How Long Does It Take For Weed Killer To Work?

Weeds can severely impact the health and well-being of your garden or lawn and need to be managed to the fullest extent possible to ensure that you don’t run into any challenges.

However, there are many types of weed killers on the market, each of which is different in many ways.

One of how they differ is how long they take to go into effect.

Understanding these differences is crucial for your lawn care because it can affect what types of products you purchase and make it necessary for you to get high-quality treatment ASAP to minimize complications.

In This Article

First Things First: How Long Should Weed Killer Take to Work?

When you’re shopping for weed killer, the first thing you’re going to notice (perhaps with some frustration) is that there are many options available, each of which makes varying promises.

For example, you may find that one weed killer will destroy growths quickly within a few hours.

However, other types make take days or even a few weeks to reach their full potential.

Why is there such a broad variance in execution times?

Mostly, this variation is due to the unique nature of weeds and how different treatment methods work.

Some use potent chemicals, while others use less strenuous options.

Understanding the differences is critical because it will help you make a careful decision that you may otherwise miss.

Thankfully, the factors you have to understand aren’t too complex if you know a few different elements.

These include:

The Design of the Weed Killer – Some options are designed to be fast-acting to eliminate problematic growth as soon as possible. Others are intended for longer-lasting effectiveness over a lengthier period. As a result, the options you choose must be based on your needs.
The Type of Weeds – Simply put, different herbicides will work better for specific weeds, requiring you to adjust your choices based on this fact. Ensure that you look at the bag to choose an option that makes sense and buy enough to manage your entire infestation.
The Chemicals Utilized – While there are mostly just a handful of different herbicide options on the market to handle these concerns, each has other effects. Therefore, the type you choose will vary according to your needs and dictate how fast your product works.
The Location of the Weeds – Some weeding situations require a delicate approach, one that considers factors that may otherwise be hard to understand. For instance, weeds in flower beds need specialized herbicides that don’t impact the health of your beautiful blooms.

As you can see, many factors impact just how fast your weed killer will work.

However, there are many other considerations that you need to consider before buying any of these products.

We set them down in separate sections below because they require more specialized attention.

Just as importantly, these elements are often quite complex and deserve more attention.

Thankfully, they aren’t too complicated that you shouldn’t be able to understand them easily.

Though some scientific terms may be used here, none are too technical for the average home or garden owner.

Understanding the Types of Weed Killers and How They Work

The various weed killers on the market typically fall into a handful of different categories.

Each of these variations is important to understand if you want to choose a weed killer that makes sense for you.

And while quick weed management is often a good thing, speed doesn’t necessarily indicate comprehensive treatment.

Sometimes, you may want a slower-acting weed killer to get long-lasting results.

Contact Weed Killers – Work in Hours

If you want fast-acting relief from weeds, contact weed killers are typically the best option for your needs.

These products work as soon as they touch weeds and usually kill them in a few hours.

They use very potent chemical mixtures to create this effect and work on emergent weed growths.

So if these weed killers work so fast, why aren’t they the only type available on the market?

However, they do have some downsides that must be considered if you want to buy them.

Remember – all herbicides have different pros and cons that must be weighed.

Pros of these weed killers include:

Quick-Acting Speed – As mentioned previously, you should see your weeds die in a matter of a few hours with contact weed killers. It may take up to a day for some of these options to go into effect, though this is usually quite rare.
Inexpensive Purchase Price – Most weed killers of this type are usually relatively inexpensive and are often considered the most common hand-held option on the market. They are also readily available and provide you with cost savings when used correctly.
Easy to Apply – As mentioned above, most contact weed killers come in a hand-held spray bottle that you can use to attack emergent weeds with ease. Spray it directly on your weeds, and they should quickly die, leaving you with a lawn free of weeds.

The downsides of this option include no pre-emergent weed management and a non-specific treatment method.

In other words, these weed killers may kill other plants if you aren’t careful, meaning you need to be very specific about where you apply them.

And they don’t stop weeds from growing again.

Pre-Emergent Pesticides – Take Longer But Also Last Longer

Pre-emergent weed killers differ from contact options because they are designed to kill weeds before they emerge.

Like all other plants, weeds have a lengthy rooting and growing period, meaning it may take several weeks before they emerge from your lawn fully grown.

However, pre-emergent weed killers help by killing seedlings and roots, stopping weeds before they become mature.

There are many reasons why you may want to consider this option for your yard over a contact killer.

These benefits include:

Long-Term Protection – As you can imagine, a yard free of weeds for up to three weeks is a significant benefit. However, taking care of the long-term health of your lawn may require pre-emergency herbicides, mainly when applied smoothly and efficiently.
Non-Specific – These herbicides are designed to be non-specific, meaning that they’ll kill just about any weed in your lawn. While you still need to be careful when applying it around delicate plants and flowers, you should be able to handle most of your weeds.
Don’t Damage Mature Plants – That said, pre-emergence herbicides don’t attack adult plants, including flowers and other growths. So you only need to be careful with spreading these weed killers near seedling areas, minimizing where you place them to avoid long-term gardening complications.

It is important to remember that these weed killers do NOT attack emergent weeds.

And it typically takes them a week or so to kill seedlings when they go into effect.

Though not significant, these downsides are essential to consider – slower and more effective treatment vs. immediate care must be debated.

Emergent Weed Killers – Efficient and Quick

If pre-emergent weed killers destroy seedlings before they become mature plants, emergent weed killers do the opposite.

In addition, they differ from contact weed killers in their speed of effectiveness, as they may take a day or more before you start to see results.

Some may take up to a week.

As you can imagine, this option has benefits and downsides that must be considered before you buy one.

You’ve probably noted that trend already, right?

In any case, these advantages will vary based on the type you buy, but they usually help to:

Manage Sprouting Growths – If you already have weeds spreading throughout your yard, this type of herbicide can help by getting rid of them quickly and efficiently. You’ll then have little to worry about when it comes time to weed or pick your garden.
Decrease Costs – Emergent weed killers are typically less expensive than other options because they are designed for a more active and less long-term role. As a result, they are often a good choice for people on a specific budget.
Varying Levels of Selection – Typically, you want to buy an herbicide to kill as many weeds as possible. However, you may also have a specific growth problem that needs particular treatments. Try to find a good balance here to minimize your confusion.

The downsides of this option include a shorter-term solution and an inability to destroy pre-emergent growths.

Therefore, it is usually a better idea to choose this type of treatment if you already have active developments in your yard that must be destroyed.

However, they can be used in combination with pre-emergent options to handle all of your weed needs.

Careful Application of Each Weed Killer

The effectiveness of your herbicide will vary depending on when you apply it.

If you don’t follow a specific application pattern, you may end up with a poor weed killer spread that impacts how well you manage these growths.

These schedules will vary according to the type you use:

Contact Sprays – Typically, you should spray these herbicides directly on the plants you want to kill on the day that you want them killed. You usually need temperatures between 60-85 degrees Fahrenheit to get good results. Make sure to let the herbicide soak into the weeds to get great results.
Pre-Emergent Weed Killers – Typically, you need to spray these herbicides on your ground when the soil temperature is at least 50 degrees Fahrenheit for 3-5 days. You typically get the best results if you spray them in the early spring, as this is when most weed seeds are ready to sprout.
Emergent Weed Herbicide – You can usually spray emergent weed killer most times of the year and get great results. However, most people will try to do it in late spring or early summer or late fall to early winter. During this time, most emergent weeds should be easier to see.

Does the selectiveness of a weed killer impact when it should be applied?

Not really.

Usually, you follow these guidelines with any weed killer you plan on spraying, regardless of whether it is selective or a more general option.

That said, you should be careful about where you apply it.

For instance, it is best to focus your selective weed killers on a more general area of your yard.

It is wasteful to spread them over a whole yard if you only attack a specific section or a particular type of weed.

Following this approach helps you save money, too, by minimizing your spray amount.

Picking a Weed Killer

Before you make a purchase, weigh all of these factors, focusing heavily on elements like the overall speed, effectiveness, and usage of your treatment method.

Then, you should make sure that you follow all of the instructions on the treatment bag to minimize any complications.

This simple process should give you the help you need.