Even the most vigilant gardener will have a weed or two in their lawn. Herbicides are useful in the battle against annual, perennial, and biennial weeds, but you have to know when to use them and which ones are most effective against a particular weed problem. Pre-emergence weed killers are used on established lawns as part of an annual effort to combat plant pests. What are pre-emergent herbicides? These chemical compositions are used before weeds take hold to kill off infant root systems and keep them from growing. Learn how pre-emergent herbicides work so you can decide if they are the right method for you.
Pre-emergence weed killers are used before you see the weeds to prevent them from showing up in the garden or lawn. This doesn’t mean the chemicals interfere with germination but rather they stop the formation of new root cells in baby weed plants. Without weeds, the seedlings cannot continue to feed and grow and they just die back. This whole process happens at the soil level under the blades and thatch of the grass so you don’t ever have to see the sprouted weeds. Timing, weather, and the type of weeds that are problematic in the garden will dictate the exact formula and application for using pre-emergents.
Types of Pre Emergent Herbicide
Pre-Emergent Info for Applications As with most plant chemicals, the weather and type of weeds will affect the application method. When using pre-emergents for winter annuals, apply in fall because that is when the seeds germinate. Summer annuals germinate in spring and that is the correct time to apply a pre-emergent. If you are unsure what type of weed is the most troublesome, it is a safe bet that a springtime application will control the majority of the pests. Pre-emergent weed killers require water to activate them and carry the chemical down to the root systems of newly sprouted weeds. Never apply an herbicide spray when there is a wind to prevent injury to other plants. The ambient temperature must be above freezing and the soil should be workable. Consult the manufacturer’s label for the varieties of weeds the product is effective against and the method and timing of application.
How Pre-Emergent Herbicide Works
To get a better idea of how pre-emergent works, let’s look at 3 key principles of pre-emergent weed control.
1: Pre-emergent herbicides are designed to control germinating weed seeds.
As its name suggests, pre-emergent is targeted towards weeds that have not yet emerged from the soil. To get the best results and to avoid wasting time and labor cost down the road, the weeds shouldn’t be visible above ground at the time of application.
Important: Pre-emergent is not designed to control existing weeds or weed seeds.
The weed will only be killed when it begins to sprout from the seed and hits the herbicide barrier. It is possible for seeds to remain dormant and not be harmed by the pre-emergent herbicide application. This is why weed control is a constant process. There will always be seeds under the surface and a portion will germinate each season. Annual applications must be made to significantly reduce large infestations.
Remember, pre-emergent herbicide can affect desirable plants. That includes turf. Caution must be taken if you’re applying pre-emergent and seeding the turf in the same season. Seed first, then apply pre-emergent at least 6 weeks later to allow for lawn establishment. Or seed at least 3 months after the pre-emergent has been applied.
2: Pre-emergent must be mixed correctly and applied evenly over the target area for best results.
Pre-emergent herbicides need to be mixed correctly for the spray solution to be at the appropriate strength. Take the time to read the manufacturer’s recommendations and don’t forget to calibrate your sprayer!
Thorough coverage is key. Think of pre-emergents like a blanket – you need to cover an entire area through which the weed seeds cannot germinate. Spot spraying achieves nothing, as there is plenty of open space for weeds to come through. Manufacturer instructions will indicate how much product to use “per 1000 square feet” or “per acre”, which determines how much herbicide to use for each gallon of water. Note that it usually takes 1 to 2 gallons of spray solution to cover 1000 square feet.
3: Pre-emergent herbicide must be watered in.
Watering in activates the herbicide, creating a barrier just below the surface. Most products call for 0.5 inches of irrigation or rain within 21 days after application.
Benefits of Pre-Emergent Weed Killer
Pre-emergent weed killers are a homeowner’s best friend. First and foremost, these herbicides eliminate the pesky plants before they become a problem. They also greatly reduce time spent pulling weeds by hand or spot-treating existing weeds.
Proactive weed elimination pays dividends. When weeds are left to grow and mature, they produce more seeds which equate to more weeds in the future. Since pre-emergent weed killers prevent seed production altogether, Charlotte homeowners save money and time for seasons to come.
Prices of Pre Emergent Herbicide
$14.55 – $94.95