When to Spray Dandelions

Updated September 2026 · Garden Advice Guide

Spray dandelions in fall, from mid-September through early November, once night temperatures have cooled but the plants are still green and growing. That single window kills 85 to 95 percent of a dandelion population, compared to roughly 50 to 70 percent for the same product applied in spring. Knowing when to spray dandelions matters more than which bottle you buy, because in fall the plant is actively pulling sugars down into its taproot and it carries the herbicide along for the ride.

If you can't wait until fall, the spring backup window is late April through May, at full bloom, on a calm day between 60 and 85°F.

Line the date up with the rest of your lawn jobs using our free lawn care schedule tool, because spray timing collides with seeding and fertilizing more often than people expect.

Updated September 2026

A note on numbers. This page gives you timing windows, air and soil temperatures, mixing rates and kill percentages, not dollar figures. Herbicide concentrate and weed and feed are priced by your region, your retailer and the season, and we do not set any of it. Work out your date and your rate here, then buy locally.

When to spray dandelions: fall beats spring, by a lot

A dandelion is a perennial with a taproot that can reach 10 to 15 inches down. The leaves you see are disposable. The root is the plant.

That's why spring spraying disappoints so many people. In April and May, a dandelion is pushing energy upward into leaves and flowers. Herbicide sprayed on those leaves moves with the plant's internal flow, and in spring that flow largely runs away from the root. You burn the top, the plant looks dead for two weeks, and a fresh rosette appears in June from a root that never got the message.

In fall the direction reverses. Once nights start cooling, the dandelion begins moving sugars downward to store them for winter. Anything on the leaves goes down with them, straight into the crown and the taproot. That's the difference between a plant that regrows and one that never comes back.

If you take one thing from this page: spray on a mild day in October rather than a nice weekend in April. Same effort, roughly 30 percent more dead dandelions.

The conditions that decide whether a spray works

Date gets you into the right month. These five rules decide whether the application actually does anything.

Temperature: 60 to 85°F air. Below 60°F the plant absorbs slowly and the herbicide sits on the leaf. Above 85°F the turf is stressed and volatile products (especially ester formulations of 2,4-D and dicamba) can vaporize and drift onto tomatoes, redbuds, and grapes 100 feet away. The sweet spot is 65 to 80°F.

Rain-free for 24 hours after. Most broadleaf herbicides need 6 to 8 hours on the leaf to be absorbed, and 24 hours is the safe margin. A downpour at hour four means you sprayed water.

No mowing 3 days before, 3 days after. Herbicide enters through leaves, so the plant needs leaf area to catch it. Mowing right before a spray removes the target, and mowing right after removes the treated tissue before it has moved anything downward.

Wind under 10 mph. Broadleaf herbicides do not distinguish between a dandelion and a rose. Spray in the calm of early morning or early evening, not in an afternoon breeze.

Wet leaves help, dripping leaves don't. Light morning dew is ideal, because the spray spreads and clings. A soaking wet lawn dilutes and runs off.

Which product, and what the timing does to that choice

Most homeowner "broadleaf weed killers" are three-way mixes, typically 2,4-D plus dicamba plus MCPP or triclopyr. Blending gives broader coverage than any one active ingredient.

Two practical notes. Amine formulations are safer than ester formulations in warm weather, because they do not vaporize as readily. And on southern lawns, particularly St. Augustine and centipede, the standard three-way mix can do more damage to the grass than to the weeds. Check the label for your specific grass type every time, since the label is the legal instruction and this page is not.

Spot spray, not blanket spray

A dandelion is a target you can see. Treating 6,000 square feet of lawn to kill 40 plants puts herbicide on 5,900 square feet that had nothing wrong with it.

Spot spraying uses roughly 90 percent less product, costs less, stresses the turf less, and works better, because a hand sprayer wets the whole rosette while a granular weed and feed drops a few particles near it.

Reach for a blanket application only when the lawn is genuinely 30 percent or more broadleaf weeds, at which point you're rebuilding turf, not spot-treating.

Our guide to how to get rid of weeds covers the non-chemical side, including how to actually dig a dandelion taproot out in one piece.

Worked example: a 6,000 square foot lawn in zone 6

Numbers from a typical suburban front and back yard.

The situation: 6,000 square feet of tall fescue with about 60 visible dandelions, scattered. First hard freeze around October 25. The owner also wants to overseed a thin patch and fertilize.

The problem to solve first: overseeding and broadleaf spraying fight each other. Most broadleaf herbicides require you to wait until new grass has been mowed three or four times, roughly 4 weeks, before spraying. And several require waiting 3 to 4 weeks after spraying before seeding.

The sequence that works:

The mixing math. A concentrate labeled at 1.5 fluid ounces per gallon, covering 500 square feet per gallon at broadcast rate. Spot spraying 60 dandelions uses maybe 1.5 gallons of finished spray total, not the 12 gallons a blanket application would need.

1.5 gallons × 1.5 fl oz per gallon = 2.25 fluid ounces of concentrate. A standard 32-ounce bottle of concentrate therefore holds enough for roughly fourteen treatments like this one, which means one bottle covers this lawn for years.

Compare that to a bag of weed and feed sized for 6,000 square feet, which costs more than the whole bottle of concentrate, gets used up in a single pass, applies herbicide everywhere including the 5,900 square feet with no dandelions in it, and puts fertilizer down on a date chosen by the herbicide label rather than by what the grass needs. Spot spraying is both the cheaper option and the better one, which is a rare combination.

What the results looked like: by October 25, symptoms on all treated plants (twisting, cupping, yellowing). Spring counts showed 5 survivors out of 60, about a 92 percent kill. The same lawn sprayed the previous April had 24 of 55 plants regrow by June, roughly 56 percent.

Two identical bottles. Two different dates. Thirty-six percentage points of difference.

What a working spray looks like, and how long it takes

Broadleaf herbicides are growth regulators. They do not burn the plant down, they make it grow itself to death, so the symptoms are strange and slow.

• Day 1 to 2: nothing visible. This is normal and it's where most people conclude it failed.
• Day 3 to 5: leaves twist, curl, and cup. Stems bend into hooks. The plant looks like a bad drawing of itself.
• Day 7 to 14: yellowing, then browning from the center out.
• Day 14 to 21: the rosette collapses. In fall, the root dies below ground where you can't see it.
• Week 3 or later: if green regrowth appears from the crown, the root survived. Re-treat, but not sooner than 14 days after the first application and never more than the label's annual maximum.

Cool fall weather slows all of this down. A late October spray at 58°F may take three weeks to show what a 75°F September spray shows in five days. Slower is not weaker: the uptake is still happening.

Spring spraying, when fall isn't an option

Sometimes the lawn is a sea of yellow in April and waiting six months is not realistic. Spring spraying does work, it just works less well.

Time it to full bloom, not to first flower. Late April through May in most of the country. At full bloom the plant has maximum leaf area to catch spray and is still actively moving material through its system.

Do not spray after the puffballs form. Once seed heads open, the plant is winding down and uptake drops. You also just spread the seed by walking through it.

Expect to re-treat. Plan on a second application 3 to 4 weeks later on survivors, then a proper fall spray to finish the job. Two spring applications plus one fall application usually clears a heavy infestation in one year.

Watch the seeding conflict. Spring is also when people want to seed thin lawns. You cannot do both. Broadleaf herbicide applied in spring pushes seeding to July, which does not work for cool-season grass. Our guide to when to plant grass seed explains why that trade usually goes in favor of seeding.

The timing conflicts that ruin good intentions

Four collisions cause most wasted applications.

New grass. Do not spray broadleaf herbicide on grass seeded less than 4 weeks ago, or that has not been mowed three or four times. Young seedlings take the same growth-regulator damage the weeds do. The fall overseeding calendar is in when to overseed lawn in fall.

Seeding after spraying. Most broadleaf labels require 3 to 4 weeks between application and seeding. If both jobs are on your fall list, seed first in late August, then spray in October.

Weed and feed. These force one date onto two jobs with different best dates. The best fertilizer date for cool-season grass is early September. The best dandelion date is October. Splitting them costs nothing and does both correctly. Rates and dates are in when to fertilize your lawn.

Summer. No broadleaf herbicide above 85°F, and none on a drought-stressed lawn. Dandelions are semi-dormant then anyway, so you get poor control plus turf injury. Wait for September.

Stopping the next crop

Killing the dandelions you have is half the job. Dandelion seed blows in from every neighbor and every roadside, and a single plant releases 2,000 to 15,000 seeds.

Mow at 3 to 4 inches. Taller turf shades the soil, and dandelion seed needs light to germinate. This is the single highest-return change most lawns can make.

Feed on schedule. A dense, well-fed stand of grass leaves no bare soil for seedlings to establish in.

Fall pre-emergent. An isoxaben-based product applied in early fall blocks germinating dandelion seed through winter and early spring. It does nothing to established plants, so it pairs with, rather than replaces, the October spray.

Fix the bare spots. Dandelions colonize thin, compacted, or bare ground. Core aeration plus overseeding removes the opportunity.

Deal with the top two inches by hand. For a handful of plants, a dandelion fork in moist soil beats any spray. Get the root below 2 inches or it regrows. Ten plants take ten minutes.

The complete month-by-month job list, including pre-emergent and aeration timing, lives in our lawn care schedule.

Frequently asked questions

What is the best time of year to kill dandelions?

Mid-September through early November, on a day between 60 and 85°F. In fall the plant moves sugars down into its taproot and carries the herbicide with them, which is why fall applications kill 85 to 95 percent of plants versus 50 to 70 percent in spring.

What temperature is too cold to spray dandelions?

Below about 55 to 60°F, uptake slows enough that results become unreliable, and near freezing the plant has effectively shut down. Triclopyr-containing products stay somewhat effective down to about 55°F, which makes them useful for late-season applications.

How long after spraying dandelions can I mow?

Wait at least 3 days. The herbicide has to be absorbed and then translocated into the crown and root, and cutting the treated leaves too soon removes the delivery system. Also avoid mowing for 3 days before spraying, so there's leaf area to spray.

Will rain wash away dandelion spray?

Rain within the first 6 hours will substantially reduce control, and most labels ask for a rain-free period of 6 to 24 hours. Check the forecast, then add a margin: a spray that has been on the plant a full day is generally safe from a shower.

How long does it take for dandelions to die after spraying?

Visible twisting and curling starts in 3 to 5 days, yellowing at 7 to 14 days, and full collapse at 2 to 3 weeks. Cool fall weather can double those timelines. Regrowth from the crown after 3 weeks means the root survived and needs a second application.

Can I spray dandelions after I overseed my lawn?

Not right away. Wait until the new grass has been mowed three or four times, roughly 4 weeks after germination. Broadleaf herbicide damages young grass seedlings the same way it damages weeds. Seed in late August and spray in October, in that order.

Do I need to spray the whole lawn or just the dandelions?

Just the dandelions, unless broadleaf weeds cover 30 percent or more of the lawn. Spot spraying with a hand sprayer uses about 90 percent less product, costs a fraction as much, and wets the whole rosette better than any granular product does.

Does vinegar kill dandelions?

It burns the leaves and nothing else. Acetic acid is a contact material, so it destroys the tissue it wets but never reaches a 12-inch taproot, and the plant regrows in two to three weeks. Household strength is usually too weak to do even that, and horticultural strengths are corrosive enough to injure skin and eyes.

The short version

The best time to spray dandelions is mid-September through early November, on a calm day between 60 and 85°F, with no rain for 24 hours and no mowing for 3 days on either side. That timing works because the plant is hauling everything down into its taproot for winter, herbicide included.

Spot spray instead of blanket spraying, seed first and spray second in fall, and mow at 3 to 4 inches so the next batch of seed has nowhere to land. Get the exact dates for your zone from our free lawn care schedule tool and the rest of the season's jobs from the lawn care schedule guide.