What Kills Weeds Permanently?

Weeds are unwanted plants that seem to pop up everywhere in lawns and gardens. While weeding by hand works for a time, the best way to get rid of weeds for good is to use an effective herbicide. There are several options for killing weeds permanently, depending on the types of weeds plaguing your yard and your preferred method of application. By understanding the pros and cons of each approach, you can develop an integrated weed management plan to eradicate those persistent undesirables once and for all.

Pre-Emergent Herbicides

Pre-emergent herbicides are designed to prevent weed seeds from germinating. They form a barrier on the soil that blocks weed seedlings from breaking through the surface.

Applying pre-emergent herbicides can help reduce the number of weeds that even start growing in your yard. They are a useful preventative measure and work best when applied before the ground temperature reaches 55° F, which is usually early spring and fall. This blocks the first flushes of annual weeds like crabgrass and foxtail.

Some popular pre-emergent herbicides are:

  • Pendimethalin – Controls annual grasses and some broadleaf weeds. Brand names include Pendulum, Prowl, and Halts.
  • Prodiamine – Also prevents annual grasses and some broadleaf weeds. Sold as Barricade and Pendulum Pro.
  • Dithiopyr – The active ingredient in Dimension herbicide that stops crabgrass and other annual weeds.
  • Corn gluten meal – An organic pre-emergent made from corn. May need frequent reapplication.

When using pre-emergents, proper timing is crucial for the best results. They will not kill existing weeds but do offer residual control for up to 3 months on average. It’s recommended to reapply at least once or twice per year. Granular forms are easier to spread evenly than liquid.

Non-Selective Systemic Herbicides

Non-selective herbicides will kill any plant they come in contact with. While risky around desirable plants, they can effectively control weeds in areas like driveways and bare soil. Systemic herbicides are absorbed into the plant and translocated throughout, killing the entire weed including the roots.

Glyphosate (Roundup)

The most widely recognized systemic herbicide, glyphosate is highly effective at killing established weedy growth. Sold under brand names like Roundup, KleenUp, and Honcho, it can be sprayed over unwanted vegetation or applied directly to individual weeds. Perennial plants like deep-rooted grasses and creeping Charlie may require repeat applications for total elimination.

Glyphosate has no soil residual activity, meaning new weeds can germinate after application. It is inactivated upon contact with soil and has low toxicity for people and pets when dry. Glyphosate will not harm nearby grass or ornamentals as long as it is not sprayed directly on their foliage.


Another non-selective, foliar-applied herbicide, glufosinate-ammonium is the active ingredient in Finale and Cheetah. It can provide slightly faster weed control than glyphosate but may also require repeat applications on resilient weeds.

Pelargonic acid

Found in Scythe andother commercial products, pelargonic acid destroys plant tissue on contact but has no residual effects. It is effective for fast burndown of annual weeds and control of young seedlings. Repeat applications are necessary for continued weed prevention. Pelargonic acid can cause plant injury if accidentally sprayed on desirable foliage and should not be used around edibles.

Selective Post-Emergent Herbicides

Post-emergent herbicides target weeds that are already up and growing. Selective varieties are designed to kill specific weed types but leave surrounding grass and other plants unharmed. This makes them ideal for lawn care. Timing is less critical with post-emergents, but spraying smaller, younger weeds is most effective.


A widely used selective herbicide for lawn and turfgrass, the 2,4-D in Weed B Gon, Trimec, and other products kills broadleaf weeds without damaging grass. It is absorbed through the foliage and moves throughout the plant while breaking down cell walls. 2,4-D is effective on dandelions, plantain, clover, and many other broadleaf weeds, especially when applied before they flower and go to seed. It can take 7-14 days to see results.


Dicamba is another selective herbicide that controls broadleaf weeds but will not harm grass when used according to label guidelines. Sold as Banvel, Vanquish, and Scotts Turf Weed and Feed, it is useful for spot-spraying weeds in the lawn or doing blanket applications on grass pastures and rangeland infested with invasive broadleaf plants. It may cause injury to some trees and ornamental plants.


MCPP (mecoprop) works against broadleaf weeds like dandelions, clover, thistle, and chickweed in established lawns. Finds in products like Trimec Crabgrass Killer and Ortho Weed B Gon Max, MCPP shows visible effects within 3-7 days. It can be mixed with fertilizers for easy application. Repeat treatments may be necessary on mature weeds.


Quinclorac selectively controls grassy weeds in turfgrass without harming lawn grasses. It is highly effective against crabgrass as well as foxtail, barnyard grass, and other annual grassy invaders. Drive XLR8, Ortho Weed B Gon Crabgrass Killer, and Quinclorac 75 DF all contain quinclorac. Results are often seen within a week.


Dismiss turf herbicide contains the active ingredient sulfentrazone which provides selective broadleaf weed control in warm and cool-season grasses. It also suppresses yellow nutsedge and other sedges. Dismiss is absorbed through weed roots and foliage and moves throughout the plant. Visible effects take 7-14 days but can provide season-long control.

Total Vegetation Control

For areas where you want to eliminate all plant growth permanently, non-selective herbicides combined with a residual pre-emergent herbicide can provide total vegetation control. This might be desirable along fences, paths, driveways, and other places prone to weeds where no plants are wanted.

Glyphosate can be mixed with a pre-emergent like prodiamine to kill existing growth and prevent regrowth by creating a lethal combination that stopped weeds from returning for several months. Oust XP also combines non-selective burndown with residual control. For best results, reapply annually before peak weed season.

Organic Herbicides

If you wish to avoid synthetic chemicals, there are a few organic herbicides that can help manage weeds without such harsh toxicity. These include:

  • Vinegar (acetic acid) – High concentrations of horticultural vinegar kill plants on contact. Repeat often.
  • Corn gluten meal – Prevents seeds from germinating. Reapply every 2-4 weeks. May take years to deplete seed bank.
  • Citrus oil – D-limonene extract from citrus peels strips wax from weed leaf cuticles causing desiccation.
  • Soap-based herbicides – Fatty acids disrupt cell membranes. Brands include Safer and Natria.
  • Boiling water – Kills weeds instantly. Avoid planting areas.

While natural, organic herbicides often require more frequent applications and have mixed results depending on growing conditions and weed types. They may help reduce some weeds.

Choosing the Right Herbicide

With all the herbicide options on the market, it can be tricky determining which is best for your particular weed problem. Follow these tips for success:

  • Accurately identify problem weeds and understand their growth cycle. This will help you choose the appropriate herbicide and timing for application.
  • For lawns, use selective post-emergent broadleaf herbicides like 2,4-D or dicamba to avoid grass injury.
  • Spot treat individual weeds instead of blanket spraying when possible to avoid collateral damage.
  • Time pre-emergent application for early spring to block annual weeds. Reapply as directed.
  • Combine herbicides with different modes of action for the best results on tough perennials.
  • Always read and follow the label directions carefully for best product performance and to avoid potential issues.

Application Methods

Proper application technique improves herbicide effectiveness while reducing waste and preventing unintended plant damage:


Lawn sprayers, backpack sprayers, and handheld wand sprayers allow precise application. Use flat fan nozzles for uniform coverage. Don’t spray plants on windy days to avoid drift. Adjust settings to provide the ideal spray pattern.


Push and handheld rotary spreaders ensure granular pre-emergent herbicides and weed & feed products are dispersed evenly. Use edge guard to keep product off hardscapes. Calibrate regularly.

Ready-to-Use Products

Pre-mixed liquid herbicides in ready-to-use containers allow targeted treatment of individual weeds or spots with no mixing or equipment required.

Wipes and Gels

Wick applicators and adhesive gels permit direct herbicide transfer to weed leaves while reducing risks of unintended contact. Helpful for areas near ornamental plantings.

Liquid Spray and Refillable Containers

Concentrated herbicides must be mixed with water according to label rates before use. Refillable spray bottles or tanks provide cost savings over ready-to-use.

Proper personal protection equipment like gloves, long sleeves, pants, and eye protection should be used with any herbicide.

Timing of Application

Applying weed killers at the right time improves their effectiveness on target weeds:

  • Pre-emergents – Apply early spring before soil temperatures reach 55F to block annual weeds. Reapply per instructions.
  • Post-emergents – Spray weeds early when small for the best control. Established or maturing weeds are harder to kill.
  • Broadleaf herbicides – Spray when weeds are actively growing and younger for optimal absorption.
  • Winter and perennial weeds – Early fall application limits growth and weakens root systems going into winter. Repeat as needed.
  • Spot treatments – Treat individual weeds as they appear before they develop seed heads and spread.
  • Before rain or irrigation – Herbicides are more effective when plants are actively absorbing moisture.
  • Avoid hot, dry periods – Weeds are stressed and less likely to absorb herbicides when dormant. Irrigate first or wait for rain if possible.
  • Windy days – High winds increase drift risk leading to off-target application. Delay spraying until conditions improve.

Safety and the Environment

Always exercise caution when using herbicides:

  • Read and understand safety information before use. Follow all label precautions and application guidelines.
  • Wear proper personal protective equipment like gloves, long pants and sleeves, closed toe shoes, and protective eye wear.
  • Avoid breathing in spray mist or drift. Use an approved respirator if necessary.
  • Prevent pets and children from entering treatment area until herbicides are dry.
  • Triple rinse containers, use up product, and dispose of empty herbicides properly.
  • Avoid herbicide runoff into storm drains, surface water, or sensitive habitats. Do not treat around well heads.
  • Allow treated plants to dry before mowing to reduce herbicide transfer in clippings.
  • Select least toxic options suitable for the situation. Start small to assess results before wide scale use.

While herbicides can seem like an easy solution for eliminating weeds, they do contain chemicals that can cause unintended plant damage or injury if misused. Carefully weigh if their benefits outweigh the risks for your situation. Always opt for the least toxic controls suitable for your specific weeds and setting.

Integrated Weed Management

Combining multiple weed control techniques provides the best long-term suppression with less reliance on herbicides. Strategies include:

  • Promoting healthy grass by proper mowing, fertilization, irrigation, overseeding, and aerating to crowd out weeds.
  • Maintaining a thick layer of mulch in garden beds and tree rings to block light from reaching weeds.
  • Manual hand weeding and cultivation with tools like hoes, cultivators, and weed pullers to uproot plants.
  • Using corn gluten meal, soap-based herbicides, or vinegar as organic pre-emergents with some effect on seeds and seedlings.
  • Allowing grass to grow taller and mowing higher to shade and outcompete low growing weeds.
  • Planting native groundcovers, wildflowers, and grasses that inhibit weed establishment once established.
  • Setting mower blades high and leaving clippings to act as a natural fertilizer and mulch to improve turfgrass vigor.
  • Overseeding bare spots and areas damaged by weeds with site appropriate grass seed.
  • Adjusting sprinklers and irrigation schedules to provide uniform coverage without over saturating areas.
  • Applying pre-emergent herbicides in combination with selective post-emergent weed killers.
  • Solarizing weed-prone areas by covering them with plastic sheeting during hot, sunny weather to bake underlying growth.

By integrating multiple preventative and control tactics, you can keep weeds at bay for good. Always opt for the least toxic approaches first before resorting to herbicides.

Common Lawn and Garden Weeds

Knowing the types of weeds plaguing your yard is the first step in getting rid of them for good:


Dandelions have taproots that are difficult to pull and can re-grow from any leftover root bits. Use 2,4-D or dicamba for effective control. Digging manually when soil is moist also helps.


Annual crabgrass seeds germinate in spring. Applying pre-emergent herbicides prior to germination provides the best control for this aggressive grassy weed. Quinclorac is effective on young crabgrass post-emergence.

Creeping Charlie

The creeping stems of this perennial weed can quickly spread. Triclopyr is effective but should be applied repeatedly for total control. Use borax for organic suppression of growth. Manual digging also works if the entire root system can be removed.


This prolific annual weed flowers and sets seed multiple times per year. It grows low in turfgrass. Spot treat with 2,4-D or dicamba for broadleaf control. Pre-emergents also help prevent its germination.


Clovers are difficult to control with lawn herbicides but are beneficial for pollinators. High nitrogen fertilization encourages grass to outcompete clover. Otherwise 2,4-D or triclopyr provides fair suppression but not complete removal.


Nutsedge is a perennial sedge with grass-like foliage and a robust tuber system, making it harder to kill. Use sulfentrazone (Dismiss) or halosulfuron (Sedgehammer) for selective yellow nutsedge control in turf. Repeated glyphosate treatment also works.

Wild Violets

Though pretty, self-seeding violets can invade lawns. Triclopyr is effective against wild violets. Ensure proper mowing height, fertilization, watering, and overseeding to encourage thick turfgrass growth that crowds them out.


Broadleaf plantain’s wide oval leaves stick out in lawns. Products with dicamba or 2,4-D target plantain without harming grass. Combining herbicides provides the most effective plantain control in lawns.


Field bindweed exhibits aggressive vine growth that climbs and wraps other plants. Systemic herbicides like glyphosate and triclopyr provide fair control when repeatedly applied to new growth. Total eradication is very difficult.

Poison Ivy

Repeated glyphosate spraying kills above ground poion ivy vines but may not destroy the root system. Cut large vines close to ground first. Use protective clothing and avoid herbicide contact with skin.


Quackgrass fools homeowners with its attractive blade-like leaves, but it’s an aggressive perennial grass. Non-selective systemic herbicides provide the best opportunity for removal without tilling. Preventing seed heads limits spread.

Key Takeaways

  • Pre-emergent herbicides form a protective barrier to block weed seeds from germinating. Apply early spring and reapply per label instructions.
  • Non-selective herbicides kill all plant material. Use with caution around desirable plants. Systemic options like glyphosate translocate throughout the entire weed.
  • Selective herbicides only kill specific weeds while leaving grass and other plants unharmed. Timing, identification, and rotation improves performance.
  • Total vegetation control combines non-selective and residual herbicides for extended prevention in areas without desireable plants. Reapply annually.
  • Organic alternatives like vinegar, soap, and corn gluten meal offer limited control but are less toxic. Results vary widely.
  • Always read and follow herbicide labels carefully to maximize effectiveness while ensuring proper application to avoid damage or injury.

With a combination of smart timing, selective herbicides, and routine maintenance like mowing, fertilizing, and irrigation, you can kill existing weeds and keep new ones from invading permanently. An integrated approach provides the best defense against the never ending war against weeds. Be patient and persistent for optimum, lasting results.

Frequently Asked Questions

What is the strongest weed killer?

Glyphosate (Roundup) is considered the most powerful and effective consumer-grade herbicide, especially when combined with a residual pre-emergent. However, be very careful during application to avoid damage to non-target plants.

What kills weeds permanently?

No single herbicide