How to Get Rid of POA (Annual Bluegrass)

Identify POA (Annual Bluegrass)

Make sure you are actually looking at POA, because it hides in plain sight as just another patch of grass until it gives itself away. Annual bluegrass has a few clear tells that separate it from your lawn.

• Lighter, yellow-green color: it stands out as brighter and paler than the darker green of your lawn, especially in patches.
• Ugly white seedheads: the dead giveaway. In spring, POA throws up a mass of whitish seedheads, even when mowed low, giving the lawn a speckled, unkempt look.
• Weak, shallow roots: it pulls up easily and forms soft, spongy clumps.
• Dies out in summer: as heat and drought arrive, POA browns and dies, leaving bare or thin spots right when you want your lawn to look its best.

Know the Enemy: Why Timing Beats Everything

POA is beatable, but only if you understand its life cycle, because that is what tells you when to strike. Annual bluegrass is a winter annual: it mostly sprouts from seed in the fall, grows through winter and spring, explodes with seedheads, then dies in summer, dropping thousands of new seeds that wait for next fall. That cycle is the whole key.

• Fall is the main germination window: the bulk of POA germinates in fall as soil temperatures drop below about 70°F. That is your primary target.
• It reseeds prolifically: each plant drops a huge amount of seed before it dies, which is why POA comes back year after year if you do nothing.
• Prevention beats cure: because you cannot easily kill it once it is growing in cool-season turf, stopping the seed from germinating is the winning move.
• Timing is everything: a pre-emergent barrier only works if it is down and active BEFORE the seeds germinate. A day late is a season lost.

Deal With the POA You Already Have

Time for honesty that most lawn sites avoid: there is no cheap, easy way to selectively kill POA in a cool-season lawn. Annual bluegrass is a grass, chemically so similar to your KBG, rye, and fescue that most sprays that hurt it hurt your good grass too. You do have a short ladder of selective options, but they run from gentle-but-weak to strong-but-risky, and none of them is a one-and-done. For most homeowners the realistic playbook is still cultural control plus prevention, with a selective herbicide as a targeted assist. Here is that ladder, honestly.

• Let summer do the work: POA is a winter annual, so it naturally browns and dies in summer heat. If it is spring and you can tolerate the look for a few weeks, nature removes it for you, and your job is just to prevent the next generation.
• Spot-treat heavy patches: for bad clumps, you can spot-spray with a non-selective herbicide, which kills everything it touches including your grass, then rake out the dead material and reseed once it is safe.
• Keep your lawn thick and healthy: dense, well-fed turf mowed at the proper height crowds out POA and gives new seed less room and light to establish.

If you want to chemically target the POA you already have, here are your selective options, from gentlest and safest to strongest and riskiest. All three are legal for a New York homeowner, so the real choice comes down to your grass type, especially whether you have Kentucky bluegrass, and how much fussy timing you are willing to manage.

The Fall Fork: Prevent OR Overseed (Not Both)

This is the decision that trips up almost everyone, so slow down here. A pre-emergent herbicide creates a barrier that stops ALL seeds from germinating, and it cannot tell the difference between POA seed and the grass seed you want to grow. Prodiamine, the backbone of the POA barrier, keeps that barrier active for months and has a reseeding interval of about four months or more.

The problem: the ideal time to lay the fall POA barrier (late August into September) is the exact same window as the best time to overseed a cool-season lawn on Long Island. You cannot do both in the same area the same fall. So you have to choose your priority for this fall.

• Choose PREVENT: lay the fall pre-emergent barrier now to stop POA, and skip fall overseeding. Plan to overseed next fall instead, once the barrier has cleared.
• Choose OVERSEED: overseed this fall to thicken your lawn, and accept that you are not preventing POA this fall. Start the pre-emergent program the following year.
• The one exception: mesotrione (sold as Tenacity) is the only common pre-emergent labeled as safe to use at seeding time, so it is the tool if you must do a little of both, though its POA control is more limited. Verify its label rates separately before using.

Nail the Timing (Soil Temperature and GDD)

A pre-emergent barrier is worthless if it goes down after the seeds have already germinated, so timing is the whole game. Do not go by the calendar alone, because Long Island weather shifts the dates every year. Go by soil temperature and growing degree days (GDD), and use the calendar dates only as a planning framework.

• Fall POA barrier: apply as soil temperatures are dropping toward 70°F, which on Long Island is typically late August into early September. This must be down before the fall POA germination wave.
• Spring barrier: apply as soil warms to about 50°F, or when GDD base 50 (GDD50) reaches about 100, which on Long Island is typically late March into early April. This targets crabgrass and the smaller spring POA flush.
• Measure it: take soil temperature readings at about 4 inches deep in a representative spot (not next to pavement, not in deep shade). A simple soil or meat thermometer works.
• Let the Weather Hub track it for you: the Blade Boss Weather Hub monitors GDD and soil temperature estimates for your exact Long Island location so you can catch the window precisely.

Your POA Prevention Rounds

POA prevention is not a standalone schedule, it is two rounds inside the full Long Island 5-round pre-emergent program. Get these two down on time and you stop the vast majority of annual bluegrass before it ever germinates. The complete program (with the crabgrass rounds too) is laid out in how to prevent weeds.

• Round 5, the fall POA barrier (Aug 25 to Sep 5): prodiamine, applied as soil drops toward 70°F. This is THE round for POA, roughly 80% of it germinates in the fall window once soil falls below 70. It is numbered last only because the program starts in late winter, but it is the single most important round for annual bluegrass. Never miss it.
• Round 1, the late-winter bridge (late Feb to early Mar): pendimethalin, which catches the smaller early-spring POA flush. This is the first round of the year, the program starts here in late winter. It uses pendimethalin (its own separate budget), not prodiamine.
• There is no November round: POA germinates in late summer as soil drops below 70°F, so by November it has already sprouted and a barrier does nothing. Fall means late August, not November.
• Dimension is not a POA tool: dithiopyr has zero post-emergent activity on POA and is commercial-applicator-only in New York. It is held in reserve for crabgrass only. Do not build your POA plan around it.
• Match the rate to your grass type: prodiamine's annual cap is 0.42 oz for fine fescue, 0.55 for KBG/rye, and 0.83 for tall fescue per 1,000. See the full program for the exact per-round rates in each lane.

Apply, Water In, and Hold the Barrier

The barrier only works if you apply it evenly, activate it, and then leave it undisturbed. Granular prodiamine on a spreader is the easiest route for beginners, while the sprayable WDG gives more precise rate control. Whichever you use, the follow-through is the same.

• Spread it evenly: calibrate your spreader and apply in two directions for even coverage. Uneven application leaves gaps POA sneaks through.
• Water it in within 2 to 7 days: apply about half an inch of water to move the herbicide into the top layer of soil and activate the barrier. If rain is coming, let it do the work.
• Do not disturb the barrier: no aeration, dethatching, or hard raking after applying, since breaking the soil surface breaks the chemical barrier and opens the door for POA.
• Stay on schedule: reapply per the program above to keep the barrier active across the season, and remember this is a multi-year commitment to truly beat POA.