What's in this review

  1. What is Killex?
  2. Active Ingredients
  3. Our Test Results
  4. Kill Timeline
  5. How to Mix & Apply
  6. Best Time to Apply
  7. Safety & Pets
  8. vs. Competitors
  9. Pros & Cons
  10. FAQ
  11. Final Verdict
  12. Where to Buy

What is Killex Lawn Weed Killer?

Killex is a weed killer that targets broadleaf weeds while leaving your grass alone. It gets absorbed through the leaves and travels down to the roots, so the whole weed dies, not just the top.

Killex is manufactured by Scotts Canada (formerly Ortho) and has been one of the most popular broadleaf weed killers in Canada for decades. Homeowners from Cornwall to Toronto reach for it every spring when dandelions and clover start taking over. The word selective means it targets weeds without killing grass. The word systemic means it's absorbed through the leaves and transported through the plant's vascular system all the way to the roots, so it doesn't just burn the top, it kills the whole plant.

It comes in two formats: the Concentrate (1L) reviewed here, which you mix with water and apply with a pump sprayer, and a Ready-to-Use (RTU) version with a built-in battery-powered wand. Convenient for small spot treatments but less economical per square foot.

⚠️
Watch out for your garden beds

Killex can't tell the difference between a dandelion and a tomato plant. Any broadleaf plant it touches will die, including flowers and vegetables. Keep a bit of distance from your garden, or hold a piece of cardboard as a shield when spraying near it.

ℹ️
It won't stop weeds from sprouting

Killex only works on weeds that are already growing. If you spray bare soil, nothing happens. To stop weeds before they sprout, you need a separate pre-emergent product. Use Killex on weeds you can already see.

💡
Why this works better than most

A lot of weed killers just burn the top of the plant. Killex gets absorbed through the leaves and travels all the way down to the roots. That's why the weeds don't grow back a week later.

Active Ingredients Explained

Killex uses a three-way herbicide formula. Understanding each ingredient tells you exactly which weeds it will and won't kill.

2,4-D~5–8% concentration · The workhorse. Mimics plant growth hormones (auxins) to trigger uncontrolled, fatal growth. Has been used since the 1940s and targets dandelions, plantain, and clover.
MCPP~1–2% · Mecoprop-p. Backs up 2,4-D by targeting species that resist it alone: chickweed, ground ivy, red clover. Widens the spectrum significantly.
Dicamba~0.5–1% · A synthetic auxin targeting tough broadleaf weeds like knotweed and bindweed. Enhances root death on stubborn perennials.
🔬
Why does it use three ingredients?

Each one hits weeds in a slightly different way. Together they cover way more weed types than any single ingredient could on its own, and they work faster too.

Our Test Results

We applied Killex to a 500 sq ft section in Brandon, Manitoba on May 15, 2025 and tracked results over 14 days across 12 weed species. If your lawn looks anything like the ones we see in Bowmanville or Brantford in late spring, with heavy dandelion patches with clover creeping in from the edges. These results should feel familiar.

Location
Brandon, Manitoba
Lawn Type
Kentucky Bluegrass mix
Area Tested
500 sq ft
Mix Ratio
6 ml / 1 L water
Weather
68°F, sunny, no rain
Method
2-gallon pump sprayer
84%Overall Kill Rate
95%Dandelion Kill Rate
88%Clover Kill Rate
30%Crabgrass Kill Rate
10–14Days to Complete Kill
12Weed Species Tested

Kill Rates by Species

Weed SpeciesKill RateRating
Dandelion
95%
Excellent
Broadleaf Plantain
90%
Excellent
White Clover
88%
Excellent
Chickweed
86%
Excellent
Ground Ivy (Creeping Charlie)
78%
Good
Knotweed
74%
Good
Oxalis / Wood Sorrel
62%
Moderate
Thistle
58%
Moderate
Bindweed
55%
Moderate
Crabgrass
30%
Poor
Nutsedge
~0%
No Effect
Quackgrass
~0%
No Effect
⚠️
Heads up: Killex won't kill crabgrass

Some labels make it sound like Killex handles everything, but it doesn't touch crabgrass well. Our test showed about 30% kill rate at best. If crabgrass is your main problem, you need a different product like Roundup for Lawns or Drive XLR8.

Kill Timeline: Day by Day

Here's exactly what to expect after spraying. Don't panic if you see nothing in the first few days. Lawns in Thornhill and across the GTA typically follow this timeline closely when temperatures are in the 65–75°F range.

Days 1–2
No visible change

The herbicide is being absorbed through leaf surfaces and beginning to move through vascular tissue. Be patient.

Days 3–4
Leaves start to curl and twist

This is the herbicide disrupting auxin (growth hormone) pathways. It's a great sign that absorption was successful.

Days 5–7
Yellow discoloration and wilting

The weed's energy systems are failing. Leaves lose chlorophyll and the plant can no longer photosynthesize.

Days 8–10
Most weeds turn brown and collapse

The above-ground plant is dead or dying. Root death is occurring simultaneously in well-absorbed applications.

Days 11–14
Complete death, roots included

The weed can be safely removed. Wait 3–4 weeks before reseeding bare spots to ensure any residual herbicide has dissipated.

How to Mix & Apply Killex

Getting the mix ratio right is critical. Too weak and it won't work. Too strong and you risk grass damage.

6mlKillex Concentrate
+
1LWater
=
~5sq mCovers ~50 sq ft

Coverage Reference

Killex AmountWater AmountArea Covered
6 ml1 liter5 sq m (~50 sq ft)
23 ml1 gallon (3.8 L)19 sq m (~200 sq ft)
60 ml10 liters50 sq m (500 sq ft)
120 ml20 liters100 sq m (1,000 sq ft)
Full 1L bottle~167 liters total833 sq m (~8,350 sq ft)

Step-by-Step Application

  1. Prep the lawn 2–3 days before. Mow to normal height. This gives weeds maximum leaf surface area to absorb the herbicide. Don't scalp the lawn.

  2. Check the weather. You need temps between 60–85°F (15–29°C), no rain for at least 24 hours after spraying, and wind under 10 mph. The 48-hour window is ideal.

  3. Mix carefully. Fill sprayer halfway with water, add measured Killex, fill to final volume, shake for 30–60 seconds. Using a syringe for measurement is more accurate than eyeballing.

  4. Apply in the morning (7–10 AM) or late afternoon (4–7 PM). Midday heat causes rapid evaporation, reducing absorption and risking grass stress. In places like Peterborough, mid-May mornings are usually the sweet spot: warm enough for absorption, cool enough to avoid stress.

  5. Hold wand 12–18 inches above weeds. Use a sweeping motion. Wet foliage thoroughly but stop before runoff. You want "point of wetness," not puddles dripping off leaves.

  6. Work backward from the far end. This prevents walking over freshly treated areas and tracking herbicide onto untreated grass.

  7. Clean and label your sprayer immediately. Rinse 3 times with clean water and run water through the nozzle. Then write "HERBICIDE ONLY" in permanent marker on the sprayer. Herbicide residue sticks to plastic. Using the same sprayer for fertilizer or insecticide later can kill your plants.

💧
Quick tip: water first if it's been dry

If your lawn hasn't had rain in a while, give it a light watering the day before you spray. Weeds that are well-hydrated soak up the product a lot better than dry, stressed ones.

🌿
No-mix option: Scotts Dial 'N Spray hose-end sprayer

If you don't want to measure and mix, Killex Concentrate is compatible with the Scotts Dial 'N Spray Hose-End Sprayer (setting 6). It auto-dilutes as you spray. No tank, no math. Great for large lawns.

When to Apply: Seasonal Guide

Timing matters as much as technique. The right season can double your kill rate.

🌱 Spring
Late April – Mid June
Best Time

Weeds are young, actively growing, and haven't established deep roots. Lawns in Oakville and Waterloo are typically ready for a spring application by late April. Apply at the dandelion "rosette" stage before flowering for best results.

Expect results in 3–7 days
🍂 Fall
September – October
2nd Best

Perennial weeds are transporting energy down to roots for winter storage, so systemic herbicides travel deep into root systems for thorough kills. Apply 6–8 weeks before first frost.

7–14 days, excellent root kill
☀️ Summer
July – August
Use Caution

High heat stresses grass and causes rapid evaporation. Only apply on days under 85°F, early morning or evening. Water lawn 24 hours before. Consider reducing rate by 25% on cool-season grasses.

7–14 days (slower results)
❄️ Winter
November – March
Don't Apply

Weeds are dormant. Systemic herbicides require active plant growth to be absorbed and transported. Product will sit on the surface, wash away, and do nothing.

✕ Completely ineffective

Safety Tips: Pets, Kids & You

Killex is safe to use when you follow the label. Just keep people and pets off the lawn until it dries, and you're good. Here's the quick version.

🐾
Pets
24–48 hrs

Keep pets off the treated area until it's fully dry (at least 4–6 hours). If your dog eats grass, give it the full 48 hours just to be safe.

👦
Children
24–48 hrs

Keep kids off the lawn until dry. Rinse any outdoor toys that got sprayed, and have them wash their hands before coming inside.

🧤
While Spraying
Wear gloves

Wear gloves and long sleeves when you spray. Stay upwind so the mist doesn't blow back at you. Wash your hands well when you're done.

🐟
Near Water
Keep distance

Don't spray near ponds, streams, or ditches. And check the forecast first — if rain is coming soon, hold off and wait for a dry window.

📋
Always read the label first

The Killex label has all the details you need. It takes two minutes to read and covers mixing, safety, and what to do if something goes wrong. If your pet seems unwell after being on the lawn, call your vet or the Pet Poison Helpline: 1-855-764-7661.

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Killex Concentrate 1L
Ships Canada-wide
Killex Concentrate 1L
Kills dandelions, clover & 50+ broadleaf weeds · Ships Canada-wide
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Killex vs. The Competition

How does Killex stack up against the other options on the shelf?

FeatureKillexWeed B GonRoundup for LawnsFiesta (Organic)
Active Ingredients2,4-D + MCPP + Dicamba2,4-D + MCPP + Dicamba2,4-D + MCPP + Dicamba + QuincloracIron (FeHEDTA)
Kills Dandelions✓✓✓✓
Kills Clover✓✓✓Partial
Kills Crabgrass✕✕✓✕
Pet Re-Entry Wait24–48 hrs24–48 hrs24–48 hrsAfter drying
Organic / Chemical-Free✕✕✕✓
📊
Bottom line on competitors

Killex and Weed B Gon are essentially the same product, so buy whichever is available. If crabgrass accounts for more than 10% of your weed problem, step up to Roundup for Lawns. Fiesta is a good organic option for those who prefer a chemical-free approach.

Pros & Cons

After six weeks of testing, here's our honest assessment.

What We Like

  • 84% average kill rate on broadleaf weeds
  • Systemic: kills roots, not just tops
  • Selective: won't kill your grass
  • Great value per treatment
  • Visible results within 3–4 days
  • Simple mix ratio (6 ml/L)
  • 1 L treats 8,000+ sq ft
  • Widely available at Canadian Tire, Home Depot, RONA

What Falls Short

  • Only 30% effective on crabgrass
  • Zero effect on nutsedge and grassy weeds
  • Requires 24+ hrs dry weather (weather dependent)
  • 24–48 hr pet and child restriction
  • Toxic to aquatic life, keep away from water
  • Strong chemical odour during application
  • May need 2 applications for deep-rooted perennials

Frequently Asked Questions

The questions we get most often, answered directly.

Yes. Killex cannot distinguish between a weed and a garden plant. It is selective only in the sense that it spares grass (monocots) and kills broadleaf plants (dicots). Any flower, shrub, or vegetable it contacts will be damaged or killed. Always keep a 1–2 foot buffer from garden beds, and use a piece of cardboard as a physical shield when spraying near them.
Late spring (late April to mid-June) is ideal. Weeds are actively growing, temperatures are in the optimal 60–75°F range, and moisture levels are adequate for maximum absorption. Fall (September to October) is a close second. Perennials are moving energy to roots, which carries the herbicide deeper.
The minimum is when the product is completely dry (typically 4–6 hours). However, we strongly recommend waiting 24–48 hours, especially for dogs that eat grass. If your pet shows any signs of distress after lawn contact (drooling, vomiting, lethargy), contact your vet immediately and call the Pet Poison Helpline at 1-855-764-7661.
No, not effectively. Our field test showed only ~30% kill rate on crabgrass, and that partial result is likely due to collateral damage rather than targeted herbicide action. Killex's three-way formula (2,4-D, MCPP, Dicamba) targets broadleaf weeds. Crabgrass is a grassy weed and requires quinclorac-based products like Roundup for Lawns or Drive XLR8.
The standard ratio is 6 ml of Killex Concentrate per 1 litre of water, which covers approximately 5 sq m (50 sq ft). For a typical 2-gallon pump sprayer (7.6 L), you'll use about 46 ml of concentrate. Always measure with a syringe, eyeballing often leads to under-dosing.
No. Killex needs at least 24 hours of dry weather after application to be fully absorbed. Rain within 6 hours will wash off most of the product before it penetrates the leaves. The ideal window is 48 hours of dry weather after application. Check your forecast carefully before spraying.
At the recommended rate (6 ml/L), Killex is safe for all common Canadian lawn grasses including Kentucky Bluegrass, Creeping Red Fescue, Perennial Ryegrass, and most Bent grasses. Over-application (mixing too strong) can cause temporary yellowing. Newly seeded lawns are more sensitive, so wait until the grass has been mowed at least 3–4 times before applying.
The label allows up to 2 applications per year with a minimum of 30 days between treatments. In practice, one spring application handles most lawns. A fall follow-up treats any weeds that germinated or re-grew over summer. Avoid more frequent application as it can stress cool-season grasses and increase soil herbicide accumulation.

Final Verdict

Killex Lawn Weed Killer Concentrate 1L bottle
★★★★☆
4/5
Highly Recommended for lawns with broadleaf weeds

With an 84% kill rate on common weeds and systemic root death, Killex delivers real results for homeowners across Canada. Best for dandelions, clover, and plantain. Not suitable for crabgrass or nutsedge.

Check Price Killex VS Roundup

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Where to Buy

Killex Concentrate (1L) is widely available across Canada at major retailers. Whether you're picking it up at Canadian Tire in Whitby or ordering online, you should have no trouble finding it.

RetailerFormatNotes
Canadian TireConcentrate 1LBest in-store availability; frequent sales
Home DepotConcentrate 1LAvailable online + in-store
RONAConcentrate 1LGood Western Canada availability
Amazon.caConcentrate 1LConvenient; often Prime eligible
Lawn Supply CanadaConcentrate 1L + 500mlSpecialist retailer; bulk options

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