Weeds are something that even the most dedicated lawnie has to deal with on a yearly basis. Because of this, the use of herbicides are indispensable in the battle against weeds and seasonal grasses. But for them to be most effective, you need to know when and how to use them.

How does pre-emergent herbicide work?

Pre-emergent herbicide is a herbicide used for preventative weed control and lawn health. Pre-emergents target weed seeds before they take hold, by forming a barrier at soil level that stops the germination of any new seedlings. Many also contain a fertiliser to help keep your lawn happy and healthy.

Pre-emergents can be used in the prevention of a wide range of grass weeds and broad leaf weeds. They will remain effective in your soil for around 3 months and are easy to apply seasonally to combat the different weeds that emerge throughout the year.

How to use pre-emergent herbicide

Because pre-emergent herbicides only target the seeds of weeds that are yet to germinate, the most effective way to use it is to thoroughly de-weed your lawn, then include a pre-emergent as a part of your lawn care routine. Preventing weed-seed germination is a much more effective (and healthy) way to keep your lawn weed-free all year round.

Pre-emergent comes in either a granular or liquid form and works on both broadleaf and annual grass-type weeds. It should be applied much like standard fertiliser.


Use a hand spreader (or similar) to spread it across the lawn and then water it in thoroughly.


To use a liquid pre-emergent (such as Barricade) you will need to be comfortable using a hand-sprayer. Whilst this is a more difficult application process, you do get more-bang-for-your-buck when it comes to lawn coverage.

Remember: pre-emergent herbicides require water to activate them and carry the chemical down to the root systems of newly sprouted weeds. So, after you apply pre-emergent to your lawn….WATER, WATER, WATER! 

Things you need to know about using pre-emergent herbicide

Only apply pre-emergent on established lawns. Whilst it won’t stunt the root growth of your lawn, it may cause problems for new, establishing lawns. On the same note, because pre-emergent targets the seeds that are yet to germinate, it will not be effective in irradicating already-established weeds in your lawn. These will need to be removed via different method (such as spot-spraying or hand pulling) before application.

As with most lawn products, developing a proper lawn care routine will help you get the most out of them. To be most effective, a pre-emergent herbicide should be included in your care routine in both early autumn and spring. This is because winter annual weed seeds germinate in autumn, and conversely, summer annual weed seeds germinate in spring. 

We Recommend These Products:


Barricade is a selective pre-emergent herbicide that provides residual control of weeds in established turf, garden beds and potted plants. Importantly it breaks the germination cycle of Poa annua (winter grass). It is a liquid pre-emergent, so has great coverage, but needs to be applied using a sprayer.

Barricade controls susceptible weeds by interfering with cell division in the root tips of newly germinated weeds. Barricade herbicide controls a wide range of pre-emergent grassy weeds.

You can trust Barricade to last for up to 6 months so your application window is more flexible. Barricade binds high in the soil profile ensuring turf roots below the barrier are not affected and your turf stays in prime condition.

Targeted weeds are:

  • Wintergrass
  • Crowsfoot grass
  • Crab Grass
  • Summer Grass
  • Rye Grass
  • Parramatta Grass
  • African Lovegrass
  • Broadleaf weeds including creeping oxalis, cudweed, chickweed and thistle.



Barricade is a pre emergent herbicide for grasses and broadleaf weeds including winter grass. Safe to use on all lawn varieties.

OxaFert Pre – Emergent Weedkiller


OxaFert weedkiller is a pre-emergent herbicide and fertiliser that targets weed seeds before they take hold. Targeted weeds are Broad Leaf Weeds such as bindii and flatweed, Wintergrass, Summergrass, Creeping Oxalis and Crowsfoot.

Oxa Fert

OxaFert weedkiller is a pre-emergent herbicide and fertiliser that targets weed seeds before they take hold. It does this by forming a granular film barrier at soil level that affects the germination of any new seedlings.

OxaFert weedkiller controls the emergence of weeds for up to 12 weeks, however it is recommended to reapply every eight to 10 weeks.

Targeted weeds are:

  • Broad Leaf Weeds such as bindii and flatweed
  • Wintergrass
  • Summergrass
  • Creeping Oxalis
  • Crowsfoot

Oxa Pro

Oxa Pro contains the active constituent 10g/L Oxadiazon and the added benefits of a fertiliser containing an N:P:K of 18-10-9. This combination of herbicide and controlled released fertiliser allows for pre-emergent control of Summer Grass, Crabgrass and Wintergrass in turf, whilst providing nutrition to the turfgrass, with its slow release nitrogen, phosphorus and potassium. Targeted weeds are:

  • Summer Grass
  • Crab Grass
  • Winter Grass
  • Creeping Oxalis
  • Broadleaf Weeds

Oxa Pro


Oxa Pro is for the pre emergent control of wintergrass, summergrass, crab grass and broad leaf weeds. Also contains a fertiliser.

David Grays Winter Grass Killer

This weed is difficult to control as it has built up resistance to most chemicals. It is also very active in winter, when most lawn varieties have gone dormant. Winter Grass Killer works by stunting the growth of the plant, particularly the germinating seed which will start coming up in Autumn. Having stunted or stopped the plant´s growth, it cannot spread and reproduce. Sustained treatment is required to control winter grass, and this product should not be used on Kikuyu lawns but is OK for Buffalo and Couch lawns – but always consult the label before using the product.

David Gray’s Winter Grass Killer covers approx 200m. This product will not harm the turf so it can be applied to the whole lawn. Do not use on seeded grass varieties such as rye, fescue and bent.

Targeted weeds are:

  • Winter grass


Freehand herbicide introduces a new active ingredient for use in landscape ornamentals and turf– dimethenamid-P combined with pendimethalin (that’s right – you can use it in your garden too!). Controls broadleaf weeds and grasses.

Freehand prevents weeds from growing and multiplying by inhibiting cell growth in seedling shoots and impeding plant cell microtubule assembly in roots. This powerful herbicide is labeled for the control and suppression of more than 60 of the toughest, most troublesome weeds; promoting higher quality and more marketable plants, and more attractive turf.

Targeted Weeds:

  • Summer Grass
  • Barnyard Grass
  • Chickweed
  • Fleabane
  • Blackberry
  • Cudweed
  • Creeping Oxalis
  • White Clover
  • Crowsfoot Grass
  • Paspalum
  • Dandelion

Freehand Herbicide


Freehand is a pre-emergent herbicide that prevents weeds from germinating. This powerful herbicide is labeled for the control and suppression of more than 60 of the toughest, most troublesome weeds.

Spartan Herbicide


Spartan Herbicide is a pre-emergent herbicide that can be used as an effective tool to control annual weeds (Summer & Winter).

Spartan Herbicide

Spartan Herbicide is a pre-emergent herbicide that can be used as an effective tool to control annual weeds (Summer & Winter).

Spartan Herbicide selectivity is primarily through soil profile placement. Small-seeded plants take up greater amounts of the herbicide as they germinate in the soil profile zone of herbicide placement. Warm Season grasses can be less prone to root inhibition due to the fact they have a multiple fibrous root system, hence good even coverage and incorporation is required to ensure the weeds cannot recover by establishing roots outside the zone of herbicide activity.

Application should be prior to germination of the weeds.

  • Effective against all major annual grass weeds in turf during summer and winter
  • Season-long control of annual weeds
  • Reduces future weed set and germination
  • Reduces the reliance on costly selective post-emergent herbicides
  • Unscheduled (exempt from poison scheduling)
  • Minimises nutrient and sunlight competition from annual grasses
  • Application compatibility with wetting agents
  • Low odour formulation
  • Economical solution for your main annual weed problems including African Lovegrass, Parramatta Grass, Summer Grass, Crab Grass, Crowsfoot Grass and Winter Grass
  • Flexibility to delay wash-in for a few days if necessary