How Does Weed Killer Work? Is It Good For Your Lawn?

Last Updated on January 5, 2023

Today, there is a wide variety of weed killers in production, thanks to their growing demand. Many of us who have a lawn or garden find weed killers like Roundup highly beneficial and essential for weed control. That’s why it is no wonder that weedkillers are becoming more and more popular.

But how does weed killer work? What kinds of weed killers are there? Do weed killers kill all plants or just weeds? And, what should you expect if you use a weed killer on your lawn? Keep reading to learn the answers to these questions and more!

Weed Killer Basics Explained

Before we go into how a weed killer works, let’s take a look at the basics first to ensure that you have a clear grasp of what a weed killer is.

What Is Weed Killer?

There are several different kinds of weed killers, but for the most part, a weedkiller is a herbicide. Most weed killers are chemical-based, but many homemade recipe options exist. In addition, many commercial gardening weed killers, like Roundup, contain glyphosate, enabling weed control after spraying it on your garden and lawn.

A weedkiller is typically easy to use as long as you wear protective gear while handling it and read the label for specific instructions. Using a weedkiller is also less time-consuming than manually pulling out each weed that sprouts in your garden or lawn.

How Weed Killers Work

Different types of gardening weed killers work in slightly different ways. However, they all kill weeds by affecting plant growth in one way or another. Some weed killers act by preventing and damaging the formation and growth of the roots.

Other types of weed killers restrict the growth of healthy cells in the weed or all plant life depending on the specific variety. They also target particular enzymes that form fat. This effectively stops the development of new cells, and eventually, the roots and entire plant die.

While all weed killers are related somewhat, the type of weed killer you use will also determine its effectiveness and the kind of vegetation it kills. It will also vary when to use the weed killer for optimal results.

What Are the Most Common Types of Weed Killer?

There are several different types of weed killers. Each of them has other functions and benefits to address the different needs of weed control. Let’s take a quick peek at each weedkiller type.

Selective Herbicides vs Non-Selective Herbicides

A non-selective herbicide will target both grassy and wide broadleaf plants. Simply put, it kills everything it comes in contact with within your lawn, garden, and soil. This even includes desirable plants. Non-selective weed killers are suitable for sidewalks, patios, driveways, or any place you don’t want anything to grow.

There are some instances when this type of weedkiller does not eliminate certain plants. One example of non-selective herbicides not killing plants is genetically modified plants. Some genetically modified plants can now resist common non-selective weed killers that contain glyphosate, like Roundup, but this is uncommon.

Selective weed killers are the most popular type of weed killer. A selective weed killer will target only one kind of weed in your lawn. Usually, selective weed killers attack and exhibit weed control on broad-leafed plants, but they can target grassy and woodsy plants as well.

With selective weed killers, it is important always to read the label so you know what type of weeds it can control.

Both selective and non-selective herbicides attack the enzymes in plants. However, the enzymes in broad-leafed plants are different from the enzymes found in grassy plants, which allows them to target specific weeds while preserving others.

Pre-Emergent Herbicides vs Post-Emergent Herbicides

Post-emergent herbicides are used to kill weeds after germination. Post-emergent weed killers can be used on weeds whenever you notice them growing on your lawn. However, for the most effective weed control, use them while the weeds are young and before they start producing and spreading their seeds.

Pre-emergent herbicides are designed to be used before the weeds sprout but are actively growing. Pre-emergent herbicides are great for killing perennial or annual weeds when applied in Autumn. However, be aware, pre-emergent weed killers will not work on weeds after they start to germinate.

Contact Herbicides vs Systemic Herbicides

Systemic weed killers travel down the surface of stems on a weed, are absorbed by the leaves, and eventually penetrate the soil and roots. The chemicals in systemic weed killers work to kill weeds from the inside out.

Contact weed killers kill the part of the plant they directly touch. Contact weed killers damage weeds from above ground. Often, these types of weed killers are homemade and not as permanent as commercial products.

Weed Killer In Action

The right way of applying a weed killer involves the type you use, when to use it, and other important considerations. Let’s learn more about it below.

When Do You Spray Weed Killer?

Generally speaking, a weed killer should be applied or sprayed on your lawn in the early Spring or Autumn when the weeds are actively growing. This helps the weeds absorb more of the weed killer solution.

Of course, different types of weedkiller are best used at different times, so make sure to check the directions on the packaging.

However, early April, when things start to get active in your lawn and again in Autumn, is typically the best time for use. Some find that using weed killer on their lawn yearly is enough, but a biannual basis is more effective overall.

You also want to spray weed killer on your lawn or garden when it is not windy to avoid spreading it to unwanted places. In addition, make sure there is no rain in the forecast for at least a day or two, but three is better. Lastly, try to spray weed killer when it is warm but not overly hot. When it is too hot, the weed killer could evaporate before the weeds and soil thoroughly absorb it.

How Long Does It Take for Weed Killer to Work?

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For the most part, weed killers take about four to six weeks to fully penetrate the root of a weed and kill it for good. In some cases, you may start seeing results in your lawn in as few as five to seven days, but this is often just the beginning.

Contact weed killers may work a bit faster once applied. However, as mentioned above, the effects do not last nearly as long compared to other types of weed killers. You may even need to use contact weed killers every couple of weeks to keep up on your lawn, grass, and garden maintenance.

Are Weed Killers Effective?

Weed killers can be a highly effective way to eliminate weeds in your lawn, primarily if you use the correct type of product for your specific lawn and garden. The main difference when it comes to effectiveness concerns the length of time a weed killer works.

If you are not seeing the results you want at first and are questioning if it will work, we recommend waiting a few more days or weeks before moving on to another solution. Please do not use a higher concentration or apply more than advised, or it could potentially damage your other plants and grass.

Keep Your Lawn and Garden Weed-Free

Now that we have answered our initial question, how does weed killer work, do you think using a weed killer is a good idea for your soil, grass, and plants? Some weed killers target the roots. Others damage weeds on a cellular level. But they all share common goals. These include eliminating weeds and promoting the healthy growth of desirable plants.

If you know your lawn tends to develop weeds, we highly recommend it as an easy and effective way to manage your lawn without continuous upkeep. However, if you are not comfortable applying chemicals to your lawn, there are ways to kill weeds without using a weed killer.

Did you find this article helpful? Do you have other useful tips you’d like to share with others on better weed control? Let’s hear them in the comment box below!