Annual Meadow Grass

Annual meadow grass (Poa annua) is found across all soils in Ireland. Perennial meadow grasses like rough-stalked (Poa trivialis) or smooth-stalked meadow (Poa pratensis) grasses are also widespread, especially in grassland, field margins and headlands, but also occur as an in-crop arable weed, mainly where grass seed mixes are used in field margins.

Figure 1. Annual Meadow Grass

Key Features

• Germinates throughout the year, especially in September, due to more reliable soil moisture.
• Under ideal conditions, it can flower and set seeds within six weeks of germination. Several generations per year of annual meadow grass are possible.
• Rough-stalked and smooth-stalked meadow grass germinate mainly in autumn and shed seeds in the following summer.
• Plants can emerge from seeds found within the top 5 cm of soil.
• Individual plants can produce 10,000 to 20,000 seeds.
• There is an annual 45% decline in seed viability.
• Low populations in crop do not reduce crop yield.
• Seed dormancy (>5 years).

Identification

• Bright green leaf blade with boat shaped tip and pale green underside sheath.
• ligule medium (2-5 mm), roundly pointed and serrated.
• Open-branched and spreading seed heads.
• Leaves flattened in shoot.

Figure 2. Annual Meadow Grass Identification