Understanding what you’re applying and how it works will help you determine the right time to begin your lawn care. First things first—lawn care isn’t a race. Just because your neighbor is the first to grab the spreader doesn’t mean they’ve won the battle. When you head to the garden center, you’ll see terms like “preventer,” “crabgrass,” and “pre-emergent.” But what do they really mean?
No matter what brand you choose, most first lawn applications contain two main ingredients: fertilizer (to encourage grass growth) and a pre-emergent herbicide. A herbicide is a chemical designed to kill plants, unlike an insecticide, which targets pests. A pre-emergent herbicide, however, works differently—it stops plants from growing before they even sprout. The word “pre-emergent” itself tells you this: “pre” means before, and “emergent” refers to sprouting.
How Does a Pre-Emergent Herbicide Work?
A pre-emergent herbicide prevents weed seeds from sprouting, either before or just as they begin to grow. In other words, the weed killer you apply early in the season is actually a weed preventer. It creates a barrier in your soil that blocks the growth of seeds. But you might be wondering, “I’ve used pre-emergents before and still had weeds in the summer. Why?”
Here’s the catch: Pre-emergents only block weeds from seeds. If a weed is coming from an established root (like dandelions, clover, or ground ivy), a pre-emergent won’t stop it. Weeds that come back from roots need a different type of herbicide. So, while pre-emergents are excellent at preventing weeds from seeds, they won’t tackle plants growing from roots.
Why Crabgrass?
The biggest target of a pre-emergent herbicide is crabgrass. However, crabgrass won’t germinate until the soil temperature reaches the mid-50s—much later than the air temperature. Think of how long it takes for a lake to warm up in the spring. Even if it’s a sunny day, that water’s still cold! Soil temperature behaves similarly, warming up slowly over time. Crabgrass usually doesn’t start to germinate until late April or May in our area, which means you have plenty of time to apply your preventer.
Timing Is Key
To effectively prevent crabgrass, apply your crabgrass preventer between late March and mid-April. Soil temperature, weather conditions, and other factors affect when weeds like crabgrass germinate, and these can vary each year and from lawn to lawn. Feel free to stop by or give us a call for advice on the best approach for your specific needs.
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