Weed control comes in a variety of methods and strategies, but prevention remains the most effective way to control weeds in Nebraska. Pre-emergent is a chemical form of weed control that operates exactly as its name suggests; it eradicates weed seedlings before they are even able to emerge in your yard. This article will explain what pre-emergent is, how it works, and why your lawn and gardens need it!
What Is Pre-Emergent?
Pre-emergent is a herbicide that gets applied indiscriminately across your entire yard. This form of herbicide differs from post-emergent weed control, which typically focuses on isolated areas where weeds are visibly growing. Pre-emergent contains certain chemicals that are effective at stopping the growth of weeds in the soil, and it comes in either a liquid or granular form, giving you a number of pre-emergent options when it comes to weed prevention for your yard.
Granular Pre-Emergent
This form of pre-emergent has become the more popular choice among residential property owners in recent years. The chemical granules are well suited to the needs of smaller yards, and application of granular pre-emergent is simple enough that you could apply it by hand. Though it does not need to be mixed like liquid forms, granular pre-emergent MUST be watered after it is applied in order to activate and spread the chemicals.
Liquid Pre-Emergent
Larger areas that need to be protected quickly will benefit most from a liquid pre-emergent. While this form of pre-emergent covers the most ground, it can be a bit more tricky to apply it properly. The solution in liquid pre-emergent must be mixed with water, and the spray nozzle used for distribution must be calibrated correctly. It is imperative that you always check the instructions on the label before applying liquid pre-emergent.
Prodiamine
This chemical is used to prevent both grassy weeds and broadleaf weed types, including the all-too-common crabgrass and dandelions, just to name a couple.
Oxyzalin
Traditionally, this chemical is used on crops, but residential yards can also benefit from the weed control it provides. Bindweed is commonly targeted by this chemical.
Dithiopyr
Most people find that this chemical is best used in the fight against common grassy weeds, but it is also highly effective against low-growing vining weeds.
How Do Pre-Emergents Work?
The strategy through which pre-emergents succeed is simple but highly effective. Pre-emergents do not directly attack weed seeds as they are germinating, but they do prevent the process of germination from extending through the soil surface. When applied, pre-emergent creates a protective barrier across the soil in your yard. Seedlings that are attempting to germinate under the soil will hit this barrier and cease growing/germinating.
After germination is stopped, the young seedling will either go into dormancy or it will die. Preventing new weeds from emerging also means you are preventing all those potential weeds from spreading hundreds of more seeds, making pre-emergent weed control a complete remedy.
For more information on how we use pre-emergent, check out our fertilization and weed control page!
When To Apply Pre-Emergent
- Spring - Summer annuals germinate in spring and wreak havoc all summer. To prevent these types of weeds, pre-emergent should be applied in early spring, typically sometime in March.
- Fall - Winter annuals germinate in fall and die in spring, but many will set seeds that go dormant in the soil over winter. Pre-emergent should be applied in late summer or early fall to prevent winter annuals (before mid-September).
- While Fertilizing - Pre-emergent herbicides are often blended together with fertilizers. Including pre-emergent in the mixture will help ensure that your desired turfgrass is able to grow freely and absorb the maximum amount of nutrition by way of eliminating weeds while your grass gets fertilized simultaneously.
- Before Weeds Are Visible - Pre-emergent is only effective on weeds that you can not yet see above the soil surface. Applying pre-emergent to visible weeds will not kill them, and it will likely not even harm the weeds. Getting to a baby seedling before it emerges is the best way to control it.
- After Grass Has Grown - No type of pre-emergent is able to differentiate between weed seeds and healthy grass seeds. For this reason, you should never apply pre-emergent directly before or after overseeding your lawn. Pre-emergent will prevent grass from emerging in the same way it prevents weeds. If you plan to lay down seed this fall, allow adequate time for grass to begin growing before applying pre-emergent.
Pre-Emergent FAQ
Are all pre-emergents also fertilizers?
Pre-emergent can be purchased and used separately from fertilizers. Many people prefer to utilize a two-in-once solution to save time, which is also an effective weed control option, but applications of fertilizer and pre-emergent do not have to be simultaneous.
Do pre-emergents work on perennials?
Pre-emergents are most effective against annual weeds because they will die out after only a year or so. Perennials can be much harder to control because of how frequently and quickly they set seeds and spread roots. However, consistent pre-emergent applications will at least weaken perennial weeds and make them more manageable.
How long do pre-emergents last?
You should expect your pre-emergent barrier to last between 3 and 5 months, with factors like foot traffic and rainfall affecting duration. For the longest results, make sure the ground temperature is near 55 degrees for summer weeds and 70 degrees for winter weeds, and limit activity on the lawn for the first few days after application.
How much pre-emergent do I need to apply?
When it comes to using the correct amount of pre-emergent, try to focus more on making sure that your entire lawn is covered rather than applying a certain amount of mixture. Complete coverage is the only way to ensure success, as weeds will find even the tiniest hole in your pre-emergent barrier through which they can invade. A good rule of thumb is that 1,000 square feet will typically need between 1 and 2 gallons of pre-emergent mixture.
Pre-emergent will need to be reapplied at the end of the 3-5 month period, and applications should continue every growing season. Seeds can be dormant in the soil for years, and some weeds can repopulate without even needing seeds to germinate. Thorough and repeated applications are the best way to keep weeds out of your lawn and gardens.
