What chemical kills weeds?

When it comes to getting rid of weeds, using chemicals or herbicides is one of the most effective methods. Herbicides work by disrupting the normal growth processes of weeds, causing them to wither and die. There are many different types of chemical weed killers available, with different ingredients and modes of action. Choosing the right herbicide depends on factors like the type of weeds you need to control, whether the weeds are annuals or perennials, and where the weeds are located. Understanding the options can help you select the best weed killing chemical for your needs.

Common chemical weed killers

Some of the most popular and effective chemical weed control products include:

  • Glyphosate – Glyphosate is a non-selective, systemic herbicide that works by blocking the EPSPS enzyme pathway, which inhibits amino acid synthesis in plants. Glyphosate products like Roundup are effective on most types of weeds.
  • 2,4-D – 2,4-Dichlorophenoxyacetic acid (2,4-D) is a selective herbicide that mimics plant growth hormones. It controls broadleaf weeds like dandelions and clover but won’t harm grasses. Products with 2,4-D include Weed-B-Gon.
  • Dicamba – Dicamba is another systemic, selective herbicide for broadleaf weeds. It’s found in products like Banvel, Oracle, and Vanquish.
  • Pendimethalin – A pre-emergent herbicide that prevents germination and root growth of many annual weeds. Pendimethalin products like Pendulum AquaCap can provide residual weed control.
  • Trifluralin – Like pendimethalin, trifluralin provides residual control of annual grasses and broadleaf weeds as they germinate. It’s found in products like Treflan.
  • Glufosinate ammonium – An alternative to glyphosate in non-selective weed control products like Finale and Cheetah. It also inhibits amino acid synthesis in plants.
  • Imazapyr – Effective on woody brush as well as annual and perennial weeds, imazapyr (found in Arsenal) is absorbed and moves throughout the entire plant.

These are just some of the most widely used chemicals for killing weeds. Many herbicides combine multiple active ingredients to broaden the spectrum of weeds controlled. Always read herbicide labels carefully to ensure the product is suitable for your needs.

How do chemical weed killers work?

Herbicides control weeds through different mechanisms of action that interrupt critical plant growth processes:

  • Synthetic auxins – Synthetic auxin herbicides like 2,4-D and dicamba mimic the plant growth hormone auxin. They stimulate uncontrolled growth, causing the weed’s eventual death.
  • EPSP inhibitors – Glyphosate blocks the EPSP synthase enzyme pathway, shutting down amino acid synthesis required for plant growth.
  • Photosystem II inhibitors – These chemicals like atrazine disrupt photosynthesis, preventing food production in the weed.
  • ALS inhibitors – Acetolactate synthase (ALS) inhibitors like imazapyr block amino acid synthesis, leading to plant death.
  • PPO inhibitors – Chemicals that inhibit protoporphyrinogen oxidase (PPO), such as carfentrazone-ethyl, disrupt chlorophyll production and membrane integrity.
  • Seedling growth inhibitors – Pre-emergent herbicides like pendimethalin stop weeds as they sprout and emerge.

Understanding how an herbicide works can provide insight into what weeds it will effectively control. Weed resistance is also less likely to develop when herbicides with different modes of action are rotated.

Considerations when choosing a chemical weed killer

With all the chemical weed control options available, it helps to consider a few key factors when deciding which is best for your needs:

  • Weeds to be controlled – Match the herbicide to the weed species and life cycle (annual, perennial, woody). Certain chemicals are selective and only effective on grasses or broadleaf weeds.
  • Timing of application – Apply pre-emergent herbicides before weeds sprout. Use post-emergent products when weeds are actively growing.
  • Location – Only use non-selective herbicides like glyphosate where bare ground is desired. Use selective herbicides around desirable vegetation.
  • Residual activity – Pre-emergent herbicides have longer soil residual to continue controlling weeds over time.
  • Rainfastness – Some chemicals require a dry period after application before rain can wash them off plant foliage.
  • Leaching potential – Mobility affects how deep into the soil profile an herbicide moves to reach weed roots.

Also follow all label instructions carefully regarding proper spray equipment, dosages, timing, and anything else required for most effective and responsible use.

Common types of weeds controlled by chemical herbicides

Different herbicide active ingredients, formulations, and modes of action determine which weed types can be controlled. Some of the most problematic weed groups effectively managed with chemical weed killers include:

Annual grasses

Fast-growing annual grass weeds like crabgrass, foxtails, and annual bluegrass are commonly treated with pre-emergent herbicides to stop them as they sprout. Products with active ingredients like prodiamine, pendimethalin, dithiopyr, or benefin provide residual control of annual grass weeds in lawns, ornamental plantings, and gardens.

Broadleaf weeds

Several synthetic auxin herbicides selectively control broadleaf weeds like dandelions, plantain, purslane, and clover in turfgrass. 2,4-D, MCPP, dicamba, and triclopyr target broadleaves while leaving most grass species unharmed when applied at the right growth stage and dosage.

Vines and brambles

Fast-growing perennial vines and brambles like poison ivy, kudzu, and blackberry can overtake areas quickly. Systemic herbicides like glyphosate, triclopyr, and imazapyr that move throughout the entire plant are effective for controlling stubborn climbing vines and woody brush.

Aquatic weeds

Aquatic herbicides containing active ingredients like glyphosate, diquat, endothall, fluridone, or flumioxazin can manage underwater weeds like Eurasian watermilfoil, hydrilla, and duckweed in ponds, lakes, and canals when applied correctly.

Woody brush and trees

Unwanted woody vegetation like invasive trees and shrubs are difficult to control but can be effectively managed with systemic herbicides. Glyphosate, imazapyr, triclopyr, 2,4-D combinations in brush killers move down to the roots to kill the entire plant.

While chemical weed control products provide a fast and effective solution for many weed problems, they aren’t necessarily the best option for every situation. Integrated weed management using multiple methods is often the most sustainable long-term approach.

Organic vs. chemical weed control

In addition to synthetic herbicides, there are also organic weed control options. Some pros and cons of organic vs. chemical weed killing include:

Organic Weed Control Chemical Weed Control
  • Lower toxicity risks
  • Safer for beneficial insects
  • Prevents weed resistance
  • Repeated applications often needed
  • Slow speed of control
  • Less effective against perennials
  • Fast-acting weed control
  • Effective on all weed types
  • Simple and convenient to apply
  • Higher toxicity if misused
  • Can harm non-target plants
  • Resistance concerns with overuse

There are advantages and disadvantages to both approaches. Using organic techniques like mulching, hand weeding, smothering, or vinegar-based herbicides can reduce reliance on chemicals. But synthetic herbicides provide the speed and effectiveness needed in some weed control situations.

Most common herbicide ingredients

Some of the active ingredients most widely included in chemical weed killing products include:


Glyphosate is a non-selective, systemic herbicide that inhibits amino acid synthesis in plants. It is the world’s most widely used herbicide active ingredient, found in many products for farm, industrial, turf, aquatic, and residential weed control.


2,4-Dichlorophenoxyacetic acid (2,4-D) is a selective, systemic herbicide in the synthetic auxin class used to control many broadleaf weeds. It is included in weed killers formulated for lawn and turfgrass sites.


Dicamba is another systemic, synthetic auxin herbicide for selective broadleaf weed control. It may be combined with 2,4-D or glyphosate for a broader spectrum of control.


Imazapyr is a non-selective herbicide that inhibits the ALS enzyme for controlling a broad range of weeds, brush, and woody plants. It is the primary active ingredient in the product Arsenal.


Pendimethalin is a common pre-emergent herbicide for controlling annual grasses and some small-seeded broadleaves. It is found in various lawn, garden, and agricultural products.


Another systemic, synthetic auxin herbicide, triclopyr selectively controls broadleaf weeds and woody brush species. It is included in products like Garlon and Turflon Ester.

These are just a few examples of popular herbicide active ingredients that provide effective chemical weed control across many different land and aquatic sites when applied properly according to label directions.

Most common brand name chemical weed killers

Some of the most widely recognized brand name chemical weed killers include:


Roundup is a non-selective, systemic herbicide with glyphosate as the active ingredient. Its effectiveness on most weeds made Roundup the top selling retail herbicide.


Preen Weed Preventers contain the pre-emergent herbicide trifluralin to control annual grasses and broadleaf weeds. Preen products are commonly used in flower and vegetable gardens.


Spectracide makes a variety of general and selective weed killers containing active ingredients like diquat, 2,4-D, MCPP, dicamba, and glyphosate for lawn, garden, and agricultural uses.


Ortho is a brand of herbicide products for lawn and garden weeds sold under the company name ScottsMiracle-Gro. Ortho weed killers contain ingredients like 2,4-D, MCPP, dicamba, and glyphosate.


Compare-N-Save concentrates contain the active ingredients glyphosate, 2,4-D or 2,4-D and dicamba for lawn and garden weed control at a low cost.

These popular brand name weed killers represent just a fraction of the chemical herbicide products available to consumers, farms, commercial applicators, and public agencies.

Most common agricultural herbicide uses

On commercial farms and agricultural lands, herbicides are essential for maximizing crop yields and controlling costly weeds. Some major agricultural uses of chemical weed killers include:

  • Pre-plant burndown of emerged weeds before crops sprout
  • Pre-emergent application of residual herbicides to block weed seed germination
  • Post-emergent weed control in glyphosate-resistant corn, soybeans, cotton
  • Broadleaf weed control in cereal grains like wheat and barley
  • Clearing irrigation ditches, canals, and channels of weeds
  • Managing weeds on pastures, rangeland, and forage crops
  • Pre-harvest herbicide applications to facilitate harvest
  • Controlling invasive weeds and herbicide-resistant species

Herbicides allow farmers to limit competition from weeds for water, nutrients, and sunlight so crops can maximize growth and production potential.

Most common residential herbicide uses

In home lawns, gardens, and landscapes, typical herbicide uses include:

  • Spot treatment of lawn weeds like dandelions, clover, and plantain
  • Selective broadleaf weed control in warm and cool season turfgrass
  • Pre-emergent control of annual grassy weeds like crabgrass in lawns
  • Vegetable garden weed control between crop rows
  • Around patios, walkways, and landscapes to keep areas weed-free
  • Driveway and sidewalk crack weed control
  • Poison ivy, poison oak, and invasive vine control

For homeowners, herbicides provide a fast and effective solution for managing weeds in valued lawn and landscape areas.

Most common commercial herbicide uses

On lands other than farms and residential areas, herbicides help control unwanted vegetation in locations like:

  • Roadsides, medians, rights-of-way
  • Parks, recreational areas, golf courses
  • Railroads, powerline corridors, pipelines
  • Fence rows, lumberyards, storage yards
  • Drainage ditches, irrigation canals, levees
  • Ponds, lakes, and other aquatic sites

Municipalities, businesses, utilities and other entities use herbicides for vegetation management on public and private lands.

Most common industrial weed control uses

Herbicides also provide vital vegetation control around areas like:

  • Airports, ports, storage terminals
  • Road and highway medians
  • Electrical substations and power plants
  • Construction sites
  • Oil and gas well pads, pipelines
  • Solar farms, wind turbine sites
  • Railways, fire breaks

Maintaining weed-free surfaces is critical for safe operation and fire prevention in industrial locations.


Chemical weed killers provide fast, effective control of problem weeds that can quickly invade areas. Understanding the different types of herbicides, their ingredients, and proper uses allows you to select the right product for a specific weed problem. Always follow label directions carefully when applying any herbicide. While synthetic chemicals offer convenience and reliable results, integrated approaches using multiple weed control techniques helps reduce over-reliance on herbicides and herbicide-resistant weeds.

Leave a Comment