Annual Bluegrass (Poa Annua) Control: How to Get Rid of Annual Bluegrass (Poa Annua)

This page is a general annual bluegrass (poa annua) control guide. By using the products and methods suggested, you will get control of annual bluegrass (poa annua). Follow this guide, use the recommended products, and we guarantee 100% control of annual bluegrass.

In the springtime when you start to work again on your lawn and see the grass growing, it can be an exciting feeling to know that your hard maintenance work is finally paying off. However, sometimes looks can be deceiving, as is the case when annual bluegrass grass shows up uninvited.

Annual bluegrass is an annual weed commonly found in lawns and occasionally in gardens. Also known aspoa annua, this plant is native to Europe but exists worldwide. Controlling annual bluegrass can be tricky, mainly because this weed has the ability to produce one hundred seeds in as little as two months. These seeds can lay dormant for several years before sprouting.

Annual bluegrass is generally an issue in residential yards because of its appearance in hot weather, resulting in brown spots in lawns during the peak of summer. This weed also thrives in cool weather while most lawn grasses are dying, meaning it has the potential to invade a vulnerable lawn.

If you are dealing with annual bluegrass in your yard, our step-by-step DIY treatment guide will show you how to get rid of poa annua quickly while saving money with the help of our professional quality herbicides.

Identification

Because annual bluegrass (poa annua) can be mistaken for other weeds, such as creeping bentgrass, it is important to properly identify this weed to ensure total control. Here are some identifying traits to keep in mind:

• Annual bluegrass is a cool-seasoned annual weed that develops in low-growing clumps or a bunch-type pattern. When mature, they grow up to 6 or 9 inches in height.
• This weed has a tall light-green flattened stem that are bent at the base or mid-section. The stems are often rooted at the lower stem joint. As the weed matures, it will produce white feathery tufted seed heads. 
• Leaf blades are hairless, smooth, and have a rounded slightly pointed, jagged leaf tip.

Reference the image above to make sure the weed you are dealing with is annual bluegrass or Poa Annua.

Inspection

Once you have confirmed that you are dealing with poa annua or annual bluegrass, you can move on to inspection. Determine where the annual bluegrass is thriving and the surrounding conditions that are helping it to thrive so you know where to focus your herbicide application.

Where to Inspect

Annual bluegrass tends to exist in areas with moist or compact soil, and areas that are somewhat shaded. 

Common sites for this weed to grow are lawns, along sidewalks, fields, crops, ornamental landscapes, and other shaded areas. 

What to Look For

Poa Annua is a cool-season annual, meaning its life cycle will start in the late summer or fall when soil temperatures reach about 70 degrees Fahrenheit and end in spring. 

As the annual bluegrass and native turf grow, clumps of annual bluegrass can easily be spotted as different shades of green among the turf. After six to eight weeks, the weeds flower and spread seeds, then die after a period of drought.

Treatment

Be sure that when handling any type of herbicide, you are properly protecting your skin and eyes with safety equipment. Goggles, gloves and love sleeved clothing should suffice. Annual bluegrass germinates in the late fall or early spring, so timing is critical to being able to effectively control it.

Post-emergent herbicides or non-selective herbicides will work best in removing annual bluegrass. Keep in mind that non-selective herbicides will kill all plants it comes into contact with including the desired ones. 

Step 1: Mix Herbicide

Determine how much herbicide to use by measuring the square footage of the treatment area. To do this, measure the length and widht of the treatment area in feet then multiply them together (length X width = square footage). For acreage, take the square footage and divide it by one acre (square footage / 43,560 sq. ft. = acres). 

Blindside Herbicide is a selective post-emergent herbicide that suppress annual bluegrass in cool-seasoned and warm-seasoned turf.

To control annual bluegrass in cool-seasoned turf, use 0.075 - 0.15 oz. of Blindside Herbicide in 0.5 - 4.0 gallons of water per 1,000 sq. ft. 

To control annual bluegrass in warm-seasoned turf, use 0.15 - 0.23 oz. of product in 0.5 - 4.0 gallons of water per 1,000 sq. ft. 

Tolerant grasses for Blindside Herbicide include Kentucky Bluegrass, Tall Fescue, Bermudagrass, Centipedegrass, St Augustine grass, and Zoysiagrass. 

Keep in mind that this product may not completely eliminate annual bluegrass, which may require a non-selective herbicide like Eraser 41% Glyphosate to be used. 

For spot applications with Eraser 41% Glyphosate, use 2 1/2 oz. (5 Tbs) of product in 1 gallon of water to treat an area approximately 300 sq. ft. 

Mix and apply either of these products with a handheld pump sprayer. 

To mix, simply fill it with half the amount of water, add measured amount of herbicide, then pour in the remaining half of water. Close the tank lid and shake until evenly mixed. 

Step 2: Spot Treatment with Herbicide

Once mixed, adjust your sprayer to a fan spray nozzle setting to get a nice fine coating on the annual bluegrass. 

Spray the top and bottom of the weed leaves until wet, but not to the point of runoff. 

These products will work best when the annual bluegrass is young and actively growing. As the weed matures, they will be more resistant to chemicals which may require repeated applications.

If needed, reapply Blindside Herbicide when 14-20 days have passed from the previous application. 

Weeds treated with Eraser 41% Glyphosphate will perish within 2-4 days, but may take 1-2 weeks for complete death to occur. A second application can be made when 4 weeks have passed from the previous application.  

Prevention

Once annual bluegrass has been eliminated from your property, you will need to implement some preventative measures which will ensure that this weed does not return.

• You can prevent annual bluegrass with a pre-emergent like Barricade Pre-Emergent Herbicide Prodiamine Granular. Depending on your turfgrass type, Barricade can be applied at a rate from 1.5 to 4 pounds per 1,000 sq. ft. Measure the square footage of your lawn to determine how much Barricade you will need. Once you have measured and calculated the area, load the appropriate amount of Barricade into a broadcast spreader at the right calibration and apply to your lawn until it is evenly spread. After broadcasting the granules, you should then water in and activate them with at least 0.5 inches of water.
• Addressing areas of compacted soil and making sure the soil is not too wet is important when it comes to lessening the chances of poa annua making a comeback. Also making sure not to mow your grass too low can help.
• Be mindful of how tall your grass is when mowing the lawn. Annual bluegrass can reseed with less than an inch of grass, and surrounding it with taller grass will shorten its chances at surviving.
• Annual bluegrass tends to live around areas where soil is moist and compact. Avoid overwatering your lawn by adjusting irrigation practices to 1 inch once per week. 

Key Takeaways

What is Annual Bluegrass or Poa Annua?

• Annual bluegrass, or poa annua, is a grassy weed that germinates in late summer or early fall and produces seeds in the spring. It can be easily recognized by it's clumping habit and tall tasseled seed stalk. It is known to frustrate yard owners with its persistence

How To Get Rid of Annual Bluegrass or Poa Annua in Your Yard

• If Annual Bluegrass is already established and growing on your lawn, we recommend a post-emergent treatment with Blindside Herbicide or Eraser 41% Glyphosate. 

Preventing Annual Bluegrass (Poa Annua) Reinfestation

• We recommend applying a pre-emergent to your lawn such as Barricade Pre-Emergent Herbicide Prodiamine Granular with a handheld sprayer in the early spring. This will prevent Annual Bluegrass seeds from growing. Proper lawn care maintenance that addresses soil compaction, drainage issues and nitrogen rates will be important to keep your turf strong and choke out Poa Annua.