Weed Killer

Eliminate pesky weeds from your lawn and garden with weed killers and herbicides

Weed Killer

Weed killers are chemicals that kill plants or inhibit their normal growth. The best weed killer depends on what types of weeds you are trying to eradicate. Herbicides vary according to their effects -- some aim to kill weed seedlings while others kill weeds after they are up and growing. 

This guide highlights the different types of available weed killer, along with application recommendations.

Types

There are four basic characteristics that describe how all herbicides work: emergence, selectivity, persistence and translocation.

  • Emergence weed killers are either pre-emergence, which target germinating seedlings before they grow, or post-emergence, which work on weeds that have already started growing.
  • Apply pre-emergent two to three weeks before the weeds germinate and apply post-emergent to the leaves of the plant.
  • Selectivity weed killers are either selective, which kill weeds without damaging nearby plants, or non-selective, which generally kill all plants in the vicinity of application.
  • Here’s the difference: You’d use a selectivity herbicide to kill dandelions without damaging your lawn, and a non-selectivity herbicide to kill weeds growing in sidewalk cracks.
  • Persistence describes how long the herbicides remain active after application. Those that provide no lasting prevention of weed growth are called non-persistent. Those that kill everything and prevent regrowth are persistent.
  • Translocated herbicides work their way through the plant’s internal system to break it down, while contact herbicides kill plants on contact.

Application

Apply herbicides to perennial weeds late in the growing season (early fall) for maximum effectiveness. And don’t mow for two days before and two days after applying herbicide.

Always check the manufacturer’s instructions and use the recommended concentration for best results.

Characteristic Target Application and Considerations

Contact

  • External
  • Annual weeds
  • Kills only the areas touched by the herbicide
  • Causes plants to die quickly

Non-persistent

  • Elimination of weeds without lingering effects
  • Works quickly and then gets broken down by microorganisms or sunlight
  • Won't interfere with plans to replant or reseed

Non-selective

  • All weeds, grasses and actively growing plants in an area
  • Use to control weeds in areas where no
    vegetation is desired
  • Ideal for sidewalks, driveways, patios
  • Can be used to prepare your lawn for replanting

Persistent

  • Regrowth of weeds
  • Provides continuous protection against weeds
  • Length of prevention time varies from product to product

Post-emergent

  • Visible weeds
  • Mature plants
  • Provides continuous protection against weeds
  • Length of prevention time varies from product to product

Pre-emergent

  • Germinating seeds
  • Seedlings
  • Spray into the soil two to three weeks prior to germination
  • Apply in spring to control growth of annual weeds

Selective

  • Specific weed type or types
  • Kills weeds without harming surrounding
    vegetation
  • Ideal for treating lawns, crops or ornamental gardens

Translocated

  • Internal
  • Perennial weeds
  • Absorbs through the roots or leaves
  • Penetrates weed system including the root structure