Metsulfuron and the devastating effects it can have on your garden

Australian garden

Maintaining a healthy garden is a rewarding pursuit for many homeowners, and this upkeep goes hand in hand with the use of various tools, chemicals, and fertilisers to help control weeds and encourage plant growth. One such chemical often recommended to eradicate broadleaf weeds is metsulfuron-methyl, a powerful herbicide. However, while it may be the product of choice for many gardening pros, it can have devastating effects if used improperly. 

There are a number of key reasons metsulfuron-methyl should never be used as a herbicide in the common garden. In this blog, we’ll unpack what this herbicide actually is and does, explore why we strongly advise against ever utilising metsulfuron-methyl in such settings, and provide some alternative herbicides that may be more suitable for domestic use. 

What is metsulfuron? 

Let’s go back to the basics – what exactly is this chemical, and what does it do? Metsulfuron, or metsulfuron-methyl, is a broad-spectrum chemical widely used as a selective pre- and post-emergent herbicide in agricultural settings. It is readily available in commercial products under a range of brand names and is used to control various common brush (woody) and broadleaf weeds in winter crops, pastures, and non-crop settings such as forestry. 

It’s made from a residual sulfonylurea compound and is a systemic, foliar-active herbicide with soil residual efficacy. After it is taken up by the plant, metsulfuron works quickly and effectively. 

The herbicide is often recommended by garden experts as its efficacy rate is very high, and its cost quite low. However, using it ‘off label’ in a garden setting can be very dangerous to the health of your plants and soil, as we’ll soon find out. 

What effects can metsulfuron-methyl have on garden plants? 

Metsulfuron is extremely powerful and has the potential to kill or damage a huge variety of plants, including desirable ones like ornamental plants, flowers, fruits and veggies, and established trees. This potency – and consequently, the potential danger – can be attributed to the residual it leaves in the soil. Even after carefully targeted application, it can linger and travel to nearby areas of the soil, and may also contaminate water sources. It can also remain active in the soil for a significant period of time, which is especially dangerous in garden settings where plants are being tended to and added regularly. 

Simply put, this strong chemical can easily poison or kill more plants than you’d intend to target, hence why it poses a huge risk and is not recommended for smaller settings like gardens where plants may be arranged in close proximity. On many occasions, incorrect, off-label use of metsulfuron-methyl in a garden setting has eventuated significant plant death and even the loss of entire gardens in one fell swoop. 

Why we advise against using metsulfuron-methyl in your garden

When used as directed in safe environments, metsulfuron is a very effective herbicide that can yield fantastic results. However, the bottom line is simple – this herbicide is not intended for domestic use due to the significant risks it can pose to surrounding plants and to soil health in your garden. 

More than just a guideline, this direction is endorsed by the Australian Pesticides and Veterinary Medicines Authority (APVMA), the leading industry body. Under APVMA, metsulfuron-methyl is only registered for the control of certain broadleaf weeds in winter cereal crops, and broadleaf weeds and brush species in pastures, rights of way, commercial areas, and industrial areas. By using metsulfuron-methyl off-label – that is, going against advice on the registered label endorsed by APVMA – you are opening yourself and your garden up to dangerous results. 

In any and all circumstances, the most important step in employing a herbicide is ensuring you are adhering to the product’s guidelines for use, which will outline instructions for use, target weeds, application rates and methods, mixing instructions, precautionary statements, and more. The product label is the primary source of truth for all herbicide applications and should be consulted and followed to a tee for best results and to minimise risk. 

How to use metsulfuron safely in recommended settings

If you plan on using metsulfuron-methyl in an appropriate, approved setting, such as on winter crops, pastures, or forestry, there are a few key things to note. Most importantly, a little goes a long way. Mixing rates for metsulfuron in many high-volume sprays are often 10 grams to every 100 liters of water. If you attempt to use metsulfuron-methyl off-label in a smaller setting with a standard household pressure sprayer, this equates to 1 gram for every 10 litres of water. This can be difficult to measure properly, which is why we advise using a different herbicide more targeted to the garden environment. 

Metsulfuron-methyl is also often mixed with other chemicals as it has a synergistic effect – that is, the efficacy of both chemicals is increased when used together rather than individually. As a result, the combination of metsulfuron and another herbicide is incredibly potent and suits larger, more controlled settings very well. However, it’s no surprise that employed in the wrong situation, the outcomes of a metsulfuron-methyl mix can be severe and potentially lethal to non-target species. 

Finally, if you insist on using metsulfuron off-label, we advise covering sensitive or non-target plants with a barrier such as plastic during application, as this will minimise the risk of exposure to the chemical. However, it’s important to understand that because metsulfuron has high residual efficacy in the soil, it’s very difficult to mitigate any damage to surrounding plants, as soil can shift and kill plants unintentionally. 

What are some suitable herbicide alternatives to metsulfuron for garden use?

While metsulfuron may be a no-go, there are other herbicides that can be used to effectively remove weeds from your garden – but they too should only be employed with caution to avoid poisoning or killing non-target species. It’s also crucial to note that there’s no one herbicide on the market that is effective enough to kill every weed in your garden without destroying your trees, flowers, veggies, or herbs. 

One herbicide that may be effective in a garden setting is glyphosate. It’s a non-selective herbicide that will eradicate broadleaf weeds, but with it, can also poison or kill many other species of garden plants. It must be spot sprayed very carefully on a day with little to no wind to avoid spray drift onto non-target plants. 

There are also a number of selective herbicides, containing ingredients such as Dicamba, MCPA, and Bromoxynil, that can remove broadleaf weeds from lawns. However, be sure to select the correct herbicide for your species of lawn to ensure it’s not harmed by the application process. You can always find this information on the product label. 

Finally, if all else fails, you could always consider using an organic herbicide, as these will not cause any damage to the surrounding plants or environment. 


All in all, it’s clear that while very powerful and effective at eradicating weeds, metsulfuron should not be used in domestic situations, including gardens, under any circumstances if dire results are to be avoided. This is because of the residual nature of the chemical, which is why it is only recommended for use in larger and more controlled settings. So, when you hear a garden ‘expert’ recommending metsulfuron-methyl for use in your garden, think again, and remember the onslaught of problems this herbicide can cause in the common garden. 

While there’s no ‘silver bullet’ herbicide solution that can remove every noxious, woody, and broadleaf weed in one application, options include the careful use of glyphosate, other selective herbicides, or organic herbicides. Whatever product you choose, we recommend always researching herbicides thoroughly to understand the potential risks and benefits before application in your garden. 

Need advice on which herbicide will suit your situation best? We have over a decade of experience in the agricultural industry, advising farmers and home garden owners alike of the best products and processes to use for real results. Get in touch with the Specialist Sales team today. 

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