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Slasher Organic Weedkiller

Slasher Organic Weedkiller

3.3 from 12 reviews

See the Best Garden Maintenance in 2019 as rated by Australians on ProductReview.com.au.

worthy of zero starts (pardon the pun)

This eco friendly product is also weed friendly. As in the photo on their website, it does indeed seem as if the weeds die in 24 hours. But guess what? Like Lazarus they rise again from the dead. Every time. Total waste of money, and it's expensive too. Back to glyphosate for me. Very disappointed.

Purchased in January 2019.

Could be cheaper but good

I still find flame weeding is the cheapest and quickest method but it does present problems for about 6 months of the year.

Compared to flaming, slasher wins on convenience (not having to lug around a 9kg propane tank and not having to worry about setting fire to things) and it loses on cost and being a bit pongy.

I would say slasher is just as effective as flaming and takes about the same amount of time - while it is expensive compared to propane, it still only costs a few dollars to weed the whole property so it is still a feasible solution.

Expensive and not really a replacement for glyphosate.

Not only is this more expensive per litre (than generic glyphosate weed killers), you also mix it at 70ml per 1 litre of water.

I bought 1 litre of Slasher from Bunnings for $29.95, a generic glyphosate weed killer (like Hortico Weed Killer 360) costs only $9.90. The Hortico 360 1 litre container can make up to 200l, the Slasher 1 litre only makes 14.3l !!! So it's comparatively extremely expensive.

Slasher does start to give visible results within a couple of hours (weeds visibly wilting), whereas glyphosate is comparatively very slow to give visible results. The Slasher hasn't been as effective with narrow leafed weeds with them not showing much (if any) visible effects after a week. A couple of Bindii weeds also seem to have survived with only some small brown patches on the leaves.

Purchased in July 2019 at Bunnings Warehouse for $29.95.

1 comment
I forgot to mention there's also a warning that Slasher may discolour pavers/ concrete. I sprayed some on charcoal concrete pavers and it's left what looks like a giant "snail track" (according to my young daughter!)

Sub par

It's great if you like the same weeds you spray come back weeks later. It doesn't kill all the roots in some weeds. It's not the silver bullet to replace Roundup (glyphosate).

Purchased in January 2019.

Organic certified products are always the best to use.

20 yrs ago approx, when operating my Landscaping/Garden maintenance business & as part of my ongoing research into organic products, I discovered Slasher. Trial & error got it right. Semi retired now & till using it at the local school where I am gardening. The extra dollars it cost is balanced by it being fast & efficient.

Purchased in January 2019 at Bunnings Warehouse for $35.00.

Its time to shift away from Glyphosate (aka Round-Up)

Been testing with this product for about a year now in varying temperatures and conditions. Professional gardener, so I use these product types regularly. It has worked fantastically in warm conditions and used it last week on a cold miserable day for the first time and it still worked great! I used some Round-Up in the same garden on the same day and a week later the weeds are barley yellowing with the standard concentration used, while at standard concentration with the Slasher, all weeds now fully dead.

You must apply a good coverage to achieve maximum results with Slasher while Round-Up acts systemicly and has a small advantage here. That said, Slasher is very fast acting and in my opinion a far superior product. Other complaints have been its a little more expensive, yes, that may be so, but the effectiveness on weeds is better and particularly for the home gardener a large bottle once a year should be plenty.

I feel now we need to be more conscience of what we are putting into the soil as a society also. Round-Up is a phosphate containing compound, which for Australian soils in particular should be avoided. So, by using this product, you are only doing your surrounding garden and environment potential damage. On top of that, we are now seeing court cases in the USA against Monsanto (the Round-Up creator). The last case (May, 2019) ordered Monsanto to pay 2 billion US dollars to the plaintiffs who have now likely obtained cancer from extensive use of this product.

Anyway, despite all this. Slasher actually works better than Round-Up.

Purchased in August 2018.

Just ok

Purchased this recently to use in my gardening business to replace round up. Extremely expensive and not as reliable but organic so that’s the plus I guess. Will give it a few more weeks.

Purchased in June 2019 at Bunnings Warehouse.

An Effective Organic Herbicide

Slasher is certified as organic and this is it's great advantage. It is expensive and difficult to use but it can be effective. It is essential to read the directions (when all else fails) as the two essential prerequisites for success are that the leaves are dry and receive a full cover. I use Slasher in the wet tropics which is a difficult area to gain control of weeds because of high moisture and plant growth.
Slasher is very effective on broadleaf plants at the 2 or 4 leaf stage and is ok on broadleaf grasses but struggles with established narrow leaf grasses and some waxy leaves. Some plants require multiple applications and it is best to reapply when the plant has used it's reserves but is only just starting to recover. this timing depends on the weather, soil health, and the physiology of the target species.
Slasher is not a panacea and is most effective when used in conjunction with other control methods - mechanical weeding, hand weeding, mowing , mulching, cover crops and shading. Nature abhors barren soil.
Well pleased with the product as it seems to have no effect on soil fertility though it may impact adversely on some ground dwelling insects.

Purchased in January 2019 at Bunnings Warehouse.

I thought it was great

Small garden and we use on driveway, stairs etc were weeds are.
Does not kill bees like toxic roundup.
We love it and were very very happy with the results , will stick with it.

Purchased in March 2019.

A useful tool that is very effective if used correctly, but disappointing if you try to use it like

The product works by drying out plant cells to induce severe moisture stress in plants. The hotter and drier the plants are, the less Slasher is required to desiccate them. Conversely, if plants are well established in warm, humid conditions then control will be more difficult.
Slasher works well on a fresh germination of plants that are all the same size, as when weeds sprout after rain on bare soil.
It can be harder to kill established plants such as caltrop that grow from a crown and couch grass that grows from runners. If they are repeatedly sprayed in hot weather they will eventually die, but that wouldn't usually be an economical control - especially if the plants have a good water source.
If attention is payed to timing in regards to weather conditions, plant growth stage and thoroughly wetting the leaf and stem surface, Slasher can be an effective, safe and profitable method of weed control for producers of high-value crops. As Slasher is really the first effective herbicide approved for use on certified organic farms, it could become a valuable part of organic food production. However, the truth is that Slasher is too expensive to even compliment other weed control methods like cultivation, mulching, crop competition and cover cropping.
I have found Slasher to be very effective if used strategically on skeleton weed in place of summer cultivation in a worked fallow, on a fresh germination of any plant after rain as the surface dries out, to suppress established weeds within wheat if applied with a shielded sprayer, and to burn off suckers under established fig trees without damaging the trees.
Personally, I think we have been spoiled by products like Roundup, that work well regardless of our laxity and remove much of the strategy and long term thinking required to work with nature in producing food instead of working against it. Roundup may be cheap and (still somewhat) effective, but what is its true cost?

Date PurchasedMay 2018

Not good enough

I sprayed Slasher in my yard and found i to be very disappointing, as some small weeds died back, a lot never lost their green look, others never changed at all. So out came Round up job done. 70 ml of slasher is way to much, but it's worse when the product doesn't work effectively you don't want to be buying a product that does not do what it claims to do.

Date PurchasedDec 2018


We would all like to use a safe weed killer in our gardens but is it cost effective to use Slasher as opposed to hand weeding and mulch. Slasher requires 70mL per litre of water compared to that much talked about glyphosate at 10mL/ litre of water. So my purchase of a 20L container of Slasher costing $300 is equivalent to spending $2100 or purchasing about 14, 20L containers of glyphosate or 175 bales of pea hay. Just to get your mind ticking over further, a major hardware store sells Slasher in a 1L container for about $20 which is equivalent to getting 14 litres of glyphosate or about 11 bales of pea hay. Keep in mind that all chemicals used by us (organic or not) need to be handled with protection and even pea hay can have an adverse effect on hay fever sufferers.

Questions & Answers

is it safe around fruit and vegetables
1 answer
Hi John, yes it is, provided you are careful to spray only the weeds. As far as experience teaches me & that fruit trees are fairly shallow rooted, Slasher will not have a harmful affect on your trees should any penetrate the ground.

Is it possible to use a surfactant with this product?
No answers

I have used slasher in the garden for about a year. Only concern is the smell that lingers in the garden for days. Is there something like eucalyptus oil that I can add to conceal the smell?
3 answers
The the active ingredient is pelargonic acid as it is produced from plants of the genus Pelargonium i.e. Geranium spp. I suggest adding Eucalyptus oil would create a smell even more stinky. DavidI have tried using detergent but concerned this will neutralise the acid and reduce effectiveness of spray. Any other suggestions?I used it for the first time 2 days ago, yes it has a strong smell but it did not smell toxic more organic. I have been extremely impressed with the results and will continue to use it.

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