Preen has a few statements on the label that may seem to contradict one another. First, you’ll notice that it claims to be safe to use on established plants. Then it goes on to say it’s not for use on lawns. But it’s also a pre-emergent herbicide so reason may suggest that established lawns would be just fine after an application of Preen. With all this conflicting information, it’s reasonable to still be wondering, “Does Preen kill grass?” In the article below, you should find your answer.
Does Preen Kill Grass?
Yes, Preen can kill grass in several different ways. However, Preen won’t always kill established grasses or lawns on contact. As a pre-emergent herbicide, Preen is more likely to slow growth, damage the nutrient absorption process, and kill any seeds before they get started.
What Will Preen Do to a Lawn
The primary ingredient of Preen is trifluralin. It is toxic to fish, frogs, all aquatic life, and all types of worms including earthworms. As such, Preen will deplete the populations of any or all of these to any area where it is applied.
Preen, when applied evenly to a plot of land, will create a layer of death for weed seeds and very early sprouts. Nothing will emerge and if it starts to, it will be killed upon making contact with this layer. If applied to a lawn, no seeds or sprouts will be able to emerge and bald patches may develop, depending on the grass type. Soil health may also degrade as Preen is not meant for application to contiguous areas.
Related Article: What Kills Grass? A Complete List of Dangers
Will Preen Prevent Grass From Growing?
No, Preen will not prevent grass from growing. However, the effects Preen has on grass will depend on its stage of development.
Does Preen Kill Grass Seeds?
Yes, Preen will kill grass seed. As a pre-emergent herbicide, Preen is designed to keep nearly any seed from germinating. This includes all types of grass seeds.
Does Preen Prevent Grass Recovery?
Preen should not affect the recovery of well-established plants. However, sprouts and small plants, and even the newly established blades of grass found on a rhizome may be damaged by Preen and experience slowed nutrient absorption.
Does Preen Kill New Grass or Sprouts?
New grass and sprouts may experience slowed nutrient uptake after being exposed to Preen. This may not kill them, but it could.
Will Preen Kill Grass of Any Type
Preen is an excellent pre-emergent herbicide, but it only works if there are seeds to kill. If a plant reproduces in a way that does not involve seeds, Preen isn’t particularly effective. Below are several common types of problem grasses and how effective Preen is at controlling or killing them.
Does Preen Kill Bermuda Grass?
No, Preen does not kill Bermuda grass. Bermuda grass spreads through stolons, also known as “runners”, and rhizomes. Bermuda grass can also produce and spread seeds, but this is only a secondary method of reproduction. Preen is, therefore, ineffective at preventing the growth of and killing Bermuda grass.
Does Preen Kill Crabgrass?
Yes, crabgrass is the single species of grass commonly considered to be a weed that Preen controls very well. Crabgrass does have a branching habit, but it spreads primarily via seeds, not rhizomes or a combination of the two. Once the major crabgrass plants have been removed, Preen can stop the seeds from growing and prevent reinfestation.
Does Preen Kill Johnsongrass?
Preen can help control the spread of Johnsongrass, but it is not a good method of control. Johnsongrass spreads via rhizomes every 2 to 3 weeks and by seed a few times a year. Preen can prevent these seeds from germinating but it does nothing for the rhizomes.
Does Preen Kill Quackgrass?
Like many troublesome types of grass, quackgrass (Elytrigia repens) reproduces primarily through rhizome production, with seed scattering a “backup” method. The only true way to reduce or get rid of quackgrass reliably is to pull it up and out. Preen, as a pre-emergent herbicide, is ineffective at reducing or removing quackgrass.
Does Preen Kill Nut Grass aka Nutsedge?
Preen does not kill any grown or active plants and will only kill plant seeds or spores. As nutsedge reproduces through nutlets and rhizomes as well as through seeds, Preen is relatively ineffective at preventing or controlling nutsedge.
Can You Save a Lawn After Applying Preen?
Preen is meant to be used at least 12” away from any “non-recommended” plant. This includes all lawns and lawn grasses. If Preen is accidentally sprayed on your lawn, the only and best option is to neutralize it with activated charcoal, also known as activated carbon, granules. This is not guaranteed to work and will be only partially effective if the Preen has already been watered into the lawn or soil.
Preen Can Prevent Grass from Growing
As it says in the fine print on nearly every preen label, Preen is not meant for use on lawns. Preen is a non-selective pre-emergent herbicide. It will prevent seeds of all kinds from germinating and can drastically slow sprout growth to the point where the plant may fail to thrive. Preen can also make it hard for plants to recover after injury or cutting, making it a sure-fire way to permanently damage your lawn if applied shortly before your lawn is mown.
