Overseeding a Lawn with Weeds: Should You Kill Weeds First?
A lawn full of weeds can become even more problematic if you don’t overseed the right way. Overseeding is meant to renew your lawn, fill in any bare spots, and make the turf dense. But, when your lawn is full of weeds, should you go ahead and overseed without killing weeds first?
Overseed your lawn in the fall after killing weeds in late summer. If you’re late, scalp the weedy lawn, rake away all the debris, and spread grass seed. Some weeds will germinate and grow with the grass, but you can control them using a post-emergent herbicide before they spread further.
It is not a good idea to plant and grow new grass over weeds because weeds compete for nutrients and water in the soil, which leads to poor germination and growth of the newly planted grass.
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Should I Kill Weeds Before Overseeding?
Kill and remove weeds from your lawn at least 6 weeks before overseeding if you’re using a post-emergent herbicide. Alternatively, remove weeds by hand-pulling manually. Weed killers will affect the seed germination, so, allow enough time as indicated on the product label before planting grass seed.
Since the best time to overseed most lawns is fall, late summer is a good time to put down a post-emergent weed killer. By the time fall comes, it will be at least 4-6 weeks since you applied a weed killer, which is safe for planting grass seed.
How to Overseed a Weedy Lawn
It is best to kill weeds first before overseeding.
Weeds like bare spots and can continue to spread and invade your lawn if you don’t do anything about them. That’s why overseeding helps control them by making your lawn thicker and fuller, and able to choke out weeds.
Overseeding is time and cost-effective, as you don’t have to till and tear apart your lawn. Instead, you’re breathing life back by adding more grass seeds on top of an existing lawn. If done right, this technique lets you grow enough lush lawn that fills in the bare or thin patches in your yard, leaving no room for weeds to grow.
Here’s how to overseed a lawn with weeds:
1. Pull out the weeds manually
Remove weeds from your lawn manually using a weed puller. Pulling weeds out by hand is highly recommended especially if the weeds are grown and visible. Do not apply herbicides on your lawn before overseeding as this can cause poor germination of grass seed.
If you prefer using a weed killer before overseeding, do so early enough to allow time for the herbicide to break down completely before spreading grass seed. Most pre-emergents and post-emergent herbicides have indicated waiting periods before you plant grass seed.
Here’s how to pull out weeds by hand:
- Water your lawn deeply to make the soil soft.
- Pull out weeds by hand or using a weed puller.
- Throw the weeds away from your yard.
In some cases, you may not need to apply a weed killer as weeds like crabgrass usually die off as the weather becomes cooler. If you have annual weeds, just overseed your lawn with weeds late in the fall and allow the new grass to grow. By the time spring comes, your lawn will grow thick and full enough to choke most annual grassy weeds.
2. Mow the lawn on the lowest setting
Set your mower to the lowest setting possible in order to scalp the lawn you want to overseed. Scalping your lawn helps improve the seed-to-soil contact that in turn improves the rate of seed germination. Set your lawn mower’s deck as low as possible – though any setting between 1.5 and 2 inches would be a good option to consider if the lawn does not have too many weeds.
- If your lawn is level, you can set the mowing deck as low as 1 inch from the ground.
- If your lawn is bumpy, set the blades a little higher – up to 2 inches to prevent damaging the blades.
Pro tip: Always bag clippings if your lawn has weeds that have gone to seed to prevent spreading weed seeds all over your yard and worsening the problem.
It is also a good idea, in my experience, to mow right before the rainy week to keep the lawn moist. It makes my mowing job a lot easier as the grass is soft and the thatch easy to remove right before overseeding weedy lawns.
3. Remove grass clippings
Use a rake to remove grass clippings and other debris that’s covering the soil. The process of raking also helps loosen up the top soil in your yard.
If you mowed a little higher, you might have a lot of thatch remaining on the soil surface. Use a heavy duty rake to remove any debris that can prevent your grass seed from staying in contact with the soil for germination.
A good rake can also help you remove any moss that may be growing under the grass in your lawn.
4. Dethatch the lawn
A thick layer of thatch can also cause seed to soil contact problems. Use a dethatcher to break down the thick thatch and then collect the loosened-up trash bag and throw it away on your compost.
Alternatively, run a power rake all over the weedy lawn to loosen up any thatch and tangled-up grass.
When I have a large weedy lawn to overseed, I find it helpful to rent a slit seeder to complete the task in the shortest time possible.
5. Aerate the lawn
By the time it is fall, the soil is usually compacted already, which is why the grass in your yard is growing slowly while the weeds grow faster. After removing the weeds, mowing, and dethatching, core aerate the lawn to allow air, water, and nutrients to be easily accessed in the root zone.
The cores created in the yard will also allow for better seed-to-soil contact as soon as you overseed. This process is better than just sprinkling grass all over the lawn because it improves the rate of seed germination.
6: Spread the grass Seed
Spread grass seed over the prepared area using a lawn spreader. Follow the recommended spreader settings for the type and variety of grass seed you’re overseeding your lawn with to ensure you’ve put down enough make your turf thick and full the next season.
Pro tip: Spread a thin layer of straw to cover grass seed and prevent birds from causing damage. You can also use bird deterrents if you don’t want to cover the grass seed.
For the best results, plant one-half of the grass seeds in one direction and the other half in the opposite direction. I recommend using a lawn spreader for even distribution of the seeds.
Also, you need to make sure the seeds have a good contact with the soil because this helps with proper germination and enhances growth. You can use a water-filled roller or the back of metal rake to establish the recommended contact between the soil and your grass seeds.
7. Gently rake in the grass seed
Raking is important as it helps the seeds come into contact with the soil to germinate properly. If you used a spreader or simply broadcast the seeds with your hand, the grass seed isn’t in proper contact with the soil.
Lightly rake in the seed over the overseeded area to improve contact and promote faster germination. Raking will also prevent water from washing away seeds in your lawn when you irrigate.
8. Water your overseeded lawn lightly
Water the overseeded area lightly to keep the soil moist enough for the grass seeds to germinate and grow. Do not use a heavy sprinkler because it can easily erode the seeds away from the desired area.
Here’s a video on how to prepare and overseed a lawn with weeds:
How to Control Weeds after Overseeding
Weeds may sprout in your lawn soon after your grass seed starts to germinate. At this time, do not apply herbicides yet. Applying herbicides too soon can kill or weaken the young grass shoots.
Wait until the roots have established and the crown matured enough to withstand the strength and effect of the chemicals.
Also, instead of using equipment such as a power rake, which disrupts lawn surfaces, use less disruptive tools such as a hand rake, as they cause less disruption and don’t leave bare patches on the lawn.
Overseed your lawn at the right time to reduce weed competition and enhance the dramatic, successful growth of the overseeding process. You can overseed cool season turf grasses between mid-August and mid-September as a way to fix a weedy yard. These are favorable times for their germination and establishment.
Can I overseed after weed and feed?
It is not recommended to overseed your lawn after applying weed and feed fertilizer. This type of lawn food contains herbicides that can inhibit germination of both grass and weed seeds. If you’ve just put down weed and feed, wait at least 6 weeks before sowing grass seed.
Read the weed and feed product label for the recommended time to wait before reseeding your lawn. Follow the instructions to ensure you achieve a high germination rate when overseeding a weedy yard.
While fall is the perfect time to overseed your lawn and encourage weed control, there are other seasons to overseed provided you understand the risks.
You can overseed in the early spring, but make sure the lawn is well drained for the best results. Weed competition is more progressive and intense as spring progresses. So unless you time the overseeding period before weed germination in spring, doing so at this time may not be effective.
Summer is the least desirable time to overseed your lawn especially if it has weeds. In early summer, the conditions are so hot that there’s a huge demand for irrigation for proper overseeding to be possible. This is also the time when broadleaf weeds tend to thrive, and therefore your overseeding efforts are likely to fail.
Overseeding will make your lawn fuller, and thicker; and improve its pest, disease, and weed resistance. Remember, care for and maintain your lawn after reviving its look and density. Some tips include sufficient watering, proper fertilization, consistent weeding, foot traffic control, and proper mowing.
When To Apply Weed and Feed-Complete Year Round Guide
As a Lowes garden manager, one of the most asked questions I get is about healthy, green, weed free lawns. Here are my tips and directions for your Lowes lawn care program applying Sta Green or Scotts.
Weed and feed fertilizer will help improve your lawn.
The number one question: When is the best time to apply weed and feed to my lawn?
Well…it depends really. Where you live, whether you have sun or shade, and lots of other things make a big difference in what your lawn needs. Most regions in the United States can apply weed and feed from March till November.
A well-fed lawn is healthier, which means it has a better root system to combat heat, cold, drought, mowing, foot traffic and other stresses.
One easy to follow rule is to use the summer holidays as your guide.
If you’re going to fertilize, remember the summer holidays of Memorial Day, July 4th and Labor Day as good times to apply.
Weed and Feed Basics and the 4 Step Process
Ok, this is my disclaimer: This is my version of the 4 step program that I have used for years. It works! Make sure you always follow instructions on the bag and use the correct settings on your spreader.
You will find many different versions of weed and feed programs out there. They all will be some variation of the following:
Step 1. Crabgrass Preventer
Step 2. Weed and Feed
Step 3. Summer Fertilizer with Insect Control
Step 4. Fall or Winter Fertilizer
The #1 Mistake: Skipping Step 1 and not using a crabgrass preventer.
The best looking lawns don’t have crabgrass for a reason; they use a crabgrass preventer every year! You can skip it if you want, but I don’t recommend it. Most people don’t realize this, but Scotts Halts and Sta Green Crabgrass both have fertilizer as well in the bag. So take care of the crabgrass and get in that first application of fertilizer.
Your soil supplies some of the nutrients that grass needs but most soils are not able to provide all of them during the entire growing season. Fertilizer helps your lawn stay healthy by promoting new blade and root growth and will aid in recovery from summer foot traffic and pest damage.
Weed & feed is the generic name for a broad range of lawn chemical products designed to strengthen existing grass and kill off certain weeds. It generally improves your lawn’s ability to absorb water and food, and adds necessary nutrients which promote healthy growth. A healthy lawn discourages weed growth and enables a strong root system for your lawn.
The “weed” portion of weed and feed is one of a variety of broad leaf-targeted herbicides, usually Dicamba or 2,4-D, that attacks dandelions, dollarweed, and most other green leafy weeds. The chemical is applied to and absorbed by the leaves of the weed.
The granules will not sit on grass blades, which is why weed and feed generally won’t kill grass unless it is incorrectly applied. There are also liquid forms of weed and feed that are generally applied with a sprayer.
The “feed” portion of weed & feed is a fertilizer that contains some combination of nitrogen, phosphorous, and potassium to green up your lawn. The exact blend of fertilizer ingredients varies by brand, but all products will contain some percentage of nitrogen. Some products also include additional benefits, such as timed-released nitrogen for extended feeding.
When to Weed and Feed With Lowes Sta Green or Scotts
While feeding your lawn once a year will improve its condition, feeding it four times a year will make it even healthier. If you put your lawn on the regular schedule it will stay lush and green all season long.
Fertilize your lawn in the spring, early fall and/or late fall (such as late March, early April, early September and early November). However, if you live in an area with long, cold winters, then late April, August and the end of October may be best.
In most climates, late fall tends to offer better results because that’s when weeds grow stronger roots and take the herbicide to the roots along with it, killing them. You should also never fertilize any cool-season lawn during hot summer months.
If you live in the southern or western parts of the United States, such as Florida, Texas, Alabama or California fertilize your lawn in early summer and again in late summer or early fall. The application process is slightly different if you are using a product for southern lawns, such as Scotts Bonus S.
With all fertilizer schedules, you can add one treatment in midsummer, but avoid fertilizing when the temperature is too hot, particularly when it’s 85 degrees or above.
> Read our guide on southern weed and feed
Some Products Need Dry Lawn, Others Need Wet Lawn
For most areas of the United States, weed and feed products should be applied to a wet lawn either from rain or dew, on a calm day and left on the surface for 24 to 48 hours.
You can also wet the grass with a garden hose or turn on your sprinkler system for a few minutes before applying weed and feed.
The general exception is crabgrass control and southern weed and feed products.
Note: Scotts Bonus S, Sta Green Southern weed and feed and most crabgrass control products should be applied to a dry lawn.
A wet lawn helps fertilizer particles stick to the blades of grass and the weed leaves. To ensure that the particles have the best chance of doing their job, don’t water the lawn again for 48 hours.
If you’ve recently used grass seed, sod or sprigging, wait until your new grass has been mowed at least three times before applying any weed and feed product. For best results use a broadcast spreader set to the level indicated on the product package.
Early Spring: March – April. Step 1
Feeding your lawn in the spring strengthens roots and gets it off to a good start. Crabgrass control is the number one reason to use a pre-emergent fertilzer. If you had crabgrass last year, apply a combination fertilizer with a pre-emergent to control it.
Pre-emergents, such as those commonly used to prevent crabgrass, is weed control which must be applied before the weeds germinate. They are ineffective if the weeds are already actively growing.
You will only have about a 3 week window to apply Step 1. Use Scotts Halts plus Crabgrass Preventer or Sta-Green Crab-Ex Crabgrass Preventer. This early application is the most important part of getting a weed free and healthy green lawn. Yes, use it even if you didn’t have crabgrass last year.
Soil Temperature Map: Find your local ground temperature here
Step 1 should include pre-emergent weed killer and fertilizer used in early spring. This can be from mid March to late April.
Crabgrass normally germinates when the ground temperature reaches 55° F . This is also the ground temperature at which dogwood trees start to bud and forsythias begin blooming.
Late Spring: April – June. Step 2
Spring is prime time for lawns. Your grass is busy growing and using up stored energy. Step 2 weed and feed fertilizer is designed to strengthen existing grass and kill off weeds at the same time. Its also the best time to apply a weed and feed product.
Weeds want sun, water and food, which, is what your lawn needs too. That’s why you want to supply the lawn with a weed and feeding product designed for this time of year. Your grass is growing and unfortunately, broadleaf weeds are actively growing, too. It improves your lawn’s ability to absorb water and nutrients.
Weed & feed has a fertilizer to help “green up” your lawn. It also has a weed killer that targets broadleaf weeds like dandelions and many others. Many weed and feed products also have timed-release nitrogen for extended feeding.
The weed killer in post-emergent types of fertilizers are contact killers, and are effective only if the weeds are already actively growing. They will not kill weeds which have not yet germinated.
Applying in the spring and summer also gives your lawn a nitrogen booster that helps build the roots of your grass. Feed your lawn with a combination of fertilizer with broadleaf weed control like Scotts Turfbuilder with Plus 2 Weed Control or Sta-Green Weed and Feed.
Summer: June – August. Step 3
If you’re going to fertilize, remember the summer holidays of Memorial Day and Labor Day as the best times to apply. But what about summer months? What to do around the Fourth of July? Step 3 weed and feed products are designed for maximum effectiveness with a late-spring to mid summer application. They contain herbicides designed to kill actively growing broadleaf weeds like dandelions.
These herbicides are much more effective if you apply them in the spring or even the fall. At that time, the weeds are either growing or storing up reserves for winter and moving nutrients from the leaves to the roots. They move the herbicide to the roots at the same time, resulting in a better kill.
You can still apply weed and feed in the summer
It is not recommended to apply if the temperature will be above 90 degrees and no re-application of any fertilizer for another 30 days.
Summer is tough on grass. You can still apply a weed and feed product, but do so cautiously. Heat, drought, foot traffic, and insects stress it out. Feeding your lawn in the summer still helps to protect and strengthen it against these problems.
Lawns in warm-season grass areas should be fed over the summer months as they grow steadily from spring to fall. Also consider spot treatment of weeds by using a product such as Ortho Weed B Gon.
A more common problem you will see in the summer months are insects. If you see insects in your grass, use a feeding product that also contains insect control, such as Scotts Turf Builder with SummerGuard. For additional insect control try Ortho Bug B Gon Max granules or try Bug B Gone liquid spray around the perimeter of your home.
Fall: September – November. Step 4
Fall brings back ideal conditions for your lawn. Cool nights, ample rainfall and morning dew all contribute to new growth for your lawn and prime time for Step 4. If you missed an early spring application of weed and feed, now is the time to apply.
Since the lawn is ready to grow again, it is looking for the nutrients it needs to recover from summer damage. Some experts say this is the single most important lawn feeding of the year, more important than an early spring application. Apply your final feeding right before the winter months. You can apply a fall fertilizer until the average daytime temperature is above 50 degrees.
This means most regions of the United States can apply into late October. This will strengthen roots and increase nitrogen storage for an early spring green up next year. Try Scotts Turfbuilder with WinterGuard or Sta Green Weed and Feed Winterizer.
Planting Grass Seed or Aerating after Weed and Feed
Weed & Feed prevents seed germination, so you should avoid planting new grass or aerating your lawn for at least four weeks. If you apply weed and feed in the spring and summer, spread new grass seed and aerate in the fall each year.
Reasons Weed & Feed Didn’t Work
Remember to always follow the directions on the package. Always use a spreader to apply. Here are some common reasons why a weed & feed application could be ineffective:
- Weed & feed targets broadleaf weeds like dandelions, and dollarweeds. It does nothing for crabgrass and other grassy weeds. For these, you should use a pre-emergent like Scotts Halts or Sta-Green Crab Ex crabgrass preventer in the early spring. Must be applied before weeds and crabgrass are growing.
- Mature weeds are not actively growing, so the product will not be as effective. Weed and feed should be applied early in the growing season and a couple days after mowing.
- Rain and sprinklers can wash away the granules. Make sure there is no rain in the forecast and avoid watering for two days after applying.
What if You Apply Too Much Weed & Feed?
The best way to avoid damaging your lawn after too much fertilizer application is to flush out the weed & feed. Water your lawn with 1 to 2 inches of water for about 4 days. It would be best not to apply any other weed & feed fertilizer until the following year. Unfortunately, over watering can create run-off in certain drainage situations, so be aware of your location and where the water is going.
A Healthy Lawn With Lowes Using Scotts or Sta-Green.
Enjoy a lush, healthy lawn with Scotts Turf Builder fertilizer or Lowes exclusive Sta Green Products. Both combine essential nutrients for even feeding and weed control from early spring through late fall. Both provide uniform coverage and improves your lawn’s ability to absorb water and other nutrients to keep it healthy and looking great.
Remember to use the major summer holidays as your guide to the 4 step program: Step 1 Crabgrass in early spring. Step 2 Weed and Feed around Memorial Day. Step 3 Insect Control around July 4th. Step 4 Fall Fertilizer around Labor Day.
The 4 Step Weed and Feed Program-Make Your Own
The 4 step program from Scotts has been around for years. Did you know that it’s officially only available at local hardware stores and not Lowes or Home Depot? But, you can make your own version easily.
The bags sold at independent stores, like Ace Hardware, are a slightly different analysis and the bags will have each step number printed on each bag.
For example, here’s the difference in the first two applications of the 4 step process.
4 step bag: Step 1 for crabgrass ratio: 26-0-03. Step 2 Weed and Feed: 28-0-06
Lowes bag: Comparable Step 1 Halts crabgrass ratio: 30-0-04. Comparable Step 2 Weed and Feed : 28-0-03
Not a big difference. Sure, you can make a 4 step program simply by purchasing the four bags at Lowes or Home Depot, and many of us do, but the actual 4 step Scotts fertilizer program is only available at your local hardware.
Here are a few more helpful guides for weed and feed, grass seed and crabgrass control:
How Many Days Do You Have to Wait Before Seeding After Weed & Feed?
Weed and feed fertilizers are often used in combination with seeding. Weed and feed formulations consist of two components: a herbicide to kill weeds and a fertilizer to strengthen the turf. The herbicide will weaken the grass as well as the weeds and the fertilizer will strengthen the weeds as well as the grass. When applying seed over a weed and feed application, remember that some weed and feeds can prevent grass seeds from growing.
Types of Herbicide
It’s important to know a little about herbicides so you can make the best choice for when to apply seed in an area that has been treated for weeds. The most common types of herbicide in weed and feed products are selective and systemic. Selective herbicides target a species of plant to kill while systemic herbicides work by being absorbed though the roots and then transported throughout the plant, killing it from within. Read the bag label to see what kind of herbicide is used in the weed and feed you are considering using or have used. The bag label will tell you how many days you must wait before applying seed to a lawn that has been treated with that product.
Herbicides can target weeds before they germinate from seed – pre-emergent – or as developed plants – post-emergent. Before you seed, you can use a non-selective, post-emergent herbicide to control any weeds in the area to be seeded. Most of these can be applied up to two weeks before seeding to control any existing weeds. Herbicides should not be used after seeding until the new seedlings are established. Mowing and spot treatments can be used to control weeds until the seeded area is actively growing and requires only maintenance watering. Establishment times vary depending on the type of seed you use and your weather conditions.
Using Weed and Feed
Only use a weed and feed if the weed infestation is completely uniform over the entire lawn and all species of weeds targeted will be affected by the herbicide in the weed and feed. This scenario doesn’t occur often, so it is more likely the use of an herbicide and a fertilizer separately will be needed. If the weeds are uniformly spread over the area to be treated, match the appropriate weed and feed product to your grass, the seed you have recently applied or want to apply, and the time of year.
Know What You Grow
It is important to know what kind of grass you have growing or want to have growing. Certain chemicals act differently on different species of grass and weeds. For example, the common herbicide 2,4-D is toxic to some cultivars of St. Augustine grass (Stenotaphrum secundatum), which grows in the area roughly covered by U.S. Department of Agriculture plant hardiness zones 8 through 10. Another common herbicide, atrazine, is potentially lethal to grass when applied in temperatures above 85 degrees Fahrenheit. Use the instructions on the bag of each weed and feed product to determine how it will affect seeding.
- University of Florida IFAS Extension: Weed Management in Home Lawns
- Texas Agricultural Extension Service: Maintaining St. Augustinegrass Lawns
Sara DeBerry is a graduate of the University of Florida holding a masters degree in environmental horticulture and a minor in entomology and nematology. DeBerry has been writing for government agencies since 2004 and has published peer reviewed scientific articles during her studies at UF.