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Should I spray weed killer before or after mowing the lawn?

Weeds are a nuisance in the lawn because they compete with other vegetation for soil nutrients and sunlight. Eliminating weeds from your lawn keeps it healthy. Weed killers are often used because they can quickly destroy all the unwanted plants from your lawn.

Weed killers are contact destroyers. They get absorbed into the unwanted plants when they come in contact with the leaves. They, therefore, need to get excellent contact with the surface of the weeds to work effectively.

Most gardeners keep wondering about the best time to use weed killer on the lawn. The truth is the lawn can be adversely affected or even dry out if weed killers are applied at the wrong time.

The general rule is to wait for some time after mowing to apply a weed killer and also to wait after applying a weed killer before mowing.

So, should you apply weed killer before or after mowing? The best time to apply a weed killer is before mowing. This allows it to be absorbed by the weeds easily.

You shouldn’t apply weed killer after mowing since grass blades are still open and will most likely absorb the chemicals.

Applying pre-emergent and post-emergent weed killers

Weed killers are of two types, and both must be applied correctly for optimal performance. How soon to mow after applying weed killer depends on the type you use.

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Pre-emergent weed killers prevent weeds from growing on your lawn. For this type of killer, mowing before applying it can help get as much of it to the soil as possible.

Post-emergent weed killers work through foliage absorption. If you mow your lawn before applying it, you reduce the contact surface, and less of it will be absorbed by the weeds. For the best results, apply this type of weed killer before mowing your lawn to the desired height.

Using weed killer before the next mowing

The reason why you need to wait for at least one week after applying weed killer to mow your lawn is to ensure that most of the chemical gets absorbed by the unwanted plants.

If you spray and mow immediately, you will be removing most of the weed killer, as well as the leaves of the weeds containing the killer. As a result, the chemical will not work effectively.

Using a weed killer soon after the last mowing

A mowed lawn always has open grass blades that need time to heal. Applying a weed killer soon after mowing can negatively affect the grass on your lawn.

If you spray the weeds at the time when the blades of the grass are still open, the grass will absorb the weed killer and may dry up. It is ideal to wait for a few days or one week before applying a weed killer.

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Also, if you decide to mow first, you may not have enough weed surface to apply the weed killer. It may also become difficult to spot the weeds. The best time to use a weed killer on the lawn, therefore, is before mowing. This way, you will have enough leaf surface to apply the chemical.

So, should I cut the weeds before spraying or spray before cutting? The most accepted answer to this question is that you should spray the lawn at least a week before or a week after lawn mowing.

Be sure to give the leaves time to suck up the weed killer and transport it to the roots of the weed so that it dries up.

If you are not sure how long to wait before mowing, check the label of the weed killer, as it may give you the minimum time you need between applying the chemical and mowing.

Best conditions for using weed killer on your lawn

Besides understanding whether spraying weeds before or after mowing is the right thing to do, there are various other conditions that you must consider to ensure more effective weed control.

Some of these are:

  • Use the killer when there is enough moisture in the soil. Doing so in drought conditions can harm your lawn.
  • Apply the weed killer on dry grass and when it is less likely to rain for at least six hours. However, granular killers need to be applied when the grass is damp to ensure that they stick on the leaves long enough to absorb the weeds.
  • During the summer season, it is best to apply the weed killer in the evening when the sun is less strong.
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For the best results, use weed killer only before mowing your lawn. You shouldn’t mow immediately after applying weed killer, either. Instead, let it rest for about a week for the chemicals to be absorbed by the unwanted plants.