removing plants with flowers, be very careful to not disperse the seeds.

For control of larger infestations of Milk Thistle, herbicides may be required.

Urban Bushland Council WA recommends spot spraying Lontrel (active ingredient: clopyralid) preferably at the rosette stage. They recommend applying the herbicide in the winter months for optimal treatment.

Flatweed, Catsear (Hypochaeris radicata)

Hypochaeris radicata | Weed control
Hypochaeris radicata / Photo by Harry Rose / Flickr / CC BY 2.0

Flatweed forms a flat rosette of green leaves around a central taproot, with tall stems topped by small yellow flowers.

Hypochaeris radicata rosette | Weed control
Hypochaeris radicata / Photo by Krzysztof Golik / Wikimedia / CC BY-SA 4.0

Flatweed has become known as false dandelion because people often mistake it for the true dandelion. Both plants have similar flowers and rosettes of leaves, but the stems differ.

How to control Flatweed

Hypochaeris radicata | Weed control
Hypochaeris radicata / Photo by Strobilomyces / Wikimedia / CC BY-SA 3.0

Flatweed can be removed by hand, or you can use a selective herbicide designed to eliminate them before they flower.

You can also use a non-selective herbicide like glyphosate, just don’t get any on your lawn or other plants.

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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