Not all weed killers are created equal. The wrong choice can wipe out your entire lawn while leaving the weeds untouched. Match your herbicide to your weed type for best results.
Why One Weed Killer Can't Kill Everything
Lawn weeds fall into three distinct botanical categories, and each requires a different herbicide class. Using a broadleaf killer on crabgrass will waste your money. Using a non-selective killer on your established lawn will destroy it.
Using a non-selective killer like Roundup on a lawn. It kills everything — including your grass. Always use a selective lawn-safe herbicide.
Dandelions, clover, plantain, creeping Charlie. Wide flat leaves. Killed by 2,4-D, MCPP, Dicamba (Killex, Ortho WeedClear).
Crabgrass, annual bluegrass, foxtail. Narrow blades. Need pre-emergent or Tenacity. Regular broadleaf killers won't work.
Nutsedge (yellow and purple). Triangular stems. Resistant to broadleaf herbicides. Need sedge-specific products like Sedgehammer.
Weed-by-Weed Treatment Guide
Find your weed, use the product listed.
| Weed Type | Category | Best Killer | Window | Difficulty |
|---|---|---|---|---|
| Dandelions | Broadleaf | Killex (CA) / Ortho (US) | Spring & Fall | Easy |
| Clover | Broadleaf | 3-way herbicide | Spring & Fall | Easy |
| Creeping Charlie | Broadleaf | Triclopyr-based | Spring & Fall | Moderate |
| Ground Ivy | Broadleaf | Triclopyr-based | Spring | Moderate |
| Crabgrass | Grassy | Pre-emergent | Early Spring | Hard |
| Nutsedge | Sedge | Sedgehammer | Summer | Hard |
| Plantain | Broadleaf | Killex (CA) / 2,4-D (US) | Spring & Fall | Easy |
| Chickweed | Broadleaf | 2,4-D + MCPP | Early Spring | Easy |
Never use Roundup on an established lawn unless doing a full renovation. It kills all vegetation including grass.
Selective vs Non-Selective Weed Killers
Selective herbicides kill specific plants while leaving your grass safe. Non-selective herbicides kill everything.
Selective Herbicides
- Safe for grass
- Targets specific weeds
- Killex / Ortho / Tenacity
- Apply during active growth
- Re-seed after 4-6 weeks
Non-Selective Herbicides
- Kills all vegetation
- Roundup/glyphosate
- For driveways/patios only
- Full renovation only
- Re-seed from scratch
Canada vs USA: What's Available?
Many weed killers are only sold in one country. Killex is Canada-only.
| Product | Country | Weeds Killed | Where to Buy |
|---|---|---|---|
| Killex Concentrate | Canada only | 50+ broadleaf | lawnsupply.ca |
| Ortho WeedClear | USA only | 200+ broadleaf | Home Depot |
| Spectracide Weed Stop | USA only | 200+ broadleaf + grassy | Walmart |
| Roundup for Lawns | Both | Broadleaf weeds | Canadian Tire / Home Depot |
| Tenacity | USA (online CA) | 46+ broadleaf + grassy | Amazon |
| Sedgehammer | Both | Nutsedge / sedges | Amazon |
Complete Canada vs USA guide →
Timing Your Weed Killer Application
When you apply herbicide matters. The wrong time equals wasted money.
Spring (Apr-May)
Weeds growing, soil moist, temps mild.
Early Fall (Aug-Sep)
Second flush of weed growth.
Late Winter / Early Spring
Soil temp 50-55F. Before germination.
Summer Heat / Drought
Above 27C stresses grass. Wait for cool.
Weed Prevention: Stop Them Before They Start
The best weed killer is the one you never have to use.
- Mow at correct height: 3-4 inches. Taller grass crowds out weeds.
- Overseed thin areas: Thick, dense lawn is best natural barrier.
- Improve soil health: Aerate in fall to improve drainage.
- Use pre-emergent in spring: Stop crabgrass before germination.
- Maintain lawn thickness: Regular fertilization prevents bare spots.
Lawn aeration guide | Pre-emergent herbicides
Frequently Asked Questions
Find Your Weed — Then Find Your Killer
Now that you know the three weed categories, you're ready to tackle your lawn.