What's in this guide
How to Identify Dandelions
Dandelions are one of the easiest weeds to identify — but it's worth confirming before you spray, since a few lookalikes (like cat's ear) require a slightly different approach.
Leaves: Deeply toothed, lance-shaped, in a ground-level rosette. No hair on the upper surface. Stem: Hollow, single, produces one yellow flower per stem. Exudes milky white sap when broken. Root: Single, deep taproot — often 6–18 inches deep in established plants. Seed head: Distinctive white "clock" globe. Spreads by wind-blown seeds.
The main lookalike is cat's ear (Hypochaeris radicata), which has hairy leaves and branching stems. It also responds to 2,4-D-based products, so the same treatment works. False dandelion (Agoseris) is less common and also broadleaf-herbicide susceptible.
Why Hand-Pulling Doesn't Permanently Work
Dandelions have a fleshy taproot that can extend 18 inches or more into the soil. Any piece of root left behind — even a 1-inch fragment — will regenerate a new plant. Studies show hand-pulling without a tool has only a 30% permanent eradication rate because the root almost always breaks.
This is why systemic herbicides are so effective: instead of trying to physically remove the root, the herbicide is absorbed through the leaves and transported all the way down to eliminate the root from within.
3 Methods: Which One Is Right for You?
2,4-D + MCPP + Dicamba blend. Absorbed through leaves, eliminates roots. 95% success rate. Selective — won't harm grass. Best for lawns with many dandelions. Requires 24–48 hr dry weather.
Fiesta (iron chelate / FeHEDTA). PMRA-approved for Ontario/Quebec. Eliminates top growth fast (hours), but root control is incomplete — may need repeat treatments. Best for restricted regions.
Use a dandelion fork or fishtail weeder — not bare hands. Wet soil first to loosen roots. Get the full root or it regrows. Best for a small number of dandelions in a well-established lawn.
Product Success Rates — Our Test Results
We tested five products on dandelions during our May 2025 field test in Brandon, Manitoba. Results measured at 14 days post-application.
| Product | Elimination Rate | Rating | Region |
|---|---|---|---|
| Killex Concentrate (Scotts Canada) | 🇨🇦 Canada | ||
| Weed B Gon Lawn Weed Killer | 🇨🇦🇺🇸 Both | ||
| Roundup for Lawns | 🇨🇦🇺🇸 Both | ||
| Fiesta (Iron-based, organic) | 🇨🇦 Ontario/QC | ||
| Manual removal (dandelion fork) | Any |
Treatment Timeline: What to Expect Day by Day
Herbicide being absorbed through leaf surfaces and moving into vascular tissue. Normal — be patient.
Auxin disruption is underway. The plant's growth hormones are being overridden — the twisting means it's working.
Chlorophyll production is failing. The plant can no longer photosynthesize. Leaves turn pale yellow.
Above-ground growth is dead or dying. Root elimination occurring simultaneously in well-absorbed applications.
Safe to remove. Wait 3–4 weeks before reseeding the bare spot to ensure residual herbicide has cleared.
How to Apply — Step by Step
Don't mow for 3–4 days before applying. You need maximum leaf surface area for the herbicide to absorb. Freshly mowed dandelions have less foliage to take up the product.
Check the forecast. You need at least 24–48 hours without rain after application. Apply when temps are 60–85°F. Avoid applications during heat waves above 85°F or during drought stress.
Mix at the correct rate. For Killex: 6 ml per litre of water. For Weed B Gon RTU: use as-is. Always measure — under-dosing is the most common reason treatments fail.
Apply to wet foliage on a calm morning. Spray until foliage is wet but not dripping. Avoid windy days — drift onto garden beds will damage flowers and vegetables.
Don't mow for 3–4 days after applying. The herbicide needs time to move from the leaves into the root system. Mowing too soon removes the treated foliage before full absorption.
Wait and assess at 14 days. If 20% or more of dandelions are still showing green growth, a second application is appropriate. Allow 30 days between treatments.
In fall, dandelions are moving energy from leaves down to the taproot for winter storage. A systemic herbicide applied in September–October hitches a ride with that energy transport — meaning deeper, more thorough root elimination than spring applications on mature plants.
Best Time to Apply by Season
Late spring (May–early June) is the #1 window. Young dandelions in the rosette stage haven't built a deep root system yet, and they're actively growing — meaning faster absorption and the best results. Target the period just before or just after the first flowering for maximum results.
Fall (September–October) is the best window for large, established dandelions. The herbicide follows the plant's own energy-transport system deep into the root. This is the approach recommended for lawns with persistent, multi-year dandelions that regrow after spring treatment.
Summer treatments work but are less effective — heat causes rapid evaporation of the herbicide before full absorption, and both grass and weeds may be stressed. If you must treat in summer, apply at 7–10 AM or after 5 PM, never midday.
How to Stop Dandelions from Coming Back
Dandelions are opportunistic — they colonize weak, thin areas of lawn. A dense, well-fed lawn is the best long-term prevention.
What Prevents Dandelions
- Mow at 3–3.5 inches height — taller grass shades out seedlings
- Overseed bare spots immediately after removing weeds
- Fertilize in fall to strengthen grass root systems
- Aerate compacted soil to encourage thick grass growth
- Water deeply but infrequently (promotes deep grass roots)
- Annual spot treatment each spring catches new seedlings early
What Makes Them Worse
- Scalping the lawn (mowing too short) — opens gaps for seeds
- Leaving bare patches after removing dead weeds
- Under-fertilizing — weak grass can't compete
- Allowing dandelions to flower and seed before treating
- Treating in winter when plants are dormant
- Using contact-only products that don't reach the roots
A single dandelion clock can disperse 150–200 seeds, each capable of travelling hundreds of metres in the wind. If you see white seed heads, remove them by hand before spraying — this prevents re-seeding while you wait for the herbicide to work.
Frequently Asked Questions
Final Verdict
Dandelions respond extremely well to systemic broadleaf herbicides — 95% success rate in our tests with Killex and Weed B Gon. Apply in late spring before flowering, don't mow for 3 days before or after, and reseed bare spots. For Ontario/Quebec, Fiesta gives 72% results without violating the cosmetic pesticide ban.
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