Every homeowner hates weeds and wants to stop them appearing in their lawn. But if you don’t know the names and characteristics of the different lawn weeds that may appear, it’ll be difficult to get rid of them. In my experience every weed is a little bit different, and to properly address it you need to identify what it is, and understand its growth and reproduction characteristics to properly remediate it. Today, I’ll compare poa trivialis vs poa annua to explain the differences between these two common (and difficult) weeds.
I’ll help you identify which one you’ve got, and I’ll give you a game plan for how to eliminate each type of “poa” from your lawn.
Poa annua and poa trivialis are both grassy weeds, but there are differences between them (both in terms of how they look, and in terms of how they grow).
Let’s dive into our exploration of these unwanted plants that all too commonly appear on American lawns.
Poa Annua vs Poa Trivialis
Both Poa Annua and Poa Trivialis are types of grass that many homeowners find undesirable (because they look different from most desirable turfgrasses we want in our lawn).
The main difference between poa trivialis and poa annua is that the former (poa trivialis) is a perennial weed (meaning it will return year after year), and the latter (poa annua) is an annual weed (meaning it will die back and return via seeds that it drops in your lawn).
As a cool-season perennial grass, poa trivialis will die back in the heat of the summer but then rejuvenate when the weather becomes more favorable.
An annual is a plant that only lives for one season, and this applies to poa annua.
Beyond the differences in their life-cycle, there are also significant differences between poa annua and poa trivialis from an appearance standpoint.
Understanding these differences will help you correctly identify these weeds and know how to treat them.
After all, you must know which weed you’re dealing with in order to give it the right treatment for elimination and control.
What works for one won’t work for the other.
Let’s Start with Poa Trivialis
As we touched on earlier, poa trivialis is a perennial weed (and grass). You’ll find it at its most visible in the spring and fall months, as it thrives in cooler temperatures.
Lawns with a lot of shade are likely to end up with a poa trivialis problem.
You’ll sometimes hear people call poa trivialis “rough bluegrass.” Sometimes you’ll even hear lawn care experts use this terminology.
Poa trivialis stands out and can usually be identified by its light green color. If you have poa trivialis in your lawn, it will stay alive and come back in subsequent years.
This is because it’s a perennial plant. When it comes to identifying poa trivialis, one of the things to look for is areas of grass that are a lighter green in color than your turfgrass, but the grass will be closer in its growth habit to that of the surrounding turfgrass than Poa Annua (which will develop seedheads sooner).
If your turfgrass is one of the dark green varieties, poa trivialis will be especially obvious, as in the photo above.
Identifying Poa Triv in Summer (cool season lawns)
Have you noticed any inexplicable bare spots on your lawn in the summer heat? This may be a result of poa trivialis.
That is because during the hot weather, poa trivialis enters dormancy and when it does so, it dies back so thoroughly that you can’t see any sign of it.
As poa trivialis is a cool-season grass, it is prevalent in northern areas of the United States. So while you’ll notice the light green color when it’s growing in the fall and spring, during the summer when your lawn may be able to tolerate the heat and drought, the Poa Triv won’t be able to, and it will go dormant and leave thin and bare patches.
More Details about Poa Trivialis
The leaves of poa trivialis are shaped like a boat or canoe, which is another way to help to identify it and pick it out from traditional turfgrass and some other types of grassy weeds.
Also, Poa trivialis tends to become a problem in areas of lawn that have a lot of shade or that are too moist (lack good drainage).
Poa Annua – The Annual Intruder
As implied by its name, poa annua is an annual weed. You’ll sometimes hear people call it “annual bluegrass.”
But unlike the popular Kentucky Bluegrass we all know and love, “annual bluegrass” is a weed.
When it comes to appearance, this annual weed has many similarities to poa trivialis. It is also light green in color, and a grassy weed.
How I Tell Homeowners to Properly Identify Their Bluegrass Weed
In my experience the easiest way for homeowners to differentiate the two is tied to how they reproduce.
As an annual weed, Poa Annua needs to produce seeds (and lots of them) to survive and thrive. As a result it makes seedheads more often and faster.
- If you see a light green grassy weed in your lawn but it’s growing similarly to your perennial turfgrass in your lawn, then it’s probably the perennial Poa Trivialis.
- If you see a light green grassy weed in your lawn, but it’s regularly developing seed heads if you don’t mow frequently, then it’s probably Poa Annua.
Another Tip for Identifying Poa Annua vs Poa Trivialis
Another thing to note as a difference that can help you properly identify if you have Poa Annua vs Poa Trivialis in your lawn is the leaves.
Poa annua leaves often have the same shape (like a boat) as poa trivialis, but they’re a bit more textured. This makes it more noticeable.
Poa Trivialis and Poa Annua Spread Differently
Both poa trivialis and poa annua spread into and throughout your lawn in different ways.
- Poa annua spreads via seed (as mentioned).
- Poa trivialis, by contrast, spreads via stolons.
This last point on Poa Trivialis is important and deserves a little more attention.
I hear from quite a few homeowners with Kentucky Bluegrass lawns, and they mis-identify their Poa Trivialis weed issue as simply a disease problem with their turf.
Here’s how to tell the difference between Poa Trivialis and diseased Kentucky Bluegrass
A closer look at how each type of grass spreads laterally will help you properly identify what is going on.
Kentucky Bluegrass spreads laterally via Rhizomes (underground runners). Rough Bluegrass (or Poa Trivialis) spreads via stolons, which are lateral shoots that travel above the soil.
How to Get Rid of Poa Trivialis and Poa Annua
As there are significant differences between poa trivialis and poa annua, there are also differences in the best approaches for eliminating these weed grasses from your lawn.
And their close relation to popular turfgrass varieties (like Kentucky Bluegrass) makes selection and use of herbicides a challenge.
It’s important that you treat your weed issue carefully, as you don’t want to hurt your turfgrass while getting rid of these grassy weeds.
Getting Rid of Poa Trivialis
Do you have poa trivilias on your lawn? You’ve got to get rid of it and prevent it from reappearing next year.
I like to say that the best defense against difficult weeds like Poa Triv is a good offense.
As with other weeds, keeping your lawn healthy and lush will help crowd out the poa trivialis (“rough bluegrass”) weed, and can help prevent it from being an issue in the first place.
The Lawn Chick editorial team regularly interviews industry experts to bring our readers the latest science and expert recommendations to complement our own hands-on lawn care experience.
We Asked: Why is maintaining a thick, healthy lawn one of the best ways to prevent weeds naturally?
Will Answered: “By maintaining a thick lawn, you’ll be able to limit the amount of ground available for these weeds to take hold, all while promoting the lawn of your dreams and avoiding unnecessary harsh chemicals or preventative herbicide applications.”
Expert Lawn Advisor at Sunday
Born and raised just south of Buffalo, NY, it has been quite a journey for Will getting to explore warm-season grasses after having a hodgepodge of fescue, bluegrass and rye in his lawn growing up. Will graduated from Cornell with a B.S. in Environmental and Sustainability Sciences, with a concentration in Land, Air and Water Resources.
Cool, But I Already Have a Poa Triv Problem – How Do I Fix it?
As poa trivialis is such a stubborn weed, you will probably have to use a non-selective herbicide.
This means an herbicide so strong that it will kill any plant, including your Turfgrass. Once your lawn dies, you can start over.
This is challenging for homeowners, because if you’re not precise enough with application (or if you have rampant Poa Triv issues), you may kill large areas of your lawn.
In fact, it’s so likely that you’ll damage at least some of the turfgrass, you should be ready to replant parts of your lawn, or maybe even all of it.
When people first think of a non-selective herbicide to use to combat Poa Trivialis they’ll think of Roundup. But let’s be real – if you haven’t already associated Roundup (Glyphosate) with cancer, you soon will.
That’s why I prefer either using a strong herbicidal vinegar (not your everyday household kind – I like this one on Amazon), or a herbicidal soap from Sunday called Weed Warrior (my readers can take 15% off with code LAWNCHICK2024).
Whatever you use (even natural products), spray on a calm day, and wear full PPE (long sleeves, closed shoes, gloves, eye protection, and a good mask or respirator).
Preventing Poa Trivialis
You should use cultural controls (including lawncare for a lush and healthy lawn) to help prevent poa trivialis becoming a problem on your lawn.
Even if you already have a limited amount of this weed on your lawn, taking proper care of your lawn and changing the conditions will help to fight it without herbicide.
You can also use pre-emergent herbicides, to help prevent poa trivialis problems in your lawn. But again, make sure you read the instructions and know whether it is a selective or non-selective herbicide.
Here are useful tips for stopping poa trivialis from growing on your lawn.
Like poa annua, poa trivialis prefers moist areas, especially excessively moist areas of soil. So, make sure that you give your lawn the right amount of water, never too much. Don’t mow too frequently.
When you do water your turfgrass, however, water it deeply. Provide enough water so that it soaks down about two inches into the soil.
After watering, leave your lawn enough days for the top layer of soil to dry out. Once this happens, water it again.
This is a great way to avoid overwatering.
At the same time, you’ve got to make sure that you don’t deprive your turfgrass of the water it needs.
Different kinds of turfgrass need different levels of watering. Find out which grass species you have and how much water it needs.
You should also consider your region’s climate and weather. If there is drought, for example, your lawn will need more water.
Overseed Your Lawn Annually
Overseeding with bunchgrasses can help to crowd out poa trivialis. Do this in the spring months to enjoy the intended effect.
Also, aeration and overseeding every year will help to keep your turfgrass healthy, helping to keep out weed growth.
Getting Rid of Poa Annua
Many homeowners use pre-emergent herbicides to fight their poa annua problem, but you will have to select the right product and you’ll probably need to apply it twice a year (in the spring and in the fall) at first.
This is because for pre-emergent to be effective, you need to apply it before any poa annua seeds already in your lawn’s soil is expected to germinate.
Poa annua germination happens when the soil is cooler than 70 degrees Fahrenheit.
Read the instructions on the packaging, to ensure you are using it correctly.
If you’re concerned about applying herbicides to your lawn regularly, you can try an organic, corn gluten meal based product instead.
The Organic Pre-Emergent I Recommend
Want to block weeds without the nasty chemicals? Try Weed Wipeout from Lawnbright.
This natural product is easy to apply with the included hose-end sprayer, and is made with liquid corn gluten meal – an effective pre-emergent herbicide that is USDA National Organic Program compliant and safer for kids and pets than traditional pre-emergent herbicides.
Preventing Poa Annua
Use the same lawncare steps we talked about earlier to help prevent poa annua on your lawn.
Of all the lawncare tips we provide here at Lawn Chick, adjusting your mower deck height to a higher setting (in terms of grass height) may help the most as a natural way to combat weeds like Poa Annua.
I have a tall fescue lawn, and typically maintain a height of three or four inches. This improves the health of my lawn, but also shades out annual weed seeds that need light to germinate and grow.
Of course, you should also fertilize your lawn and keep it healthy and thick.
This combination of dense, tall grass is the most effective (and cost effective) way to combat annual weeds in my experience as a homeowner and full time lawn care blogger.
Remember, a lush, beautiful lawn is one of the most powerful tools for fighting weed growth. Making a lawn fertilization schedule isn’t about vanity or showing off, it’s just one of the most cost-effective ways of taking care of your yard (and preventing headaches in the long run).
Grab my free cheat-sheet if you’d like a ready-to-use gameplan.
Comparison Summary – Poa Trivialis vs Poa Annua
The reality is that poa trivialis and poa annua are extremely similar, and because of their names, some of the information provided online about them is confusing (and some people mix them up).
Here’s a summary of the key points covered in today’s article:
Key Differences and Identification Tips
- One of the main differences between these plants is the fact that poa trivialis is a perennial weed and poa annua is an annual weed.
- To tell the difference between the two you’ll want to look at seed head development (Poa Annua develops seed heads rapidly and constantly since it’s how it survives).
- The leaf shape is similar on both plants, but Poa Annua leaves have more texture.
- You can tell Poa Trivialis apart from Kentucky Bluegrass because it is a light green color, goes brown and dormant in summer, and spreads via stolons (compared to rhizomes with KBG).
How to Prevent & Treat Poa Annua & Poa Trivialis
Regular and well-timed pre-emergent herbicide applications are important to prevent both Poa Trivialis and Poa Annua.
- You can get your Poa Annua under control within a year or two with 2x annual pre-emergent applications, but if you want an immediate fix, your best bet is an herbicide called Blindside (available on DoMyOwn or on Amazon). It can’t be shipped everywhere, though, so it won’t work for everyone.
- You can prevent Poa Trivialis with annual applications of pre-emergent, but to kill it in your lawn you’ll have to use a non-selective herbicide that will kill the surrounding grass as well. I recommend Weed Warrior, a natural herbicidal soap from Sunday (save 15% with code LAWNCHICK2024) instead of Glyphosate for health and safety reasons.
With either weed, you don’t want to put off dealing with your weed problem. The more you procrastinate, the more difficult the problem will be to deal with.
These are both tough lawn weeds.
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