Winter grass, or otherwise known as Poa annua, is an invasive species of weed that grows during winter. Unlike other grasses on your lawn that go dormant and turn brown during winter, this type of grass thrives in cool temperatures. If left unchecked, it can grow out of control and take over your lawn in as little as two years. The good news is that you can learn how to kill winter grass and keep your lawn looking great all year long.
Winter grass can be killed by applying powerful herbicides to it. You can choose pre-emergent herbicides to kill the seeds before they germinate. In the case of a fully-grown plant, post-emergent herbicides are preferred, but they should be applied before the plant matures and begins to seed.
However, it is crucial to learn which ingredients in the herbicides could be fatal to the grass you actually want growing in your lawn. To learn more about those, as well as a few other safe winter grass elimination methods, read on.
How to Get Rid of Winter Grass
Learning about winter grass will help you to understand what you’re dealing with.
First of all, the reason it’s called winter grass is because the seeds germinate in the winter.
If you are not sure what’s growing in your lawn, I have a handy video at the bottom of this post that will help you to determine whether or not it’s winter grass.
If you’ve just realized you do have winter grass in your lawn, killing an already-seeded plant might help to get rid of this problem temporarily, but the seeds will germinate the following winter, which will force you to start the process all over again.
Fully-grown winter grass can produce 1,000’s of seeds by the time winter is over.
The seeds can also stay dormant underground for many years, waiting for the right conditions to trigger germination.
Burying your lawn with a new layer of soil will only delay the inevitable since once you till the soil, the seeds will be exposed and start to germinate.
You should also know that the seeds need a soil temperature average of around 70 degrees Fahrenheit for germination to occur. This will happen during the fall as summer temperatures cool and the seasons move towards winter.
This is the best time to apply your pre-emergent herbicide in order to kill any Poa annua seeds that start to grow.
It is best to check your local university extension office’s website for current soil temperatures.
How to Get Rid of Winter Grass for Good
Spray them with Herbicides
Herbicides have proven quite helpful in the fight against all sorts of weeds – which is what winter grass really is.
While some weeds only require one application to die off, others like winter grass, require additional effort to eradicate them permanently.
Since they only take a short time to mature and seed, winter grasses have built a reputation of being stubborn and growing back even after treatment with herbicides.
This species of grass can also grow all year round in areas that experience annual cool temperatures – so depending on where you live it could be more than just a seasonal problem.
Try the following herbicides to kill off winter grass from your lawn:
Pre-emergent herbicides work by killing the seeds before they germinate.
Winter grass seeds are known to start their germination process towards the end of fall, just as winter begins. The dropping temperatures heading towards winter act as a catalyst to the seeds that have been sitting dormant for nearly a year.
By mixing the pre-emergent herbicide with the soil, you’ll maximize the chances of contact between the seeds and the grass killer.
Pre-emergent herbicides are designed to stop seeds from germinating. For this reason, avoid seeding your lawn with new grass for a maximum of 4 weeks after spraying pre-emergent herbicides.
A consistent and timely pre-emergent application and strategy is your best approach at controlling poa annua. Every year you properly apply your fall pre-emergent you are on step closer of controlling this season grassy weed.
- Apply this product only in EARLY SPRING and FALL
Post-emergent herbicides work by targeting a fully-grown plant by killing it from top to bottom.
However, it has no effects on the seeds, and it’s best to spray it before the plant matures. The best time to do this is before the creamy white seed heads emerge.
Spot spraying is the best option for using post-emergent herbicides to minimize potential damage to your lawn grass.
Make sure you go for selective grass killers tailored to kill weeds only.
Be aware of glyphosate ingredients as they kill any plant that comes in contact with them.
You can apply glyphosate to individual plants by carefully using a paint brush or cotton swabs. While performing this task be sure to wear proper safety gear and and wear double latex gloves to minimize potential contact with the herbicide.
Note: For effective winter grass control, try using both pre- and post-emergent herbicides on your lawn.
Try Hand-Weeding your Lawn
Hand-weeding may sound exhausting, but you shouldn’t underestimate its effectiveness.
This weed control method is best used when you’re concerned that using herbicides will kill or damage other plants on your lawn.
It’s also perfect for small gardens that have been infested by winter grass. The trick is to catch the grass before it starts to seed.
Since it’s easy to spot winter grass on your lawn, applying the hand-weeding technique seems like a practical approach.
You can use hand-weeding to control winter grass that grows on patios, walkways, and cracks on your wall.
It provides a thorough cleaning of your yard, where 99% of the weeds are killed. If you’re keen enough, you can also collect the winter grass seeds after they have dropped, hence eliminating the weeds problem on your yard for good.
However, this weed control method does have some drawbacks.
For starters, it’s both labor and time-intensive. If the soil surface isn’t moist enough, there are higher chances of the plant breaking when you pull it, leaving the roots firmly intact underground, where they can grow back.
On a positive note poa annua is a clumping grass that is easy to hand pull or be removed by up rooting with a small flat headed screwdriver. Remember it is best to try and remover the entire plant including the roots.
Cut the Grass with a Rotary Mower
If you can’t stand the view of winter grass growing on your lawn, try using a rotary lawn mower to cut it down.
The sucking action of a rotary lawn mower helps to pull the clippings into the bag attached to the mower. As a result, you end up collecting all the cut grass and a majority of the seeds into the bag instead of scattering them across your yard. This will help to significantly reduce the number of winter grass that will grow in your lawn next winter.
Using a rotary lawnmower is only practical if the winter grass infestation has become out of hand and you missed the chance to use pre- and post-emergent herbicides. In the case of a manageable size of winter grass on your lawn, try using a hoe or a hand-held spade to dig them out.
Mow the yard at least twice to make sure you catch all the winter grass and the seeds before the seeds have fallen. Dispatch the waste in a garden bin where it will decompose and die off, instead of the garden bed where the seeds might germinate and start the cycle all over again.
Spray Vinegar Solution on the Winter Grass
Vinegar is a natural weed killer. However, you can’t jus use the stuff in your kitchen pantry.
It should be at least 20% acidic like these options.
Keep in mind that vinegar is a non-selective weed killer and will kill any plant that comes in contact with it. In this case, make sure you apply the spot-spraying technique to protect other plants on your lawn.
As an invasive grass, winter grass can survive and thrive under cold temperatures.
If left unchecked, this winter weed can get out of control, since a single plant can produce approximately 1000 seeds. The seeds can stay dormant underground for a long time as well.
Use both pre- and post-emergent herbicides to control and kill the winter grass. Make sure to use selective herbicides to protect your lawn grass.
You can try home remedies, such as a mixture of vinegar and dishwashing soap, to target the grass before they flower and seed. Keep in mind that vinegar is non-selective and would kill any plants.
Mowing your lawn with a rotary mower is excellent for controlling a full-blown infestation of winter grass. Hand-weeding winter grass is perfect for small gardens, patios, and walkways and effective but time consuming in lawns.
More Lawn Care Advice:
Frequently Asked Questions:
What Does Poa annua (Winter Grass) Look Like?
Should I Pull Poa Annua By Hand?
If you happen to notice that you have just a few small patches of wintergrass starting to grow, you should absolutely pull it out by hand as soon as possible. If you catch it early enough before it matures and drops it’s seeds you will be able to stop it from spreading. Hand pulling is a great method if you catch the problem early enough, but if the plant has grown to the point of dropping seeds you’re going to need to use herbicides to stop it’s progress.
How Long Does it Take to Kill Poa annua?
That depends on how long the plant has been established in your lawn. As mentioned above, if you catch it early enough you if you can pull it before it has dropped any seeds then you will be able to instantly kill it over night just by pulling it by hand.
However, if there are established patches throughout your lawn you can pretty much guarantee that seeds have been dropped and now you have a much longer process on your hands. If you are diligent with your pre and post-emergent herbicide applications and you apply them at the perfect time then you have a good chance of eradicating the problem in about 6 months.
Most homeowners don’t get it exactly right the first time, which means your probably going to need to repeat the entire process a second time to catch anything you missed the first year. Altogether it could take 2 years to completely kill all winter grass in your yard.