Quick Answer
It is usually recommended to mow your lawn before applying lawn treatments like fertilizer or weed control. Mowing first helps the treatment get down to the grass roots and soil more effectively. However, there are some exceptions where you may want to treat first and then mow later. Read on for more details.
The Benefits of Mowing Before Treatment
Mowing your lawn before applying treatments offers several advantages:
Allows the Treatment to Reach the Soil
When you mow first, it removes some of the height and thickness of the grass blades. This allows liquid or granular treatments to more easily fall down to the soil level where the grass roots are growing. Getting the nutrients, herbicides, pesticides etc. down to the roots and soil is key for the products to work effectively.
Creates Even Distribution
Long, uneven grass can prevent treatments from reaching the lower areas of the lawn. Mowing creates an evenly cut surface, which leads to even application of the product across the entire lawn.
Reduces Risk of Product Runoff
If the lawn is overgrown when applying treatment, the product is more likely to get caught up on the grass blades before absorbing into the soil. This can lead to issues like fertilizer runoff into drains, ponds, or gardens. Mowing first shortens the blades to allow better product absorption.
Prevents Matting and Growth Issues
Applying product onto long, uncut grass can lead to matting, uneven growth, and collection of debris. Mowing ensures the grass blades stand up straight to receive the full benefits of the treatments.
Makes it Easier to Spot Missed Patches
An evenly mowed lawn makes it obvious if any patches were missed during treatment application. You can go back and touch up any missed spots more easily compared to spotting them in tall, uneven grass.
Encourages Desired Growth
Mowing encourages new growth from the soil level, which takes advantage of the benefits of recently applied nutrients, weed control, and other lawn products.
Sets up the Lawn for Success
Starting with a clean, even, freshly cut lawn sets your yard up for maximum results from liquid or granular treatments. The products can fully absorb and spread evenly across the soil and roots.
When to Treat Before Mowing
While mowing before application is best in most cases, there are some exceptions:
When Using Systemic Weed Killers
Systemic weed killers like dicamba are absorbed into the grass plant and spread down to the roots. Leaving the weeds uncut for a few days allows more chemical absorption before cutting them down.
When Applying Pre-Emergent Herbicides
Pre-emergent weed preventers create a barrier at the soil level to block new weeds. Applying before mowing gives the herbicide time to absorb and become effective before mowing cuts down into it.
When Seeding a New Lawn
It’s best not to mow immediately before or after seeding a new lawn. Wait about 4 weeks after seeding to mow once the new grass is established.
When Managing Lawn Disease
Sometimes lawn diseases like brown patch fungus are better managed by applying treatment first. Delay mowing for about a week to allow the fungicide to work.
When Using Slow-Release Fertilizers
Slow-release fertilizers need time to break down in the soil. It’s best to apply first and wait 1-2 mowings before cutting the grass.
When Using Iron or Chelated Products
Iron/chelated soil supplements for color and growth should be watered in well before mowing. Wait at least a day after application.
Key Tips for Mowing Before Treatment
If you do choose to mow first, follow these tips:
– Mow 2-3 days before treatment for best results. This gives the grass time to recover before applying products.
– Don’t remove more than 1/3 of the grass blade when mowing. Cutting too short stresses the lawn.
– Use a sharp mower blade for clean cuts. Jagged cuts turn brown but clean cuts stay green.
– Mow in a crisscross pattern for an even cut. Make a second pass at a different angle.
– Remove and dispose clippings to prevent any chemical residue. Don’t compost clippings from treated grass.
– Water after mowing to avoid stressing the lawn before treatment.
– Inspect the lawn after mowing and spot treat any weeds before the main application.
What Products to Use Before or After Mowing
Here are some common lawn treatments and when it’s best to apply them:
| Treatment | Apply Before Mowing | Apply After Mowing |
| Nitrogen fertilizer | X | |
| Weed & feed fertilizer | X | |
| Pre-emergent herbicide | X | |
| Post-emergent herbicide | X | |
| Fungicide | X | X |
| Insecticide | X | |
| Soil amendment | X | |
| Grass seed | X |
As shown, products like fertilizer, weed killers, and insecticide are typically more effective when applied after mowing. Meanwhile pre-emergent herbicides, fungicides, soil amendments, and grass seed yield better results applied before cutting the lawn.
How Long to Wait Between Mowing and Treatment
It’s generally best to mow your lawn 2-4 days before applying treatments. This gives the grass blades time to lift back up before application.
If you need to apply something immediately after mowing, wait at least 24 hours if possible. Rushing application right after cutting can damage the grass.
Also be sure to wait the recommended time after treatment before mowing again. This varies by product but is usually 3-7 days.
Let systemic weed killers absorb for 2-3 days before cutting weeds.
Avoid mowing for 1-2 weeks when seeding or managing lawn diseases.
Follow the product label timing recommendations for best results.
Mowing Height for Treatment Application
Mow your lawn on the shorter side, around 2-3 inches, before applying treatments. This gets the products down to the soil level more effectively.
For lawns being seeded, mow to 1-2 inches to allow good seed-to-soil contact.
When managing lawn fungus treat first, then gradually lower mowing height over a few weeks to discourage disease spread.
Higher mowing, around 3-4 inches, reduces stress on the lawn. Go higher if the lawn is struggling or it’s hot and dry.
Remove no more than 1/3 of the total grass blade when mowing before treatment. Cutting too short damages the lawn.
Other Lawn Prep Tips Before Treatment
In addition to mowing, also make sure to:
– Clear away debris like leaves, branches, and toys that block treatment application.
– Remove clippings after mowing to prevent chemical residue from spreading.
– Edge along fences, gardens, and curbs for a clean finish.
– Fill in any holes or low spots to help treatment spread evenly.
– Adjust sprinkler coverage for water to reach all areas.
– Target treat weeds before the main application.
– Read the product label thoroughly before applying anything.
– Allow granular products 1-2 days before expected rain, to avoid runoff.
– Only apply treatments when daytime temperatures are below 85°F.
What to Do After Applying Lawn Treatments
Once you’ve applied fertilizer, weed killers, or other lawn products:
– Water thoroughly after application, unless instructed otherwise. Let granules dissolve first.
– Adhere to the waiting period before mowing again, as listed on the label.
– Avoid walking on treated areas until they have dried. Granules need time to absorb.
– Keep pets off the lawn during the waiting period to prevent chemical exposure.
– Put away unused product supplies, safely out of reach of children and pets. Rinse any equipment after use.
– Apply again as needed on the recommended schedule for best results. Stick to application intervals.
– Watch for expected results within the timeframe listed on the product (2-3 weeks, etc).
– Call a lawn care specialist if issues persist after 2-3 proper treatment applications.
FAQs on Mowing and Applying Lawn Treatments
Should I bag or mulch clippings when mowing before treatment?
Bag and dispose any clippings after mowing before treatment. This prevents chemical residue from spreading as the clippings decompose.
How soon can I mow after applying fertilizer?
Wait at least 24 hours before mowing after fertilizing. 3-5 days is ideal to allow absorption into the soil first. Always check the product label.
What if I already applied weed killer, can I still mow?
If you’ve already treated weeds, wait the recommended time before mowing to allow absorption, typically 2-4 days. Mowing too soon reduces effectiveness.
How do I know if I waited long enough between mowing and treatment?
The grass should fully lift up and regain rigidity, usually taking 2-3 days after mowing. Footprints and mower tracks disappear when ready for treatment.
What if I want to both mow and treat my lawn on the same day?
It’s best to separate mowing and treatment by 2-4 days. But if needed, mow first thing in the morning, then wait at least 5-6 hours before careful application.
Can I mow wet grass after applying treatment?
Avoid mowing wet grass until it fully dries after treatment. Moisture reduces mowing effectiveness and can track chemicals onto hard surfaces.
The Bottom Line
While it depends on the specific products being used, mowing before applying lawn treatments is typically recommended. Cutting the grass first allows fertilizers, weed control, pesticides and other products to better absorb down to the roots and soil. Mowing creates an evenly cut lawn for the most uniform coverage.
However, some situations call for application before mowing. Systemic weed killers, pre-emergent herbicides, newly seeded lawns, and certain disease treatments work better applied to uncut grass.
No matter which order you choose, allow enough time between mowing and product application for grass to fully recover. And always make sure to prep the lawn properly, adhere to label instructions, and take safety precautions when using any chemical treatments.
