What is Annual Bluegrass?

Annual bluegrass, scientifically known as Poa annua, is a common weed that is found in lawns, golf courses, and other turf areas. It is a cool-season grass that thrives in moist and shady conditions, making it a common nuisance in many regions. Despite its name, annual bluegrass can actually be a perennial in certain climates, persisting year after year.


Annual bluegrass can be identified by its bright green color and fine texture. It has a shallow root system and forms dense mats, which can quickly overtake desirable turfgrass species. The leaves are narrow and boat-shaped, with a prominent midvein. The seedheads are small and inconspicuous, often going unnoticed until they produce seeds and spread the weed further.

Life Cycle

Annual bluegrass is an annual weed, meaning it completes its life cycle in one year. It typically germinates in the fall or early spring when soil temperatures are cool and moisture is available. The weed produces seeds prolifically, with each plant capable of producing thousands of seeds. These seeds can remain dormant in the soil for several years, germinating when conditions are favorable.

Growth Habits

Annual bluegrass has a prostrate growth habit, meaning it grows close to the ground and spreads horizontally. It forms dense patches that can quickly crowd out desirable turfgrass species. The weed is well-adapted to shady conditions and can tolerate low mowing heights, making it difficult to control in lawns and golf courses.

Impact on Turfgrass

Annual bluegrass is considered a weed in turfgrass because it competes with desirable grass species for nutrients, water, and sunlight. Its shallow root system and dense growth habit make it particularly effective at outcompeting other plants. The weed can also create an uneven playing surface on golf courses and detract from the overall appearance of lawns.

Control Methods

Controlling annual bluegrass can be challenging due to its prolific seed production and ability to adapt to various growing conditions. Integrated pest management (IPM) practices are often recommended, which include cultural, mechanical, and chemical control methods. Cultural practices such as proper mowing, watering, and fertilization can help promote a healthy turfgrass stand that is more resistant to weed invasion.

Mechanical Control

Mechanical control methods for annual bluegrass include hand-pulling, dethatching, and overseeding. Hand-pulling can be effective for small infestations, but it is labor-intensive and may not be practical for larger areas. Dethatching, or removing the layer of dead grass and debris that accumulates on the soil surface, can help reduce the weed’s presence. Overseeding with desirable turfgrass species can also help fill in bare areas and compete with annual bluegrass.

Chemical Control

Chemical control methods for annual bluegrass typically involve the use of herbicides. Pre-emergent herbicides can be applied before the weed germinates to prevent its establishment. Post-emergent herbicides are used to control existing plants. It is important to carefully follow label instructions and use herbicides that are labeled for use on turfgrass. Additionally, herbicides should be used as part of an overall integrated pest management strategy and not as the sole method of control.


Preventing the establishment of annual bluegrass is key to its control. This can be achieved through proper lawn care practices, such as regular mowing at the appropriate height, adequate watering, and timely fertilization. Avoiding overwatering and excessive fertilization can help create conditions that are less favorable for the weed’s growth. Additionally, maintaining a dense and healthy turfgrass stand can help prevent annual bluegrass from taking hold.


In conclusion, annual bluegrass is a common weed that can be a nuisance in lawns, golf courses, and other turf areas. Its ability to adapt to various growing conditions and prolific seed production make it a challenging weed to control. However, with proper lawn care practices and the use of integrated pest management strategies, it is possible to manage and minimize the presence of annual bluegrass in turfgrass.