At NoMoreGlyphosate.nz, we’re not just here to raise red flags — we’re here to raise awareness of safer, smarter alternatives.
A few days ago, we profiled Contact Organics, an exciting glyphosate-free solution already being used by schools and councils across New Zealand.
We’ve also recently reviewed WeedX and Weed Blast Green, two other glyphosate-free weed control options making their way into Kiwi gardens and public spaces.
Today, we’re taking a closer look at another popular choice: Slasher Organic Weedkiller. It’s fast-acting, made from natural ingredients, and backed by organic certification — making it a compelling option for anyone ready to phase out glyphosate without sacrificing results.
Why Slasher?
Slasher isn’t trying to imitate glyphosate.
It’s doing something entirely different — and it’s doing it surprisingly well.
Its active ingredients are:
- Pelargonic acid, found naturally in plants like geraniums
- D-limonene, a citrus-based oil extracted from orange peels
Together, they break down the waxy coating on weed leaves, causing them to dehydrate and collapse — sometimes within hours. Unlike glyphosate, Slasher doesn’t penetrate roots or linger in the soil.
Fast-Acting, Safe, and Certified
Slasher is BioGro certified for use in organic gardening and farming. It’s biodegradable, glyphosate-free, palm-oil-free, and contains no synthetic additives.
It’s suitable for:
- Garden beds, driveways, and fence lines
- Spot-spraying in lawns (with care)
- Schoolyards and early childhood centres
- Around fruit trees and veggie patches
For schools, councils, and early-learning providers trying to minimise chemical exposure, that certification alone is a huge plus.
Is Slasher Weedkiller Safe for Humans?
Here’s the straight answer: Slasher is considered low-toxicity compared to synthetic herbicides — but it’s still a potent formula.
Yes, Slasher is safer than glyphosate-based weedkillers in all the ways that matter:
- It breaks down quickly
- It leaves no soil residue
- It’s not systemic
- It’s approved for organic use
But “natural” doesn’t mean “harmless.”
Pelargonic acid and d-limonene can still irritate skin, eyes, and airways if you’re exposed directly.
Basic precautions still apply:
- Avoid inhaling spray mist
- Wear gloves if you have sensitive skin
- Keep kids and pets away until the leaves are dry
- Spot test surfaces to avoid staining
In short: Slasher is a much cleaner option — but still deserves the same respect you’d give any strong citrus-based cleaner.
Does Slasher Really Work?
Some natural sprays underperform.
Slasher isn’t one of them.
As long as the spray covers the plant well and conditions are dry, results appear quickly. Because it’s a contact herbicide, it only affects what it touches — and it breaks down quickly, with no long-term soil residue.
For households with pets, pollinators, veggie patches, or dirt-loving kids, that matters more than most people realise.
Why Slasher Sometimes Doesn’t Work (And How to Fix It)
No weedkiller is perfect — and Slasher is no exception.
You may need a second application if:
- The weed has deep roots
- The plant wasn’t fully covered
- Rain followed soon after spraying
- You’re dealing with hardy perennials or established grass species
And because Slasher acts on contact, any missed patches will continue growing unaffected.
It can also cause temporary staining on porous surfaces like brick or paving stones — so a small spot test is wise.
But here’s the trade-off:
You’re avoiding a chemical that’s become a global concern. No residues lingering in the soil. No synthetic compounds quietly building up over time. And for many of us, that compromise is well worth it.
Slasher Weed Killer NZ — Where to Buy It
Slasher Organic Weedkiller is available across New Zealand, including at:
- Mitre 10
- Farmlands
- PlaceMakers
- Palmers Garden Centres
- Independent garden supply stores
It comes in ready-to-use sprays for small jobs, and concentrated 500ml, 1L, and 5L bottles for larger areas.
How Slasher Compares to Glyphosate (Roundup)
Slasher and glyphosate sit in completely different categories of weed control — and that’s precisely the point.
Mode of Action: Slasher vs Glyphosate
- Slasher: Burns weeds on contact — fast and visible.
- Glyphosate: Travels systemically through the entire plant and root system.
Speed: How Fast Does Slasher Work?
- Slasher: Results in hours.
- Glyphosate: Results in days.
Soil Impact: Does Slasher Leave Residue?
- Slasher: Breaks down quickly, leaves no soil residue.
- Glyphosate: Has been detected in soil, food, water, and human urine.
We’ve also written about how glyphosate can build up in soil over time — a key difference when comparing Slasher to Roundup.
Effectiveness on Tough Weeds
- Slasher: May need repeat applications.
- Glyphosate: Kills roots but brings well-documented risks.
Safety & Health Profile
- Slasher: Low-toxicity, organic-certified, plant-based acids.
- Glyphosate: Classified in 2015 by an IARC working group as “probably carcinogenic to humans.”
If your goal is residue-free gardening — or reducing chemical exposure around kids, pets, food crops, or public spaces — Slasher stands as a far cleaner alternative.
Learn more about organic weed control solutions.
Updated 26 November 2025
This article was updated to include new alternatives and revised safety and comparison information.
Disclaimer:
This article is provided for informational purposes only and does not constitute an endorsement. We’re sharing this information to help raise awareness of glyphosate-free alternatives. No More Glyphosate NZ has no financial ties to the makers or sellers of this product. We simply believe New Zealanders deserve to know what safer options exist — and we encourage everyone to do their own homework before making changes.
Image Source & Attribution
The feature image on this page incorporates a photo by swkunst, which was then combined into a custom graphic using Canva. Explore their full portfolio here: https://www.123rf.com/profile_swkunst.
