Weeds can be incredibly frustrating to homeowners, and it seems like every year there are more new products that claim to kill them. There aren’t, however, many products that stop weeds from happening at all. But that’s actually what pre-emergents do. Pre-emergents are a particular class of weed-killer that stop weeds from germinating by forming a impenetrable chemical barrier on top of the soil.
The soil in your lawn is packed with seeds that will grow into weeds. For example, a single crabgrass plant can create as many as 150,000 seeds. Chickweed plants produce several thousand seeds each – however, the seeds can remain viable in the soil for decades! When used properly, pre-emergents can be extremely effective at keeping these kind of weeds under control.
If you’ve used a pre-emergent unsuccessfully, it may be because they’re designed to impact the beginning stage of a weed’s life. Pre-emergents have no effect on already germinated seeds. This means that the bushes and flowers in your landscaping will be unharmed. Unfortunately, it also means that if your weeds have already germinated, pre-emergents won’t kill them. This can be solved by applying pre-emergent herbicides at exactly the right time throughout the year.
There are other reasons that your weeds may have already germinated. They may be perennials, so the live plant already exists. Or be particularly resistant weeds that can grow back from stray pieces of root. The best solution for these are post-emergent herbicides.
Your weed seeds may have also germinated if you are applying too late in the spring or if temperatures have been unseasonably warm in your area. Most species of weeds germinate when the temperature of the soil is approximately 50 degrees Fahrenheit. The date for this will vary greatly depending on your geographic location. To avoid this problem, apply your pre-emergents early and be aware of any forecasts for unseasonable weather. Generally, late February or early March will provide you with optimal prevention.
You should also watch for disturbances in your yard. Digging, or other gardening work, and pet activity can disrupt the chemical barrier that pre-emergents create. Those “holes” can allow weeds to break through and germinate. No matter how careful you are, some of this will happen, especially if you have children or pets. Keep a post-emergent herbicide on hand for spot applications on already-visible weeds.
Finally, make sure your pre-emergents are applied appropriately! Purchase enough to cover the entire area of application. Having too little may prevent your barrier from working at all! Follow the directions given on the bottle exactly. Make sure your spreader is distributing your pre-emergent evenly. If it isn’t, the uneven coverage will result in a barrier full of holes.
Generally, pre-emergents need to be re-applied every three months although weather conditions, such as heavy rain, can necessitate more frequent applications. When properly applied, maintained, and supplemented, pre-emergents can become an excellent primary weed-killer for any garden or yard.
At Environmental Turf Management, keeping your yard looking its best is our mission. Contact us for help with your lawn weed control.