As most homeowners and gardeners know, letting a weed problem get out of control is one of the best ways to end up with an ugly lawn. And that means that controlling weed growth is one of the most essential things to do if you want the loveliest lawn on the block. Today, I’m going to talk about a weed called Poa Annua, also called Annual Meadow Grass but in America it’s often referred to as Annual Bluegrass or simply Poa. I’ll share some photos that will help you identify Poa Annua in your lawn, and give you my tips to kill it in your lawn.
If you have poa annua on your lawn, it’s time to take steps to eliminate it and restore the beauty of your property.
I’ve got a big, in-depth article for you that covers everything you need to know about the poa annua weed, so lets get started.
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What is Poa Annua Weed?
You may hear some people refer to poa annua as “annual bluegrass,” “annual meadow grass” or simply “poa.” They’re all talking about Poa Annua – a grassy weed that germinates between the late part of summer and the early part of fall.
For some homeowners if a plant looks and grows like grass, it is grass and it’s desirable for a lawn.
But for many of us – undesirable grasses that grow at a different rate, to a different height, or which stand out as a different color than the desirable turfgrass in our lawns is a weed.
If you’ve got Poa Annua growing in your lawn, you may notice it starts looking unpleasant in the spring months.
That is the time of year when there is the first blooming of the seed heads. It happens even more in the summer.
In fact, summer is when poa annua looks worst. That is because it turns an unpleasant brown when it dies in the heat, creating bare patches in your lawn where you thought you had nice thick turf.
This is when many homeowners notice this weed and get alarmed about how it’s affecting their lawn and its aesthetics.
Poa annua seedling growth takes place all through the fall months, but this weed’s flowering occurs in the spring.
What Does Poa Annua Weed Look Like?
If poa annua has already grown on your lawn, you’ll see tall seed stalks with a tasseled look. This weed has a brighter shade of green than you’d expect, and it may be bright green when the rest of your lawn is dormant.
Poa annua usually has fine-textured leaves. However, it generally grows in clumps.
In most cases, these will grow taller than the remainder of your lawn (your desirable lawn turfgrass).
The times of year when you will probably most notice this are the early parts of the summer, and even the later part of the spring.
Some homeowners believe that if they just cut the seed stalks, they can stop the weed from growing. Unfortunately, the opposite is true!
In fact, if you cut them down to a shorter height, the stalks can still create seeds.
When it comes to the summer heat, poa annua becomes an even greater nuisance.
That is because it will turn brown and die back, and this will end up in your lawn having alarmingly unattractive brown spots.
Poa Annua Photos for Identification
Where Does Poa Annua Weed Grow?
Poa annua is most likely to grow in excessively moist areas of soil. It also thrives in compacted soil.
Compaction is also a problem for your turfgrass because it stops its roots from getting all the nutrition and water it needs.
This is just one reason you should aerate your lawn’s soil on a regular basis. Aeration involves breaking up and loosening the soil.
Is Poa Annua Weed a Perennial or Annual Weed?
While poa annua is an annual weed, the seeds are incredibly resilient. In fact, they may exist dormant in a lawn’s soil for several years, waiting for favorable conditions.
As long as the seed stays viable, this weed can start growing as soon as conditions are right.
Given this reality, you’ll probably have to go through two steps to get rid of poa annua in your lawn.
It’s the fact that hot temperatures make poa annua die back and turn brown that makes it such a problem for many homeowners.
In some cases, you may not even notice the problem until the brown spots appear. You may even have empty spots on your lawn.
One of the trickiest aspects of poa annual is how it starts growing more when the weather is cool. After all, this is when your turfgrass won’t be resilient.
In fact, it will probably be dying back and the soil will be more susceptible to being overtaken by weed growth, including poa annua.
By using a pre-emergent herbicide, you are more likely to have success with getting rid of this weed.
How to Get Rid of Poa Annua in Your Lawn or Garden?
Of course, you can start out by simply pulling out the poa annua with your hands. However, this isn’t likely to be a permanent solution, as the weed can grow back from the resilient seeds already in the soil.
If your poa annua problem isn’t already fully established and you’re lucky, pulling out the visible weeds may be sufficient.
But if you have large and fully established patches of this weed, digging them up and pulling them probably won’t be enough.
In other words, you will probably have to use herbicides.
Using Pre-Emergent Herbicide to Kill Poa Annua
Pre-emergent herbicide is an important substance in treating poa annua in your lawn, and you can find a full list of my recommended products in this category right here.
But if you’re looking for a quick recommendation, here are three options that will work well:
Best Pre Emergent for Poa Annua in Lawn
Please note that none of these products will kill existing Poa Annua in your lawn.
Pre emergent herbicides block the seeds from germinating so they prevent growth in subsequent seasons. It’s still the best way to get rid of this persistent annual weed.
I’ve had great success with these products from The Andersons – an American company based in Ohio that offers a 100% satisfaction guarantee. They’ve offered my readers a special discount and you can SAVE 10% off your order if you use the code LAWNCHICK at checkout on their website.
When to Apply Your Poa Annua Pre Emergent Treatment
For major infestations of Poa Annua in lawns, most experts recommend that you do three pre-emergent applications annually.
You’ll want to do two applications in the fall with 6-8 weeks in between applications and the second application complete before your local soil temperatures dip below 70 degrees.
Greencast/Syngenta has a nice tool you can use to estimate the soil temperature trend in your region based on historical data. This will help you plan your annual application dates.
But always remember, with any kind of weed treatment, your region and climate will play a part in how you time weed-control applications, and how many you actually need to do.
For example, in some northern climates, you may only need a single fall application and one in the spring.
Read the instructions that come with your weed control products, and use the soil temperature tool linked above to make a schedule that will work for your lawn.
Why Pre-Emergent Usually Isn’t Enough for Poa Annua
Even if you apply a pre-emergent correctly and in a timely way, you will probably have to use a post-emergent herbicide, too.
Obviously, using a pre-emergent herbicide will cut down on how much poa annua you will see when it grows, but there will probably still be some that gets through.
That is where a post-emergent herbicide (a weed killer that kills actively growing weeds) comes in.
Best Post-Emergent Herbicide For Poa Annua
Remember that poa annua is a cool-season plant.
That’s why you’ll have to be extremely careful when applying post-emergent herbicide if you have a cool-season grass lawn. The herbicide could damage or even kill your grass, so you will have to weigh that when deciding if you want to use a post-emergent herbicide to kill actively growing Poa Annua.
If you do, the use of pre-emergent herbicides may make it difficult to repair those patches where your lawn died due to treatment.
Many pre-emergents block all seeds from germinating, including grass seed.
The Unique Challenges of Annual Bluegrass
Remember, poa annua is a stubborn weed, and it tends to blend into the rest of your lawn, especially if you have a cool-season variety of grass.
In many cases, you will have to continue doing both pre-emergent and post-emergent weed treatments in order to entirely eliminate poa annua from your property.
One of the trickiest aspects of getting rid of poa annua is the reality that there are very few selective herbicides that work on this weed (though I share one that can work below).
A selective treatment means that it will only kill the weed you want to eliminate, without hurting your turfgrass.
Unfortunately, most selective herbicides that will kill poa annua are only able to be used by lawncare professionals with certification.
So, if you want to use any of these, you will have to hire these experts.
A Word of Caution
Of course, if you want to do it on your own, there are non-selective herbicides you can use. But if you use these, you will have to be extremely careful.
Read the instructions, apply mindfully only to the weeds, and thoroughly read and understand the product instructions.
If you get things wrong, you could end up killing your whole lawn.
Of course, if this happens, you should be able to start all over again by calculating how much grass seed you’ll need and planting a new lawn, but many homeowners aren’t ready for this drastic option.
Best Herbicide to Kill Poa Annua
The options for homeowners wanting to use a post-emergent selective herbicide to kill Poa Annua without harming their lawn are limited.
But the one herbicide I’ve seen work pretty well is Blindside, which is available from DoMyOwn and on Amazon, though there are 30 states where it cannot be sold or shipped to consumers at the moment, so you may be out of luck.
It’s expensive, and you’ll want to purchase surfactant, dye, and a good sprayer to apply it … making sure to wear all recommended PPE and observing all cautions from the manufacturer.
If you choose to use this (or any other) kind of chemical herbicide, remember to read and follow all the product instructions, wear appropriate personal protective equipment, and to choose a calm day to apply the product.
And whenever you use any herbicide, I suggest testing it in a small area that’s inconspicuous before spraying it on your whole lawn.
This will help you understand if it is effective, and if you’ve mixed it improperly and it kills your turfgrass, you only have a small repair ahead of you.
Should You DIY Herbicide Application to Kill Poa Annua?
As long as you follow the product instructions and take precautions to protect yourself (and other people in your household), you can apply herbicides to kill poa annua as a DIY project.
If you feel uncertain, however, you should consider hiring a lawncare professional.
Herbicides aren’t a joke – many can cause serious health issues, and for many homeowners spraying isn’t something they want to do, preferring to take a long-view to getting rid of poa annua, or simply paying a little extra to have a licensed contractor assume the risk that comes with using these products.
Poa Annua Prevention
We’ve all heard the expression, “an ounce of prevention is worth a pound of cure.” That is certainly true when it comes to preventing poa annua.
As I’ll go over in detail in the next section, natural and organic products and methods for lawn care, including simply keeping your lawn lush, thick, and healthy, are important in preventing poa annua from gaining a foothold in your yard.
Natural and Organic Methods of Eliminating Poa Annua
As we mentioned earlier, poa annua isn’t a weed that you can eliminate with natural and organic methods.
An effective preventative measure, however, is simply taking proper care of your lawn, keeping it lush and healthy, with a dense canopy that deprives weeds like Poa of the light needed to germinate and grow.
So, let’s find out what you should do to maintain your lawn’s health, keeping it beautiful and thick, to make it more difficult for weeds (including poa annua) to grow.
Lawn Care Habits that Can Keep Your Lawn Free of Weeds
Keeping your lawn thick, beautiful and healthy will help suppress weed growth.
After all, there is only so much room for plant growth in the ground. When you have a wonderfully thick and lush lawn, it helps to push out any room for weed growth.
When it comes to non-selective natural and organic methods, vinegar and, in some cases, boiling water, may be helpful.
However, be aware that these approaches may kill whatever turfgrass that come in contact with. This is especially true with vinegar.
Applying vinegar to most kinds of turfgrass will probably kill it.
Be aware that poa annua is more likely to grow and become a problem when your soil is too moist. That is just one reason you shouldn’t overwater your lawn.
Of course, your region, the current weather, and the kind of grass you have play part in how much and how often you water.
If you don’t have much information or knowledge on this, ask the experts at a lawncare center.
When you water your lawn, take your time and give your lawn deep hydration.
This weed’s roots are quite shallow, so watering deeply means your turfgrass will get most of the water. Just ensure you don’t do this too frequently.
Increase Your Lawn Grass Height
Even the height at which you cut your lawn is significant when it comes to preventing and fighting poa annua growth.
This weed grows short.
So, go ahead and let your turfgrass grow higher than average, to about three or four inches. It will help combat poa annua growth by depriving it of the sunlight it needs to thrive.
Leaving your turfgrass a little longer means that the poa annua will have more difficulty surviving.
Another note when it comes to mowing: remember, poa annua seedheads tend to be noticeable when you get to mid-spring.
When the poa annua seedheads become visible, change your mowing height to about two inches and attach a bagger on your lawn mower.
When you do this and you cut your lawn, you will cut off the poa annua seedheads and most of them will end up contained in the bag.
Just make sure they don’t get back on your lawn or in your garden, as this will spread the weed.
Always use a fertilizer that is appropriate for your turfgrass species, as well your region and its climate.
As we’ve already discussed, a thick and lush lawn is unlikely to have any kind of weed problem.
Keep your lawn well-fertilized.
Annual Fertilization Plans to Help Prevent Poa Annua
A few of my favorite options for a done-for-you annual fertilization plan to keep your lawn thick and healthy are:
- Sunday Lawn Care – a subscription lawn care plan based on your lawn’s soil profile and local weather data that delivers exactly what you need, when you need it for a thriving lawn. Save 12% with code LAWNCHICK2023.
- Jonathan Green’s New American Lawn Plan – an annual lawn plan that combines weed and feed products and premium fertilizer with products that will improve your soil’s pH and health for a thick, healthy lawn.
- LawnBox – a granular, plant-based organic fertilizer subscription offering from The Andersons (mentioned earlier). Use code LAWNCHICK at checkout and save 10% off any order and 20% off a pre-paid annual subscription (new customers).
As with any kind of fertilizer, make absolutely certain you carefully read and follow the product instructions on the packaging.
In many cases, you’ll want to apply fertilizer every six to eight weeks.
Aeration and De-thatching
No matter what kind of turfgrass you have on your lawn, you should de-thatch and aerate regularly.
Why? Well, not doing those tasks means your turfgrass roots might not get all the nutrients, sunlight, and water they need.
If this happens, your lawn will become unhealthy and there will be a lot more room for weeds (including poa annua) to thrive and become a problem.
What is Aeration & How Can It Help?
Aeration is the process of creating holes in the soil, so that the roots of your turfgrass can get the water, nutrients, and sunlight they need.
This process eases any compaction in the soil.
Compaction is when soil clumps together so much that there isn’t enough room for sunlight, nutrients, and water to get through.
It can also interfere with water drainage, and too much moisture can make it easier for poa annua to grow and spread.
When you aerate, try to penetrate the lawn to as far as three inches into the ground.
There are different kinds of lawn aeration that you can try. The two main methods are spike aeration and core (or plug) aeration.
Spike aeration tends to be easier (but a little less intensive), and you’re just driving spikes through the ground.
In some cases, you may just wear special gardening shoes that have aeration spikes on the bottom.
There are other more effective spike aeration tools, so look into those too if you’re thinking spike aeration is right your lawn.
Core aeration is the more intensive way of aerating your lawn. With core (or plug) aeration, you are pulling out plugs or clumps of land from your lawn.
This creates more space than a spike aerator would in letting more water, nutrition, and sunlight into the ground, making them better able to reach your turfgrass roots.
What is De-Thatching and How Can It Help?
Having thatch on your lawn if a big problem. But what is thatch?
Thatch is a layer of dead and breaking down material that will build up on the surface of the soil, and if it gets too thick, it can block out water, oxygen, and nutrition from getting down the roots of your turfgrass.
If this happens, your turfgrass roots may end up getting suffocated, and this will make them unhealthy or even kill them.
And as we’ve already gone over, unhealthy or dead grass will make it easier for poa annua and other kinds of weeds from spreading over your lawn.
There are different approaches to dethatching your lawn, and the one (or ones) you choose will depend on the severity of your thatch problem, as well as other factors.
If you only have a minor thatch problem or you want to see how much you can do first on your lawn and without equipment, use a rake to scrape away as much of the thatch as you possibly can.
If you know you need to dethatch your whole yard, you’ll either want to rent a tool, or buy an electric dethatcher.
The Dethatcher I Use & Recommend
For lawns up to a half acre there’s one clear choice when it comes to dethatching tools. I recommend The Greenworks 27022 10AMP Electric Dethatcher.
It works really well and will pay for itself after a few uses when compared to renting a power rake.
The Importance of Timing Your Pre-Emergents
Unlike Crabgrass, Poa Annua is a cool season grass that thrives in spring and fall, so the best time to apply these products (as I discussed earlier) is early fall and early spring, though in some locations two fall applications may be required.
Remember, the right time to apply a pre-emergent herbicide always depends on the specific weed and its characteristics.
This certainly applies to poa annua.
Don’t Allow Too Much Shade
Of course, how much sun or shade your lawn should have depends on the species of turfgrass you have.
But it’s important to recognize that poa annua will start becoming more of a problem if you have too much shade on your lawn.
That is why giving your lawn more sun should help to fight poa annua.
Do you need to cut down your beautiful mature trees?
Absolutely not. But consider a process called “limbing up” your trees, which cuts some of the lower branches and raises the canopy enough so morning and afternoon light can reach the grass growing beneath them.
Final Thoughts About Controlling Annual Bluegrass in Lawns
Now that you’ve read this guide to identifying and eliminating the poa annua weed from your lawn, I hope you feel much more confident about and comfortable with your options to kill Poa Annua.
Understanding what you’re dealing with is always the first step to coming up with a plan to address your problem.
No matter which steps you decide to take to control poa annua in your lawn, always carefully read the label and weigh the risk and benefits of using these products in your yard.
This is key to being able to control weeds without damaging your turfgrass, and without putting your pets, children, neighbors, and even yourself at risk.
Want to keep reading? You may be interested in my lawn weed identification guide.