Lawn herbicides explained

Which selective weedkillers (herbicides) are safe on your lawn?

Weedkillers, or herbicides, keep your grass free of weeds, and a little knowledge in their use can help you avoid a disaster. Non-selective herbicides like glyphosate kill all weeds and your grass. Selective herbicides target one or a couple of types of weeds and grasses and have minimal effects on other plants and lawns.

Let’s look at some common selective herbicides and the weeds they target. We’ll also cover broadleaf herbicides, how some may be unsafe on your lawn, and why this means many Weed ‘n’ Feed type of products also may not be safe.

How to KO winter grass

Winter Grass can be removed by hand, but this can be tedious. A better option is Amgrow Chemspray Winter Grass Killer. You mix Winter Grass Killer with water to apply it. Once applied it breaks down quickly so there’s no residue left in the soil.

Winter Grass Killer kills winter grass by targeting the roots, so it’s critical to spray it early in the lifecycle of the winter grass (in May) before seed heads appear. If it goes to seed, winter grass will appear in your turf the following year and you’ll have similar problems.

Bonus tip: A pre-emergent herbicide like Oxafert targets winter grass before it emerges from the soil. Using a combination of a pre-emergent like Oxafert and a selective control like Winter Grass Killer at the right time should ensure your lawn is free of it.

How to neuter nutgrass and Mullumbimby couch

Amgrow Sedgehammer controls nutgrass and Mullumbimby couch in Sir Walter lawns and most other common lawn types. Sedgehammer is for post-emergence control, which means it works on the weeds when you can see them.

How to paralyse paspalum

Paspalum, Nutgrass & Clover Weed Killer controls paspalum. This is mixed in a pressure sprayer and the addition of a surfactant or wetting agent is recommended to ensure it adheres better to the paspalum leaf. Spraying the paspalum during the warmer months produces the best results. You may need to apply it more than once to remove it from your lawn.

For kikuyu and buffalo lawns it’s best to spot spray the paspalum and not the entire lawn as it can cause harm to your grass as well. Ensure you adhere to the application rates listed on the product.

How to blast broadleaf weeds

Selective herbicides can target bindii, clover, oxalis and many other broadleaf weeds. However, some of these aren’t safe on all grasses. The main active ingredients include dicamba and bromoxynil. Bromoxynil based herbicides, such as All Purpose Weed Control, can be used on Sir Walter buffalo, but not on older buffalo varieties such as ST buffaloes. Dicamba based herbicides can’t be used on buffalo lawns, which leads us to Weed ‘n’ Feed type products.

Why Weed n Feed is not a magic bullet

Weed n Feed products normally contain a broadleaf herbicide and a fertiliser. They come in a bottle that you attach to your hose and then spray the contents onto your lawn. This sounds good, but a product like this is like a cheap sofa bed – it doesn’t do either of its jobs remarkably well. Why? Read on.

Herbicide Component

The active constituent in Weed n Feed is Dicamba. The rate of Dicamba present in Weed n Feed bottles is very low and isn’t very effective on most broadleaf weeds (hence the very cheap price of Weed n Feed) and you will usually need 2 or 3 applications to get a result.

Dicamba cannot be used on Soft-Leaf buffalo lawns, as it will cause the lawn to die back and turn yellow. This greatly limits the products use in the domestic market as a lot of home lawns in Australia are soft leaf buffalo.

Fertiliser Component

Weed n Feed adds very little nutrient value to the grass. The fertiliser component mainly contains Nitrogen and Iron, which will give the plant a short boost of green colour, but usually contains zero Phosphorus and Potassium, so it does virtually nothing for the root strength and development of the plant. Which means it is hardly a fertiliser at all.

You’re armed, now what?

Now you know how to combat some common weeds and how to select the right product. However, there are some weeds that are difficult to control as there may be no selective herbicide available, while others that are available are extremely expensive. If you have a weed you’re unsure about call your local Lawn Solutions Australia expert in lawn care. If you’d like more information about non-selective herbicides go here.