Crabgrass is Coming! Along with Goosegrass, Annual Ryegrass, Annual Foxtailgrass, and Poa Annua

April 24, 2024

Maintaining a lush, green lawn is the dream of every homeowner and turf manager. However, this dream can be challenged by the invasion of annual grasses, which can quickly take over and disrupt the beauty and health of turf grass. Among the most notorious invaders are crabgrass, annual goosegrass, annual ryegrass, and annual foxtailgrass. Understanding their characteristics and implementing effective management strategies is crucial to preserving the integrity of turf areas.

Crabgrass (Digitaria sanguinalis):

Annual crabgrass with grass stems that project parallel with the ground, with wide rounded grass blades growing off of the stems

Crabgrass is perhaps the most well-known and widespread annual grass invader. Its low-growing, sprawling habit allows it to outcompete desirable turf grasses, especially in areas with poor soil fertility or inadequate irrigation. Crabgrass thrives in warm climates and germinates from seed each spring, rapidly spreading through prolific seed production. Its presence can be particularly problematic in lawns, golf courses, and athletic fields.

Crabgrass Management Strategies:

  1. Pre-Emergent Herbicides: Applying pre-emergent herbicides in early spring before crabgrass seeds germinate is an effective preventive measure.
  2. Proper Lawn Care: Promoting dense turf through proper mowing, watering, and fertilization can help minimize crabgrass invasion by depriving it of space and resources.
  3. Post-Emergent Herbicides: Selective herbicides can be used to control crabgrass after it has germinated, although timing is critical for optimal effectiveness.
  4. Hand Removal: In small infestations, manually pulling out crabgrass plants can be an environmentally friendly control method.

Annual Goosegrass (Eleusine indica):

Annual goosegrass with thick stems that project outward from a center stock that has broad, thick grass blades growing from the stems

Annual goosegrass, also known as wiregrass, is another troublesome annual grass species commonly found in turf areas. It forms dense clumps and has a distinctive whitish inflorescence. Goosegrass is highly adaptable and can tolerate a wide range of environmental conditions, including compacted soils and low mowing heights.

Goosegrass Management Strategies:

  1. Herbicide Applications: Similar to crabgrass, pre-emergent and post-emergent herbicides are effective for controlling goosegrass. However, multiple applications may be necessary due to its prolonged germination period.
  2. Cultural Practices: Improving soil drainage and reducing compaction can help discourage goosegrass establishment, as it prefers moist, compacted soils.
  3. Vigilant Monitoring: Regular scouting for goosegrass patches allows for early detection and targeted management efforts before infestations become severe.

Annual Ryegrass (Lolium multiflorum)

Patch of annual ryegrass in perennial kentucky bluegrass turf

Annual ryegrass is often used as a temporary winter cover crop or overseeding option in turf management. However, if not properly managed, it can become a nuisance weed, competing with desirable grass species during the growing season. Annual ryegrass has a rapid growth rate and can quickly dominate turf areas if left unchecked.

Annual Ryegrass Management Strategies:

  1. Timely Removal: Overseeded ryegrass should be mowed and removed before it produces viable seeds to prevent its spread.
  2. Herbicide Control: Selective herbicides targeting annual ryegrass can be applied in the spring or fall to suppress its growth and prevent seed production.
  3. Overseeding Alternatives: Consider using alternative cool-season grass species for overseeding that are less invasive and easier to manage.

Annual Foxtailgrass (Setaria spp.):

Green foxtail grass with roots against black background.

Annual foxtailgrass, also known simply as foxtail, is characterized by its bushy seed heads resembling fox tails. It commonly infests lawns, roadsides, and disturbed areas, thriving in sunny, well-drained soils. Foxtailgrass seeds remain viable in the soil for several years, making long-term management essential for control.

Foxtailgrass Management Strategies:

  1. Regular Mowing: Maintaining a regular mowing schedule can prevent foxtailgrass from producing seed heads and reduce its spread.
  2. Herbicide Treatments: Post-emergent herbicides targeting annual grasses can be effective against foxtailgrass when applied during its active growth phase.
  3. Seed Bank Management: Implementing cultural practices that disturb the soil, such as core aeration, can help deplete the foxtailgrass seed bank over time.

Poa Annua (Annual Bluegrass):

Poa annau, annual bluegrass, growing in a small tuft within perennial kentucky bluegrass

Poa annua, or annual bluegrass, is a common weed in turfgrass areas worldwide. It forms dense patches and is often a nuisance due to its light green color and rapid seed production. Annual bluegrass thrives in moist, shaded environments but can also tolerate a wide range of conditions, making it difficult to control.

Management Strategies for Poa Annua:

  1. Herbicide Applications: Selective herbicides targeting annual bluegrass can be applied in the fall or early spring to prevent seed germination and control existing plants.
  2. Cultural Practices: Improving soil drainage and reducing shade can help discourage poa annua establishment in turf areas.
  3. Overseeding with Competitive Grasses: Overseeding with desirable turf grass species that outcompete poa annua can help reduce its presence over time.

Conclusion: Annual grass invaders pose a significant challenge to turfgrass management, requiring a multifaceted approach for effective control. By understanding the characteristics and growth habits of crabgrass, goosegrass, ryegrass, and foxtailgrass, turf managers can implement targeted management strategies to minimize their impact and preserve the health and aesthetics of turf areas. Integrating cultural practices, herbicide applications, and vigilant monitoring is essential for successfully combating these persistent weeds and maintaining vibrant, weed-free lawns and landscapes.