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What is pre emergent, and how does it help my lawn?

What is pre emergent, and how does it help my lawn?

Updated: Aug 1, 2023


What is pre emergent, and how does it help my lawn?


Pre emergent herbicides are products applied to the soil before specific weeds have germinated. Once applied rain and irrigation settles the product into the soil forming a weed preventing barrier.


When the target weed seed germinates, it comes into contact with this pre emergent layer. When the root or leaf of the seed contacts this barrier it kills the intended weed. This process happens while the weed is small and concealed below the canopy of the turf.


Will pre emergent herbicides prevent all weeds?


Weed preventers have active ingredients that can prevent or lessen specific types of weeds. Unfortunately there isn’t a once size fits all solution that prevents all weeds and is safe for all turf types. It takes a lot of experience to know which product to use in each situation.


Its important to mention that many pre emergents mention what percentage of a specific weed they control. The pre emergent weed killer should stop most of the weeds listed on the label. Some however will still grow and need to be treated later with a post emergent herbicide.


When to apply pre emergent.


Depending on which weed needs prevented this might mean early spring pre emergent or late fall. It could mean mid summer or late winter pre emergent.


To prevent weed growth, pre emergent products should be used prior to the germination of weeds. If you already see crab grass growing for example, applying crabgrass preventers is not the answer. Application of pre emergent products should be done prior to weed germination.


The use of weed prevention products requires careful planning. When weed seeds germinate is greatly influenced by soil temperatures. For example, crab grass germinates at a different soil temperature than yellow nut sedge.


To know when to use pre emergents the applicator needs to know:

  • Which weed they specifically are trying to prevent.

  • They need to know at what soil temperature the weed will begin to germinate.

  • Know how long the herbicide works in the soil for specific weed prevention. It can change based on soil, rain, how soon the product is watered into the soil, and temperature.

  • When the soil will reach a temperature warm enough or low enough for the seed to germinate.

Keep in mind the soil temperature is different from the air temperature. Then the correct product must be applied according to the directions on the herbicide label.


How to select the best pre emergent.


Different herbicides have different active ingredients. Its important that a weed prevention product is safe for the turf its being sprayed on. A weed preventer that is safe to apply to bermuda might kill or injure st augustine.


Due to the different active ingredients it is important to ensure the product is labeled to prevent the target weed. The active ingredient of a weed control product that is a crabgrass pre emergent might have no effect on poa annua grass.


The product the weed control company will use will also be labeled for the location it is applied too. Weed preventers can be labeled for ornamentals, residential lawns, farms, sod farms, etc. The herbicide might also require a buffer zone of a certain distance from bodies of water, wells, water channels or crops.


Responsible safe use of herbicides protect people and the environment.


Do pre emergent herbicides work?


Applying pre emergent herbicides is a very effective element of weed control. While some weed seeds may break through this preventive layer it will greatly reduce the number that do so. The target weeds that do manage to germinate need to be treated with a post emergent. This will help prevent pre emergent resistant weed biotypes from spreading.


Can I spread grass seed after pre emergent is applied?


I typically suggest against doing so, however with careful planning it can be done. The pre emergent that prevents weeds seeds can also prevent the germination of grass seed.


Therefore it is important to consult with your weed control applicator before spreading any grass seed.


Often it requires timing the spreading of the seed between applications of pre emergent herbicide. The label on the product often states how long to wait to seed after the application of the product. It also frequently mentions how long to allow the grass to establish before re applying the product. The last thing anyone wants is to have freshly sown grass seed killed by a weed controlling product.


To fix thin grass, our lawn experts figure out the problem causing it and solve that instead. Once the turf is healthy it will out compete the surrounding weeds and quickly spread and fill in.


Are pre emergents safe for sod?


Much like grass seed, careful consideration must be given to to using weed preventers on freshly laid sod. Each specific product often provides direction regarding if and when their product is considered safe to apply to new sod.


What is the best method of weed prevention?


The best method of weed prevention is a dense thick growing turf. Weeds thrive in bare open places.


Pre emergents are a valuable tool for achieving a weed free lawn. However they should not be relied upon entirely. Herbicides aren’t a replacement for proper turf management.


Turf grass must be selected and maintained in a way that they can out compete weeds. This means proper mowing practices, soil aeration, soil ph, irrigation habits, and also pre emergent and post emergent herbicides.


Is granular or liquid pre emergent better?


A granular pre emergent is simply using a pellet as a means of distributing an active ingredient. Liquid pre emergents maintain a mixture in what is usually a liquid carrier. When it is time to apply pre, both are effective forms of spreading the active ingredient.


Weed control in Hot springs ,AR


A healthy weed free lawn is the result of a carefully designed turf management and weed control program. When its time to apply selective herbicides trust a licensed professional.


Advance lawn care is available year round to bring out the best in your property. Our lawn care technicians service hot springs, hot springs national park, piney, percy, royal, lake hamiltion, red oak, rockwell, pleasant hill and surrounding areas. Let us focus on managing the turf while you focus on time well spent with the family.

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