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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