What's in this guide
You've got weeds. You've heard of Killex and Roundup. Now you're trying to figure out which one to buy. It's a good question — and the answer is simpler than you might think.
Both products work well. But they do very different things. Using the wrong one can kill your grass, waste your money, or leave you with the same weeds next week.
This guide explains what each one does, when to use it, which one to buy, and where to get it.
The Most Important Thing to Understand First
Before anything else, you need to know this one fact:
Killex only kills weeds — it leaves your grass alone. You can spray it across the whole lawn and nothing happens to the grass. Roundup kills everything it touches — grass, weeds, flowers, vegetables. If it lands on a plant, that plant will die.
That one difference tells you everything you need to know. Killex is for lawns. Roundup is for driveways, paths, and areas where you want to clear everything out. Simple as that.
What Is Killex?
Killex has been one of the top lawn weed killers in Canada for decades. It's a concentrate — you mix it with water, put it in a sprayer, and spray it on your lawn.
It works by getting into the weed through its leaves and attacking it from the inside out — all the way down to the roots. The weed dies completely. Your grass is not affected at all.
Dandelions, clover, plantain, creeping Charlie, ragweed, and 50+ other common weeds will be dead within 1 to 2 weeks. Your lawn keeps growing like nothing happened.
What Killex Kills Well
- Dandelions
- Clover (white and red)
- Plantain
- Ground ivy (creeping Charlie)
- Chickweed
- Ragweed
- Knotweed
- Buttercup
- Shepherd's purse
What Killex Does NOT Kill
- Grass (by design)
- Crabgrass (it's a grassy weed, not broadleaf — see mesotrione herbicide)
- Nutsedge or sedges
Killex does not kill crabgrass. Crabgrass is a grassy weed, and Killex only works on broadleaf weeds. If crabgrass is your problem, you need a different product — see our mesotrione guide or our grassy weed guide.
How to Use Killex
Mix 6 ml of Killex per litre of water. One 1L bottle covers up to 800 square metres — enough for most home lawns.
Spray in the morning or evening when it's not too hot. Avoid the middle of the day — heat dries it out too fast before the weeds can soak it in. Don't spray if rain is coming within 6 hours, or you'll need to redo it.
You'll see the weeds starting to curl and yellow within 2 to 4 days. They'll be fully dead within about 2 weeks.
Killex — Pros
- Safe for lawn grass — spray the whole lawn
- Kills 50+ broadleaf weed species
- Highly cost-effective — 1L covers 800 sq m
- Kills roots, not just tops
- Fast visible results in 2–4 days
Killex — Cons
- Does not kill crabgrass or grassy weeds
- Needs 6 hours dry time after application
- Not safe around vegetable gardens
- Requires proper mixing — not ready-to-use
What Is Roundup?
Roundup is one of the most well-known weed killers in the world. The most popular version in Canada is Roundup Concentrate.
It gets into the plant through its leaves and travels all the way down to the roots. The whole plant dies — including deep, stubborn roots that are hard to pull by hand.
Unlike Killex, Roundup kills everything it touches. Grass, weeds, garden plants — anything green. If the spray lands on it, it will die.
What Roundup Kills
- Over 200 types of weeds and grasses
- Ground ivy, Canada thistle, nutsedge
- Poison ivy, bindweed, johnsongrass
- Virtually any green, growing plant
Where to Use Roundup
- Driveways and sidewalk cracks
- Gravel paths and walkways
- Fence lines and around foundations
- Garden bed preparation before replanting
- Lawn renovation — when killing everything to start fresh
Where NOT to Use Roundup
- On your lawn while grass is present — it will kill the grass
- Near vegetable gardens without extreme care
- Around trees, flowers, or shrubs you want to keep
How to Use It
Mix Roundup Super Concentrate at about 2.5 fl oz per gallon of water. It's safe from rain in just 30 minutes — much faster than Killex. You'll see weeds turning yellow and brown within 2 to 4 days, and they'll be fully dead within 1 to 2 weeks. Very old, deep-rooted weeds may need a second spray.
Roundup breaks down in the soil within a few weeks. So you can spray an area, wait two weeks for everything to die, clear it out, and then plant new grass or flowers. It won't stay in the ground and cause problems later.
Roundup — Pros
- Kills 200+ types of weeds and grasses
- Safe from rain in just 30 minutes
- Kills weeds all the way to the root
- Great for driveways, paths, and clearing areas
- You can replant in the same spot within weeks
Roundup — Cons
- Kills grass too — do not use on your lawn
- Kills any plant it touches
- Wind can carry the spray onto plants nearby
- Be careful near trees, flowers, and shrubs
Killex vs Roundup: Side-by-Side Comparison
| Feature | Killex | Roundup |
|---|---|---|
| Type | Selective | Non-selective |
| Kills grass? | No | Yes |
| Active ingredient | 2,4-D, Mecoprop-P, Dicamba | Glyphosate |
| Weeds controlled | 50+ broadleaf weeds | 200+ weeds and grasses |
| Use on lawns? | Yes | No |
| Rainfast | 6 hours | 30 minutes |
| Visible results | 2–4 days | 2–4 days |
| Full kill | Up to 2 weeks | 1–2 weeks |
| Best for | Lawn weed control | Driveways, paths, clearing areas |
When to Use Killex
Use Killex when you want to kill weeds in your lawn without hurting the grass.
Picture this: you look out at your lawn in May and half of it is dandelions. The grass is still there, just buried under a sea of yellow flowers. Spray Killex across the whole lawn, wait two weeks, and those dandelions will be gone. Your grass stays green and healthy.
Good Killex Situations
- Clover patches spreading through otherwise healthy grass
- Plantain growing along the edges of your lawn
- Creeping Charlie slowly taking over a shaded corner
- General spring or fall broadleaf weed control across the whole lawn
Spray Killex in spring when weeds are small and growing fast — that's when it works best. A second spray in early fall can take care of anything that came back over the summer. Skip it during very hot, dry weather — weeds that are struggling to survive won't soak up the spray properly.
When to Use Roundup
Use Roundup when you want to clear out everything in a spot — when you don't need to save any plants in that area.
Think about weeds growing through your driveway cracks. There's no grass to worry about there. Just spray Roundup directly on the weeds, and they'll die all the way to the root. That area stays clear.
Good Times to Use Roundup
- Killing weeds along a fence or around your foundation
- Clearing a garden bed before planting new flowers or vegetables
- Getting an area ready for new grass or paving
- Killing off a whole section of lawn to start fresh
- Tough weeds on hard surfaces that keep coming back
Don't spray Roundup on a windy day. The spray can drift onto nearby plants and kill them too. If you're working close to plants you want to keep, use a small brush to apply it instead of a sprayer.
Can You Use Both?
Yes — and a lot of homeowners do. They're not the same product, so there's no reason to pick just one.
Many people use Killex on the lawn through spring and summer to keep weeds out, and keep Roundup for the driveway, fence line, and any spots where they just want everything gone. Some also use Roundup in the fall to kill off a tired old lawn, then start fresh with new seed or sod the following spring — and switch back to Killex once the new grass is in.
Where to Buy Killex & Roundup in Canada
Both products are widely available across Canada in store and online. For homeowners in areas like King City and Caledon looking for fast delivery, Check price — Canada-wide shipping, typically delivered within a few business days.
If you're looking for an iron-based alternative that works across all of Canada, Fiesta Lawn Weed Killer and Scotts Weed B Gon MAX are excellent options available online — Check price.
If you're ordering online, buying two or three items at once brings down the shipping cost per item. And if it's your first time buying concentrate, add a sprayer to your order — it's much easier to use and you won't waste any product.
Price Comparison in Canada (2025/2026)
Prices vary by retailer and season, but as a general guide:
| Product | Size | Price Range | Coverage |
|---|---|---|---|
| Killex Concentrate | 1L | $46–$55 | Up to 800 sq metres |
| Roundup Concentrate | 1L | $55–$90 | Up to 1,000 sq metres |
When you mix both products to the right strength, the cost per square metre of lawn is actually very similar. The main thing to watch when ordering online is shipping — buying a few products together in one order saves a lot compared to ordering one at a time.
For online ordering with fast Canada-wide shipping, Find out more — Killex, Roundup, Weed B Gon MAX, and sprayers all in one order. Ships to all provinces.
If this is your first time buying concentrate, grab a sprayer at the same time. Trying to apply it without one is a hassle and you'll waste product. A decent sprayer is cheap and makes the whole job much easier.
Common Mistakes Canadian Homeowners Make
Using Roundup on the Lawn
This happens a lot. Someone hears that Roundup is powerful, sprays it on their weedy lawn, and ends up killing all the grass too. Roundup kills everything — including grass. Always use Killex for weed control on a lawn you want to keep.
Spraying Before Rain
Killex needs at least 6 hours on the leaves before rain hits. If it rains sooner, it gets washed off and you have to start again. Always check the weather before you spray. See our guide on how long to wait after using weed killer.
Using Killex on Crabgrass
Killex does not kill crabgrass. It only works on broadleaf weeds. If you have crabgrass, you need a different product — see our mesotrione guide for help.
Spraying in the Middle of the Day
When it's hot outside, the spray dries up before the weeds can take it in. Spray in the morning or evening when it's cooler for the best results.
Expecting One Spray to Do Everything
Some weeds — like creeping Charlie, Canada thistle, and ground ivy — have very deep roots. One spray often isn't enough. Give it 3 to 4 weeks and spray again if needed.
Not Having a Sprayer
A lot of people buy concentrate and then try to apply it without a proper sprayer. You end up with patchy results and wasted product. Pick up a sprayer at the same time — whether you're in Oakville, Richmond Hill, or anywhere else in Canada, Check price and get everything in one delivery.
Frequently Asked Questions
Killex is safe on most common lawn grasses — Kentucky Bluegrass, Perennial Ryegrass, Fine Fescue, and Tall Fescue. Do not use it on bentgrass or a lawn that was just seeded. Wait until your new lawn has been mowed at least 3 to 4 times before using Killex on it.
Keep kids and pets off the lawn until the spray has fully dried — usually 1 to 2 hours. Some people wait 24 hours just to be safe. Always check the label on the bottle for the most up-to-date advice.
Both are widely available across Canada in store and online. For fast delivery with Canada-wide shipping, Learn more — Killex, Roundup, and sprayers, delivered within a few business days.
Fiesta Lawn Weed Killer is one of the best options — it uses iron to kill weeds and is approved for use all across Canada. It's a popular choice for homeowners in Kleinburg and across the GTA. Scotts Weed B Gon MAX is also a good pick. Both kill dandelions, clover, and most common weeds without hurting your grass.
Roundup breaks down in the soil within a few weeks. After spraying, wait for everything to die (about 1 to 2 weeks), clear out the dead plants, and then you can seed. Wait at least 2 to 3 weeks after your last spray before putting down new seed — this gives your grass the best chance to grow.
Yes — Killex works well on both white and red clover. If you have a lot of clover, one spray might not get it all. Wait 3 to 4 weeks and spray again if needed, especially if the clover has been there for a while and has deep roots.
The Simple Answer
If your problem is weeds growing in your lawn and you want to keep your grass, use Killex. If your problem is weeds on a driveway, path, fence line, or an area you're clearing completely, use Roundup.
Neither product is better than the other across the board — they just do different things. Once you understand that difference, the choice is easy. Homeowners from Caledon to King City who have used the right product for the right job consistently see results within two weeks.
Spraying in May, when weeds are small and growing fast, will always work better than spraying the same product in August. Picking the right product matters — but so does picking the right time.
Both Killex and Roundup are available in store and online across Canada. Learn more and order both in one delivery to save on shipping.