The arrival of spring brings with it a welcome surge of life, including the green shoots of unwanted weeds. To combat this, many homeowners turn to pre-emergent herbicides, a powerful tool in the fight for a pristine lawn. But a common question arises: should you mow before you apply? The answer, like most things in gardening, is not so simple. This article dives into the nuances of pre-emergent application, exploring the pros and cons of mowing beforehand, ultimately guiding you towards the best practice for your lawn.
In short, whether or not you should mow before applying pre-emergent depends on the specific type of pre-emergent and the current state of your lawn. Some pre-emergents require contact with soil for optimal effectiveness, while others work best when applied to actively growing grass. Additionally, the height of your lawn plays a role in the application process.
Why Do You Apply Pre-Emergent?
Pre-emergent herbicides are designed to prevent weed seeds from germinating. They work by creating a barrier in the soil that disrupts the growth process of weed seedlings. This makes them an excellent preventative measure against common lawn weeds like crabgrass, dandelions, and clover.
How Pre-Emergents Work
Pre-emergent herbicides work by interfering with the development of the weed seedling’s root system. They contain active ingredients that target specific processes in the plant’s growth cycle, effectively stopping it before it even breaks through the soil.
Types of Pre-Emergent Herbicides
Pre-emergent herbicides come in various formulations, each with its own unique properties and application methods. Some common types include:
- Granular pre-emergents: These are typically easier to apply and tend to be more cost-effective.
- Liquid pre-emergents: These offer more precise application and can be mixed with other lawn care products.
Mowing Before Applying Pre-Emergent: The Pros and Cons
Now, let’s delve into the debate of whether to mow before applying pre-emergent.
Pros of Mowing Before Applying
- Improved Coverage: Mowing your lawn before applying pre-emergent can help ensure that the herbicide reaches the soil more evenly. This is especially important for granular pre-emergents, which can sometimes clump together in long grass.
- Reduced Risk of Burning: Some pre-emergents can damage or burn actively growing grass if applied directly to the leaves. Mowing beforehand reduces the risk of this happening by removing the uppermost layers of grass.
Cons of Mowing Before Applying
- Possible Dilution: Some pre-emergent herbicides require direct contact with the soil to be effective. Mowing can potentially dilute the concentration of the herbicide in the soil, making it less effective.
- Delayed Application: Mowing your lawn adds an extra step to the process, which can delay the application of the pre-emergent and potentially allow weed seeds to germinate.
The Best Approach: A Case-by-Case Assessment
The decision of whether or not to mow before applying pre-emergent ultimately depends on the following factors:
1. The Specific Pre-Emergent
- Pre-emergents that require soil contact: These are typically more effective when applied to the soil directly. In this case, mowing beforehand may be beneficial for improved coverage, but it’s crucial to follow the product label instructions carefully.
- Pre-emergents that require contact with grass: Some pre-emergents require the grass to be actively growing for optimal absorption. If you are using this type, it’s generally best to apply the pre-emergent after mowing.
2. The Current State of Your Lawn
- Tall, thick grass: Mowing before application can help ensure the pre-emergent reaches the soil more evenly.
- Short, trimmed grass: If your grass is already relatively short, mowing beforehand may not be necessary.
3. The Time of Year
- Early spring: Weed seeds are often still dormant in early spring. This is an ideal time to apply pre-emergent, and mowing beforehand can be helpful for improved coverage.
- Late spring or summer: As weeds begin to germinate, mowing can potentially disrupt the pre-emergent’s effectiveness.
Additional Considerations
- Always check the product label: The best practice is to consult the product label for specific instructions on the ideal application timing and method for the pre-emergent you are using.
- Use a spreader for granular pre-emergents: Using a spreader ensures even distribution of the product and helps prevent over-application.
- Avoid applying pre-emergent during hot, dry conditions: Pre-emergent herbicides can be more harmful to your lawn during hot, dry weather.
- Water the lawn after application: Watering helps activate the pre-emergent and ensures it penetrates the soil effectively.
Conclusion
The decision of whether to mow before applying pre-emergent requires careful consideration of the specific pre-emergent product, the current state of your lawn, and the time of year. Always prioritize the instructions on the product label and adapt your approach based on your lawn’s unique needs. By carefully weighing these factors, you can make an informed choice that maximizes the effectiveness of your pre-emergent application and helps you achieve a healthy, weed-free lawn.
Frequently Asked Questions
1. What is pre-emergent herbicide?
Pre-emergent herbicide is a type of weed control product that prevents weed seeds from germinating. It works by forming a barrier in the soil that prevents the seeds from accessing the nutrients they need to sprout. Pre-emergent herbicides are often used to control annual weeds, which are weeds that grow from seed each year.
There are many different types of pre-emergent herbicides available, and each one is formulated to target specific types of weeds. It is important to choose a pre-emergent herbicide that is specifically designed to control the weeds you are trying to prevent.
2. When is the best time to apply pre-emergent herbicide?
The best time to apply pre-emergent herbicide is before the weeds have a chance to germinate. This means applying it in the early spring, before the soil temperature warms up and the weed seeds begin to sprout. However, it’s important to check the product’s label for specific instructions.
You may need to apply multiple applications throughout the growing season to keep weeds at bay, especially if there are prolonged periods of rain or drought. Always follow the manufacturer’s instructions for application rates and timing.
3. How does mowing affect pre-emergent herbicide application?
Mowing your lawn before applying pre-emergent herbicide can actually make the application more effective. When you mow, you remove the grass blades that can block the pre-emergent herbicide from reaching the soil. This allows the herbicide to penetrate the soil and create a barrier that is more effective at preventing weed seeds from germinating.
However, it is important to mow your lawn a day or two before applying the pre-emergent herbicide. This will give the grass blades a chance to regrow, and it will also help to ensure that the herbicide is evenly distributed across the lawn.
4. What if I mow my lawn after applying pre-emergent herbicide?
Mowing your lawn after applying pre-emergent herbicide is generally fine. However, it is important to avoid mowing too close to the ground, as this can damage the grass and make it more susceptible to weeds. It is also important to avoid scalping the lawn, which is when you cut the grass blades too short.
Scalping the lawn can damage the grass roots and make it more difficult for the pre-emergent herbicide to work effectively. It is best to mow your lawn at a height of 2-3 inches.
5. Will mowing interfere with the effectiveness of the pre-emergent herbicide?
Mowing itself doesn’t interfere with the effectiveness of pre-emergent herbicide. The herbicide has already formed a barrier in the soil, and mowing won’t disrupt that barrier. However, if you mow too close to the ground, it can expose the soil and make it more vulnerable to weed seeds.
The most important factor is making sure the pre-emergent herbicide is properly applied and has enough time to penetrate the soil before mowing.
6. Is it better to apply pre-emergent before or after a rainfall?
Applying pre-emergent herbicide before a rainfall can increase its effectiveness. The water from the rain helps the herbicide to penetrate the soil and create a more effective barrier against weed seeds. However, if you apply the pre-emergent herbicide right before a heavy rainfall, there’s a chance it could be washed away before it has time to work.
It is always best to check the product label for specific instructions on how to apply the pre-emergent herbicide.
7. Is there any other advice for applying pre-emergent herbicide?
Here are some additional tips for applying pre-emergent herbicide:
- Read the product label carefully before applying any herbicide.
- Wear gloves, eye protection, and other protective gear when handling herbicides.
- Avoid spraying herbicide on windy days, as this can cause drift and damage to nearby plants.
- Water the lawn thoroughly after applying the herbicide to help it penetrate the soil.
- Remember that pre-emergent herbicides are not a one-time solution. You may need to apply multiple applications throughout the growing season to keep weeds at bay.