Overseeding Weedy Lawn—Waste of Time or Effective?
Anyone who’s had to care for a lawn of their own knows how easily weeds can spread. Once they get into your yard, it’s almost impossible to get them out, no matter the number of herbicides you use. That’s because weeds are opportunistic and will claim any bare or thin patch they can find in your yard. But is overseeding weedy lawn areas a good option? Or will the weeds just crowd out your new grass. I’ll discuss in today’s article.
The best way to get rid of weeds, oddly enough, is to grow a lawn lush enough to kick them out.
If weeds don’t have a place to grow, they’ll stay out of your yard.
One of the best ways to reclaim your yard is to periodically overseed it. Overseeding (or spreading grass seed on an established lawn to help it thicken up) is an effective way to improve your lawn, but it’s no quick fix.
It’ll take a good amount of work, but the results are worth the effort if done correctly.
Let’s talk about effectively overseeding weedy lawn areas and the best times of year to do so.
How Overseeding Can Help Your Lawn
Overseeding is the method of revitalizing a yard by adding more seed into an existing lawn.
You don’t have to till your lawn, and you don’t have to tear it up for over-seeding a lawn to be effective.
When you overseed new grass grows to fill in the bare spots of your yard, making it grow in greener and thicker.
Overseeding at the right time of year, before weeds are established or after annual weed pressure begins to ease, will ensure success.
How To Succeed When Overseeding Weedy Lawn Areas
The most important things with overseeding are preparation and timing.
You can’t overseed a weedy lawn in the summer when all of your weeds are mature and growing vigorously. You’ll be wasting your time and money if you try that.
The best times to overseed your lawn are early spring (when soil temperatures are consistently above 55 degreees Fahrenheit) and early-mid autumn.
The time of year when you overseed your weedy lawn will depend upon why you’re doing it in the first place.
If your lawn is thin, and you want it to grow in thicker to prevent weeds from growing, early spring is your better bet.
If you want to give your lawn a hard reset, late autumn is the better choice as your new grass will not have any pressure from annual weeds.
The hot summer months are very harsh for new grass seedlings, so springtime isn’t quite as good for most weedy lawns.
Preparing Your Lawn for Success
Aside from choosing the best time, you must prepare your lawn for overseeding to work the best.
- Cut your grass short. When mowing your lawn normally, you should only cut it by 1/3 its length. But for overseeding, you want the grass short enough to make sure grass seed can get close to the surface. Try cutting the grass by 2/3 its lengths or cut it down to about 1 ½-inches tall.
- Clear your lawn of clippings. After mowing your lawn, make sure there are no clippings on your yard. These can interfere with new grass seed. Either use a bag on your mower or rake them up afterwards.
- Let air into your yard. You want to then loosen up the soil to improve soil contact with the new seeds. This is also a good time to remove thatch from your yard. Either aerate your lawn or use an iron rake to loosen the turf.
Seeding your Lawn
Once these steps are done, it’s time to spread seed onto your yard.
First, choose a grass seed that matches your climate and pairs with your grasses. Also, pick a grass that you can depend on. You want it to grow through the year, and be able to adapt to your yard conditions, like if your yard is sunny or shaded.
Before you begin spreading seed, check the label on the grass seed you purchase for the rate of overseeding. Most bags of grass seed will provide this information right on the bag.
You want to get the right amount of seed in your yard—too much will keep grass from growing because the seedlings compete for moisture, too little and your yard will stay thin and ripe for weed growth.
Once you’ve determined your application rate, use a lawn spreader (broadcast spreaders are my preference) to evenly spread it over your yard, and make sure you spread it on a dry day with no wind.
I like to spread some quick-release starter fertilizer on the lawn before spreading my seed. Scott’s makes a really good product (Amazon link), and it’s particularly good for Spring overseeding because it has a crabgrass preventer in the mix.
Spreading a thin (1/4 inch) layer of compost over the new seed will work wonders to improve germination and help your new seedlings thrive.
You’ll probably want to review my guide to watering new grass to improve your results.
Maintaining Your New Grass
Watering your new grass is critical and knowing the stages of watering is very important.
New grass needs a lot of water, and you want your soil to stay constantly moist.
For new grass, water lightly twice per day for the first week, and water more heavily the second week.
After 2 weeks, water heavily and less frequently. You want the soil saturated down to 6-inches each time you water it past the 2 week point. This will encourage your grass seedlings to grow deep roots which will improve your lawn’s resilience to heat and drought.
Wait several weeks before mowing your lawn.
Make sure the grass is over 3 inches (I recommend 4-inches in height for the first mow), otherwise you risk ripping your seedlings out of the turf because their roots won’t be deep enough yet.
When you do mow, bag your grass clippings the first few times, and adjust your mowing deck to cut no more than 1/3 of the grass blade.
Similarly avoid herbicides for several weeks on new grass.
If you used starter fertilizer, I recommend throwing down organic slow-release fertilizer after 4-6 weeks to sustain and feed your new lawn and keep it healthy.
Annually overseeding weedy lawn areas in combination with the use of pre-emergents every spring will gradually transform your weedy yard into the lush green carpet every homeowner wants.
Lawn myth busting: Skip spring ‘weed and feed’
Editors note: Rossi is a turf specialist and associate professor in the Department of Horticulture, Cornell University. This is the first in a series where Rossi debunks common lawn myths. His advice targets cool-season grass growing regions in the Northeast, but may be applicable in regions with similar growing conditions.
ITHACA, N.Y. – It’s a sure sign of spring: The robins return and millions of lawn owners head out to apply fertilizer and weed- killers to their lawns – a rite widely known as “weed and feed.”
But here’s the problem: Early spring probably isn’t the best time for you to fertilize your grass or apply herbicides unless you have a history of weed problems.
Let’s start with the herbicides. Weed and feed products designed for early-spring application usually contain pre-emergent herbicides. They work by preventing weed seeds from sprouting, and they can be an effective way to control crabgrass and some broadleaf weeds.
Trouble is, this assumes that you’ve got weed seeds in your soil ready to sprout. If you’ve been using pre-emergent herbicides regularly or otherwise doing a good job of controlling weeds and keeping them from going to seed, you may have exhausted the supply of weed seeds in the soil. If that’s the case, applying pre-emergent herbicides is like clapping your hands to keep the lions away.
Then there’s the fertilizer. It should be mostly nitrogen, and I’ll admit that it can really green up the grass in a hurry. But it can also fuel lush top growth at the expense of roots, and you want those roots going deep for moisture so the grass can outcompete weeds during the hot, dry summer months to come. That lush top growth also means you’ll need to mow more often and deal with more clippings.
If you’re going to apply fertilizer, Memorial Day and Labor Day are better times to do it. And with recent restrictions on phosphorus fertilizer in many areas and the lack of evidence that potassium will improve your lawn in most circumstances, shop around for fertilizers that are all nitrogen.
Other weed and feed products are designed for late-spring application. They contain herbicides designed to kill actively growing broadleaf weeds like dandelions. But if you want to kill broadleaf weeds, these herbicides are much more effective if you apply them in fall. At that time, the weeds are 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.
And unless your weeds are running rampant, try spot spraying them in the fall instead of putting down herbicide over your entire lawn. That’s just one small step you can take for sustainability.
If weed and feed has become a ritual for you, it’s time to break the habit. Try skipping it this year and applying fertilizer and herbicide only if you need them and in separate treatments at the times when they will be most effective.