Killex Lawn Weed Killer:
Tested on 12 Weed Types
Six weeks. 500 sq ft. Dandelions, clover, crabgrass, and everything in between. Here's what actually happened.
What is Killex Lawn Weed Killer?
A selective, systemic herbicide by Scotts Canada — meaning it kills broadleaf weeds while sparing grass, and works from the inside out to kill roots.
Killex is manufactured by Scotts Canada (formerly Ortho) and has been one of the most popular broadleaf weed killers in Western Canada for decades. 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 much more expensive per square foot.
Killex is selective for grass vs. broadleaf weeds — but it cannot distinguish between a dandelion and a tomato plant. Any broadleaf plant it contacts will die, including flowers, shrubs, and vegetables. Avoid spraying near garden beds, or use cardboard as a shield when spraying close to them.
Killex only works on weeds that are already growing. It has zero effect on weed seeds in the soil. If you want to prevent weeds from germinating in spring, you need a separate pre-emergent product. Use Killex to kill existing weeds, not to stop new ones from sprouting.
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Contact herbicides only kill what they physically touch. Systemic herbicides like Killex travel to the roots — that's why weeds don't just re-sprout from underground after treatment.
Active Ingredients Explained
Killex uses a three-way herbicide formula. Understanding each ingredient tells you exactly which weeds it will — and won't — kill.
Each herbicide has a slightly different mechanism. Combining them covers 50+ weed species instead of 20–30, reduces the chance of resistance, and speeds up kill time since some work faster than others.
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.
Kill Rates by Species
| Weed Species | Kill Rate | Rating |
|---|---|---|
| Dandelion | 🟢 Excellent | |
| Broadleaf Plantain | 🟢 Excellent | |
| White Clover | 🟢 Excellent | |
| Chickweed | 🟢 Excellent | |
| Ground Ivy (Creeping Charlie) | 🟡 Good | |
| Knotweed | 🟡 Good | |
| Oxalis / Wood Sorrel | 🟠 Moderate | |
| Thistle | 🟠 Moderate | |
| Bindweed | 🟠 Moderate | |
| Crabgrass | 🔴 Poor | |
| Nutsedge | 🔴 No Effect | |
| Quackgrass | 🔴 No Effect |
Despite what some product labels imply, Killex is not an effective crabgrass killer. Its three-way formula targets broadleaf weeds only. For crabgrass, you need a quinclorac-based 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.
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.
The Formula
Coverage Reference
| Killex Amount | Water Amount | Area Covered |
|---|---|---|
| 6 ml | 1 liter | 5 sq m (~50 sq ft) |
| 23 ml | 1 gallon (3.8 L) | 19 sq m (~200 sq ft) |
| 60 ml | 10 liters | 50 sq m (500 sq ft) |
| 120 ml | 20 liters | 100 sq m (1,000 sq ft) |
| Full 1L bottle | ~167 liters total | 833 sq m (~8,350 sq ft) |
Step-by-Step Application
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1Prep 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.
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2Check 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.
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3Mix 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.
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4Apply in the morning (7–10 AM) or late afternoon (4–7 PM). Midday heat causes rapid evaporation, reducing absorption and risking grass stress.
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5Hold 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.
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6Work backward from the far end. This prevents walking over freshly treated areas and tracking herbicide onto untreated grass.
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7Clean 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.
If your lawn is drought-stressed, water it lightly 24 hours before applying Killex. Well-hydrated weeds absorb herbicide 30–40% more effectively than dry, stressed plants.
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.
Safety: Pets, Kids & the Environment
2,4-D has moderate toxicity if ingested. Following re-entry guidelines is non-negotiable, especially for households with pets.
Watch for drooling, vomiting, diarrhea, lethargy, or muscle tremors. Pet Poison Helpline: 1-855-764-7661. Have the Killex label ready when you call.
Killex vs. The Competition
How does Killex stack up against the other options on the shelf?
| Feature | Killex | Weed B Gon | Roundup for Lawns | Fiesta (Organic) |
|---|---|---|---|---|
| Active Ingredients | 2,4-D + MCPP + Dicamba | 2,4-D + MCPP + Dicamba | 2,4-D + MCPP + Dicamba + Quinclorac | Iron (FeHEDTA) |
| Kills Dandelions | ✓ | ✓ | ✓ | ✓ |
| Kills Clover | ✓ | ✓ | ✓ | Partial |
| Kills Crabgrass | ✕ | ✕ | ✓ | ✕ |
| Price per Litre | $27.99 (Canadian Tire) / $39.55 (Amazon) | $22–$27 | $25–$30 | $28–$35 |
| Pet Re-Entry Wait | 24–48 hrs | 24–48 hrs | 24–48 hrs | After drying |
| Organic / Chemical-Free | ✕ | ✕ | ✕ | ✓ |
Bottom line on competitors: Killex and Weed B Gon are essentially the same product — buy whichever is cheaper. 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.
- 84% average kill rate on broadleaf weeds
- Systemic — kills roots, not just tops
- Selective — won't kill your grass
- ~$3.36 per treatment (great value)
- 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
- 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 — can't use near 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 will kill any broadleaf plant it contacts, including flowers, shrubs, and vegetables. It is selective only between grass and broadleaf weeds, not between weeds and garden plants. Keep spray at least 1–2 feet away from flower beds and vegetable gardens. On windy days, hold off entirely — drift onto a tomato plant or rose bush will kill it within days.
Spring is ideal — late April through mid-June, when soil temperatures are above 10°C and weeds are actively growing. Fall (September–October) is a close second, as weeds are moving nutrients to roots and absorb herbicide more readily. Avoid applications in hot summer weather above 30°C and never apply in winter.
The minimum is until the product has fully dried (4–6 hours for light applications in sun, 6–8 hours in shade). We recommend 24 hours. If your pet eats grass, wait the full 48 hours. Signs of 2,4-D poisoning include drooling, vomiting, diarrhea, and lethargy. Call your vet or Pet Poison Helpline (1-855-764-7661) if symptoms appear.
No — not effectively. Our tests showed only 30% kill rate on crabgrass. Killex's three-way formula targets broadleaf weeds. Crabgrass is a grassy weed, which requires a different active ingredient (quinclorac). For crabgrass, use Roundup for Lawns, Drive XLR8, or Tenacity.
The standard rate is 6 ml of Killex Concentrate per 1 liter of water. For a 1-gallon pump sprayer (3.8 L), use 23 ml. For a 2-gallon sprayer (7.6 L), use 46 ml. One full 1L bottle, properly mixed, covers approximately 833 square metres (8,350 sq ft).
No. Killex requires at least 24 hours without rain after application. Rain within that window washes the product off before it's absorbed, making the treatment ineffective. Always check a 48-hour forecast before applying, and if rain is coming, delay until you have a clear window.
Not when used as directed. Killex is selective — it's formulated to target broadleaf plants while leaving grass unharmed. It's safe for Kentucky bluegrass, perennial ryegrass, fine fescue, tall fescue, and most common lawn grasses. However, applying above 85°F, over-applying, or spraying stressed grass can cause temporary yellowing. Don't apply to newly seeded grass until it's been mowed 3–4 times.
Maximum 2 applications per year, with at least 3–4 weeks between treatments. Most lawns only need one application annually. Over-application stresses grass, builds herbicide resistance in weeds, wastes money, and increases environmental impact.
4/5 — Highly Recommended
for lawns with broadleaf weeds
At ~$3.36 per treatment, 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.
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