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Tips for When and How to Apply Weed Killer to Your Lawn

When planning to apply weed killer (granular or liquid) plan around a predicted rainfall or sprinkler application, and severe hot days or mowing schedule.

Weed killers are a contact killer, meaning they absorb the chemical through what comes in contact with the leaf surface and then translocates the chemical throughout the plant. Since weed killers are dependent on contact, it is very important to get good contact with the weed.

Granular weed killers should be applied when grass is damp and should not be watered for 48 hours after application. The dampness of the grass ensures the granular weed killer will "stick" to the leaf. Water applied too soon after application can wash off the weed killer from the surface of the weed before it can be absorbed.

To get good contact with the weed, don't mow the grass before applying weed killers. Mowing eliminates the weed's surface area and ultimately decreases the success of the weed killer. Plan to leave your grass uncut for two days after application and five days before.

During drought conditions or if you are having trouble getting adequate control, add spreader sticker which will increase absorption of the weed killer. During stress periods, plants tend to be more defensive and the addition of spreader sticker can be beneficial.

Applying weed killer is a five-step process:

  1. Don't mow the lawn before or after weed killer application
  2. Plan around rainfall, or sprinkler application
  3. Water lawn lightly before application or apply in early morning to take advantage of dew
  4. Don't water after treatment for two days
  5. Stay off lawn for one day

    Early application of weed killer should be done to ensure control next year.