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Lawn Full of Weeds? The Weed Killer That Spares Your Grass

Weeds take over where grass is thin. Pull and mow high to slow them, then use a selective killer that clears the weeds and leaves your lawn alone.

By Jamilur Rahman Updated November 5, 2026 · 6 min read

Time
1 hour
Cost
$20-$50
Difficulty
Easy
A thin lawn covered in yellow dandelions and clover with a push mower parked at the edge
In this guide
  1. Quick answer
  2. Free vs. permanent fix
  3. What you'll need
  4. Why it happens
  5. Try this first (free)
  6. When free fixes aren't enough
  7. Buy the fix
  8. Broadleaf or grassy? Pick the right product
  9. What to skip
  10. FAQ
  11. Related problems

Quick answer

To fix a lawn full of weeds, thicken the grass and remove the weeds in the same season. Mowing high and pulling help, but a selective weed killer is what clears broadleaf weeds like dandelion and clover without killing the lawn, as long as the label lists your grass type. Fall overseeding keeps them from coming back.

Free fix vs. permanent fix

Free fix · 1 hour, then every mow

Pull, mow high and water deeply

  • Pull dandelions after rain, taproot and all
  • Mow at 3 to 4 inches for cool-season grass
  • Water deeply once or twice a week, not a little every day
  • Leave the clippings on the lawn

How long it lasts: Slows weeds for a season. A thin lawn keeps letting new ones in, and pulled taproots often regrow from leftover root.

Most readers choose Permanent fix
Selective lawn weed killer for broadleaf weeds (illustration)
Illustration

A selective weed killer matched to your grass

Clover and other creeping weeds spread faster than you can pick them. A selective killer targets the weeds and leaves lawn grass alone, so you clear them without a bare yard behind. It does not thicken thin grass, so pair it with high mowing and fall seed.

What to get: Selective lawn weed killer for broadleaf weeds

How long it lasts: Visible results usually within one to two weeks. A thick lawn then keeps new weeds out, and you re-treat only as the label allows.

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As an Amazon Associate I earn from qualifying purchases.

What you'll need

  • Dandelion weeder (illustration)
    Illustration

    Dandelion weeder

    A forked tool that lifts the whole taproot

    Check price

  • Work gloves

    For pulling weeds and handling the spray

    You have it

  • Lawn mower

    Set to the highest height your grass type allows

    You have it
  • Our pick
    Selective lawn weed killer (illustration)
    Illustration

    Selective lawn weed killer

    Check the label for your grass type and the weeds you have

    Check price
  • Grass seed for overseeding (illustration)
    Illustration

    Grass seed for overseeding

    Fills thin spots so weeds have no room

    Check price

Why it happens

1

Thin, weak grass

Weeds sprout wherever light reaches bare soil. Compacted soil, shade and too little feeding thin a lawn until weeds fill the gaps.

2

Mowing too short

Cutting grass to 1 or 2 inches lets sunlight hit the soil, so weed seeds sprout. Taller grass shades them out.

3

Shallow, frequent watering

A short sprinkle every day keeps the surface damp, which suits crabgrass and other shallow-rooted weeds, while the grass roots stay shallow too.

4

Seeds already in the soil

Weed seed can wait for years. Any gap wakes it up, and crabgrass sprouts once the soil warms to about 55°F in spring.

Try this first (free)

Do these in order, starting with the simplest.

  1. Name your weeds

    Broadleaf weeds such as dandelion, clover and plantain have wide leaves. Crabgrass looks like grass. Most selective killers target broadleaf weeds, and crabgrass and nutsedge need their own products.

  2. Pull the big ones

    Tool used: Dandelion weeder

    After a rain, push the weeder in beside the plant and lift the whole taproot. Pull dandelions before they turn to white puffballs and spread seed.

    Dandelion weeder (illustration)
    Illustration

    Tool for this step

    Dandelion weeder · A forked tool that lifts the whole taproot

    Check price on Amazon

  3. Raise the mower

    Tool used: Lawn mower

    Mow cool-season grass such as fescue and bluegrass at 3 to 4 inches, and never remove more than a third at once. Warm-season grasses are cut lower, so check your type.

  4. Water deeply, less often

    Give the lawn about an inch a week, rain included, in one or two soakings early in the morning. Deep roots help grass beat weeds.

  5. Treat the rest with a selective killer

    Tool used: Selective lawn weed killer

    Spray when weeds are growing, on a calm day, usually between about 60 and 85°F. Follow the label for rain-free time, mowing before and after, and how long to keep pets and kids off. Keep it off garden plants and trees.

    Selective lawn weed killer (illustration)
    Illustration

    Tool for this step

    Selective lawn weed killer · Check the label for your grass type and the weeds you have

    Check price on Amazon

  6. Overseed in fall

    Tool used: Grass seed for overseeding

    Spread seed over thin spots after mowing and keep it damp. Check the weed killer label for how many weeks to wait first.

    Grass seed for overseeding (illustration)
    Illustration

    Tool for this step

    Grass seed for overseeding · Fills thin spots so weeds have no room

    Check price on Amazon

When free fixes aren't enough

If weeds cover more than a quarter of the lawn, or the same ones keep returning, hand pulling cannot keep up. Creeping weeds like clover and ground ivy spread from runners, and pulling leaves pieces behind. That is when a selective killer saves hours. Read the label for your grass: St. Augustine and centipede lawns, for example, are sensitive to some active ingredients. If the lawn is more weed than grass, ask your extension office whether to renovate it.

Buy the fix

Still stuck after the free fixes? These are the products we would look at.

Our picks compared
PickProductFixesWho it's forBuy
Best pick
Selective lawn weed killer for broadleaf weeds (illustration)
Illustration
Selective lawn weed killer for broadleaf weeds
broadleaf weeds you cannot keep up with by hand Anyone with weeds spread across more than a few spots. Check price
Budget pick
Stand-up dandelion and weed puller (illustration)
Illustration
Stand-up dandelion and weed puller
scattered taproot weeds with no chemicals Lawns with a few dozen weeds, or anyone who prefers no spray. Check price
Upgrade pick
Grass seed for overseeding thin lawns (illustration)
Illustration
Grass seed for overseeding thin lawns
the thin grass that lets weeds in Anyone with thin patches who can seed in early fall. Check price
Best pick
Selective lawn weed killer for broadleaf weeds (illustration)
Illustration

Selective lawn weed killer for broadleaf weeds

Fixes: broadleaf weeds you cannot keep up with by hand

Look for: Label lists your grass type as safe; Lists the weeds you have, such as dandelion, clover and plantain; Clear rain-free time and re-treat interval; A hose-end or ready-to-spray bottle sized for your lawn.

Who it's for
Anyone with weeds spread across more than a few spots.
Honest downside
Your weeds are mostly crabgrass or other grassy weeds, which a broadleaf product will not touch. Also skip it on a lawn seeded in the last few weeks unless the label says it is safe.
Check price on Amazon
Budget pick
Stand-up dandelion and weed puller (illustration)
Illustration

Stand-up dandelion and weed puller

Fixes: scattered taproot weeds with no chemicals

Look for: A long handle so you can pull standing; A forked tip that gets under the taproot; A foot plate for leverage.

Who it's for
Lawns with a few dozen weeds, or anyone who prefers no spray.
Honest downside
Your weeds spread by runners, like clover and creeping Charlie. Pulling leaves pieces that regrow.
Check price on Amazon
Upgrade pick
Grass seed for overseeding thin lawns (illustration)
Illustration

Grass seed for overseeding thin lawns

Fixes: the thin grass that lets weeds in

Look for: A blend named for your region and sun level; Fresh seed with a recent test date; Coverage stated for overseeding.

Who it's for
Anyone with thin patches who can seed in early fall.
Honest downside
You just used a weed killer or crabgrass preventer. Many block new seed, so check the label wait time first.
Check price on Amazon

As an Amazon Associate I earn from qualifying purchases. We don't show prices because they change, so use the button to see today's price.

How we picked: How we picked: this page is based on lawn care guides from university extension offices, selective herbicide labels and the problems and fixes owners report in reviews. We do not test products by hand.

Broadleaf or grassy? Pick the right product

  • Dandelion, clover, plantain: a selective broadleaf killer.
  • Crabgrass: a preventer in early spring, before soil reaches about 55°F, or a killer labeled for crabgrass in lawns.
  • Nutsedge: a product that lists sedge. Regular broadleaf killers will not do it.

What to skip

Vinegar and salt on the lawn

Both burn grass as well as weeds and leave bare patches. Salt also harms the soil, so new grass struggles to grow there. Use a selective product made for lawns instead.

Frequently asked questions

How to fix a lawn?
Fix it in order: find the cause, mow high, water deeply, feed in fall, overseed thin spots, then deal with weeds. A thick lawn is the best long-term weed control.
What is the best time to kill lawn weeds?
Spring and early fall, when weeds are actively growing and the weather is mild. Fall is especially good for perennials like dandelion, since they are storing food in their roots.
Can I seed and use weed killer at the same time?
Usually not. Many weed killers can harm new seedlings and some products block seed from sprouting. Follow the label wait time, or pull weeds by hand around new seed.
Is lawn weed killer safe for pets?
Follow the label. Most say to keep pets and children off until the spray has dried, and some give a longer wait.

As an Amazon Associate I earn from qualifying purchases. Affiliate disclosure

Selective lawn weed killer for broadleaf weeds (illustration)
Illustration

Our pick: Selective lawn weed killer for broadleaf weeds

Check price