To keep your lawn looking beautiful all season, it’s essential to follow a lawn maintenance routine. Typically, this will include applying a weed treatment and lawn fertilizer at various stages.
A question that often comes up in discussion is whether to mow before or after weed and feed or standard fertilizer applications.
Within this article, I will address this question and provide some insight into the ideal sequence of mowing, feeding, and weeding your lawn.
Types of Lawn Treatments
Before I get into the optimum order of working your lawn, let me first define what I mean when talking about each type of lawn treatment.
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Weed and Feed
The term “weed and feed” is used to describe a fertilizer and herbicide combination that aims to both strengthen lawn vitality and kill any existing weeds or prevent weeds from germinating. These products should only be applied a maximum of twice per year.
Often seen as a single application product in early summer, weed,and feeds are convenient but not as effective as separate pre-emergent weed killers followed by an early summer fertilizer.
Herbicide Spray
Herbicide is a horticultural term used to describe weed killers. There are selective and non-selective herbicides available. Selective herbicides kill specific unwanted weeds such as broadleaf vegetation and therefore some can be used on lawns.
Non-selective herbicides are used to kill everything — weeds, grass, and brush — and should never be used on or around lawns.
Pre-Emergent Weed Killer
Pre-emergent herbicide controls weeds by preventing the seeds from germinating. It works by creating a barrier of chemicals on the soil’s surface.
When the seeds try to sprout, they run into these chemicals and die. Or, in some cases, they coat the seed shell and act prior to the seed sprouting.
Pre-emergent herbicides are applied over fall or early winter and sit on the lawn surface until they are needed.
Lawn Fertilizer Granules
Lawn fertilizer comes in two forms: granules or liquid. Granules are usually broadcast across the lawn surface and dissolve with contact with water and become activated.
Fertilizer pellets are slow-release, meaning they dissolve and release their nutrients into the soil over an extended period. Granules can be applied one or two times per growing season.
Liquid Fertilizer
If you plan on fertilizing your grass more often or require a quick boost of lawn feed, then liquid fertilizer is ideal. Liquid fertilizers can be concentrates or ready-to-use products.
A nitrogen-based lawn spray can be used frequently throughout the year to give a thicker, greener lawn.
Chelated Iron
Chelated iron is a supplement for lawns and plants. This type of supplement helps plants increase iron uptake from the soil. A high soil pH or overly moist soil are often causing iron deficiencies in plants.
Symptoms of plant iron deficiency include pale yellow leaves and eventual overall plant health decline and death. Chelated iron can be used at any point during the growing season.
Should You Apply Weed and Feed Before or After Mowing?
You can apply weed and feed before or after mowing. For optimum performance, I recommend application prior to mowing your lawn.
Most herbicides work by either penetrating the soil down into the root system or by absorption through the weed foliage. Prior to mowing, weeds are actively growing and have a larger foliage surface area for the herbicide to adhere to.
After mowing, weeds will suffer shock and growth will stall temporarily and the foliage surface areas are greatly reduced.
Applying Weed and Feed After Mowing
Ideally, apply weed and feed two days prior to mowing. Water the lawn to activate the herbicide and ensure the weed killer has had time to soak into the lawn and take effect via the weed’s root system or foliage.
The two-day delay will allow the grass to dry and allow the herbicide to be absorbed by the vegetation and begin to work.
Some products may have instructions on correct mowing times depending on the product used. Always read the manufacturer’s label.
In addition, there are different kinds of weed and feed products depending on grass species and climate. Two primary types include cool-season and southern formulations. Each of these product types work on different grasses and zones within the United States.
Cool-Season Formulations
Cool-season grasses live in climates with broad temperature variations within the United States. These climates include most of the United States like the Midwest, Pacific Southwest, and East Coast. Climates such as these experience hot summers and cold winters.
Popular grasses within these climates include perennial ryegrass, Kentucky bluegrass, tall fescues, and fine fescues.
It is important to apply weed and feed during spring and fall and follow the guidance for mowing two days after application.
Southern Formulations
Southern grasses are grasses within the United States that live in climates with warm to hot temperatures year-round. These climates include the Southern United States, including states like Texas, Florida, and all of California.
Popular grasses within these climates include Bahia grass, Bermuda grass, and buffalo grass.
Warm-season grasses require a weed and feed treatment in early spring and can be mowed two days after treatment.
Mowing After Using Weed and Feed
Following application, you should wait approximately two days after using the product to mow your lawn.
This gives time for the herbicide element of the treatment to soak into the soil and begin working prior to any vegetation damage affecting the weed’s ability to absorb the herbicide.
Do not apply to new lawns since these products can be too harsh for young grass. If you have seeded any bare spots in your lawn, do not put weed and feed in these areas as the herbicide will prevent grass seeds from germinating.
Is It Best To Mow Before or After Using Weed Killer?
When using a weed killer for lawns, you have two options: Pre-emergent or post-emergent.
Pre-emergent is applied during late fall or winter, so be sure to do your last mow of the season two days prior to broadcasting your pre-emergent granules over your lawn. You should not need to mow after the application as the grass will be dormant.
If you do need to mow again, make sure to wait at least two days after the pre-emergent has taken on water and soaked into the soil. If you have no rainfall, water the lawn and wait for two days. Then mow your lawn.
Post-emergent weed killer is applied throughout the season on actively growing weeds. Follow the same routine of mowing at least two days before or two days after the application of your post-emergent treatment has been activated by rainfall or by watering your lawn.
Should You Mow Before or After Fertilizing Lawn?
Deciding whether to apply your fertilizer before or after mowing is an often over-complicated thought process. In short, we want as much of the fertilizer to reach the soil as possible. I always recommend mowing before fertilizing the lawn.
Ideally, mow your lawn, then apply the fertilizer the following day and water your lawn. If rain is due, do not water your lawn. Too much water will cause fertilizer run-off and effectively dilute the nutrients entering the soil.
Can I Mow and Fertilize on the Same Day?
Yes, you can. However, do not fertilize immediately after mowing. Instead, wait at least 10 to 12 hours between mowing and fertilizing.
Freshly cut blades of grass have raw ends and need time to heal and build back a protective skin. If fertilizer is applied directly to this raw grass, then the tips of the grass may burn.
Remember some fertilizers are designed for specific purposes and seasons. Clearly, the application of a winter fertilizer should not be followed up by mowing on the same day, as the grass may be dormant.
When applying your fertilizer, it is important to get even coverage and not to over-fertilize your lawn and risk fertilizer burn. To avoid this, I recommend a controlled method of fertilizer application such as a spreader.
Broadcast Spreader
These contraptions look similar to those used to paint baseball lines on a field. They have two wheels, a tub where you put the fertilizer, and get pushed like a mower. Inside the tub is a small blade. The blade’s speed corresponds to the wheels’ speed.
As their name suggests, these spreaders spread the granules over a large lawn area. They are efficient since they spread the fertilizer over a large portion of the ground as you walk. This ensures fertilizer spreads quickly and efficiently. If you have a large lawn, then a broadcast spreader works best.
The pace of fertilizer spread is based on your walking speed. The fertilizer will spread slower and not fling as far if you walk slowly. However, if you walk quickly, more will be output and the force of the blade will fling the fertilizer further.
Drop Spreader
These spreaders look similar to broadcast fertilizers but do not have the spinning blade inside the tub. Instead, they drop the fertilizer between the wheels of the spreader directly onto the ground without flinging anything.
They are particularly handy if you are trying to control the amount of fertilizer getting dropped. Rather than flinging imprecise amounts of fertilizer in all directions, they drop the fertilizer right where you want it.
Drop spreaders always put the same amount of product down no matter how quickly or slowly you walk. They minimize fertilizer waste because broadcast spreaders will often put fertilizer on the sidewalk when you are going around the perimeter of your lawn. Therefore, drop spreaders work well when putting fertilizer close to the sidewalk or street.
Both spreaders have dials that can be set to determine the amount of fertilizer dropped. A wet lawn works best when fertilizing. Fertilize the perimeter of the lawn and then fill the rest in systematically.
Applying Lawn Fertilizer Spray
Fertilizer spray can be applied directly after mowing your lawn. There is very little risk of fertilizer burn and you simultaneously are watering it in.
Many liquid lawn fertilizers can be attached to the end of your garden hose, and then you can fertilize your lawn while simultaneously watering it. Or you can purchase a concentrate that requires diluting in a pressure sprayer or backpack sprayer.
You can also use your sprinkler system to fertilize your lawn by diluting the mixture with water and using a sprinkling can. The recommended dilution is one pound of fertilizer to 1,000 square feet.
Applying Chelated Iron
Chelated iron can be applied to the lawn at any point during the growing season. It is readily available in liquid concentrate form and therefore is applied as a spray.
For the best result, I recommend applying chelated iron after mowing. This will enable spray droplets to reach the soil and get to work.
Best Time to Apply Lawn Treatments
Each lawn treatment has an optimal time for application. After all, that’s what they are designed for, right?
Pre-Emergent Weed Killer
You should apply pre-emergent weed killer for cool-season grass in early spring before weeds have sprouted. Ideally, the best temperature to apply pre-emergent weed killer is when the grass temperature has stayed about 55 degrees Fahrenheit for 48 hours.
Post-Emergent Weed Killer
Like pre-emergent weed killers, post-emergent weed killers should be used in early spring in cool-season climates. Post-emergent weed killer should be applied in the morning when weeds actively absorb nutrients and grow fastest. As the day progresses, weed growth slows. If rain is in the forecast, it’s best to apply the weed killer before the showers can wash it away.
Weed and Feed
Like weed killer, weed and feed should be applied in the early spring when the grass is beginning to wake up from its winter dormancy. Apply the product after the grass has begun growing and weeds are sprouting.
Wait a few weeks so your lawn has time to recover before reapplying. If you have seeded your lawn, wait until after mowing it at least twice before weeding and feeding it.
Lawn Fertilizer
You can apply lawn fertilizer up to three times a year in cool-season climates — in the spring, early summer, and late fall. Use high-nitrogen fertilizer to help green the grass in the spring and early summer. A winterizing fertilizer mixture should be used in fall before the year’s first snow.
Verdict: When To Mow When Using Weed and Feed
In summary, it is important to mow your lawn at least two days after the application and activating of combined weed and feed products. This will allow time for the herbicide ingredient to reach the weed vegetation or root system and become active.
When applying lawn fertilizer, I always recommend mowing prior to fertilizing the lawn. The reduction in the grass will assist the fertilizer product in making direct contact with the soil of the lawn and getting the nutrients down into the grassroots.
