© Hermann Geissel 2004 - Leaving Certificate Agricultural Science - http://www.agscience.ie

Problem Weeds in Cereals

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Reproduced here by kind permission.

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A brief glossary has been added.




Contents:

Loose Silky-bent
Annual Meadow-grass
Black-grass
Wild-oat
Common Chickweed
Scented Mayweed
Common Hemp-nettle
Red Dead-nettle
Knotgrass
Ivy-leaved Speedwell
Field Pansy
Goose-grass (Robin-run-the-hedge, Bedstraw, Cleavers)
GLOSSARY




Loose Silky-bent

  • Name:
    • Loose Silky-bent; Apera spica-venti
  • Family:
    • Gramineae
  • Habitat:
    • Occurs especially on sandy and loamy soils rich in nutrients and low in lime
  • Germination period:
    • Predominantly in the autumn but also in the spring
  • Flowering period:
    • June to early August
  • Characteristics:
    • 20-100 cm in height
    • Ligules 3-10cm, deeply fringed
    • Leaf base without auricles
    • Youngest leaf rolled
    • Leaves non-hairy

Annual Meadow-grass

  • Name:
    • Annual Meadow-grass; Poa annua
  • Family:
    • Gramineae
  • Habitat:
    • Prefers compact sandy loam or pure loam and clay soils well provided with nutrients
  • Germination period:
    • Almost throughout the year
  • Flowering period:
    • Almost throughout the year
  • Characteristics:
    • Up to 30 cm in height
    • Ligules 2-5 mm long, collar-shaped, thinly membranous
    • Leaf base without auricles
    • First leaf folded
    • Leaves non-hairy
    • Lamina along the middle vein with two lengthwise grooves
    • Leaf with boat-shaped tip.

Black-grass

  • Name:
    • Black-grass; Alopecurus myosuroides
  • Family:
    • Gramineae
  • Habitat:
    • Occurs generally on sandy or pure loams rich in nutrients
    • Loam and clay indicator plant
  • Germination period:
    • Autumn to spring
  • Flowering period:
    • May to July
  • Characteristics:
    • 20-80 cm in height
    • Long ligule, generally irregularly dentate
    • Leaf base without auricles
    • First leaf rolled
    • Leaves non-hairy

Wild-oat

  • Name:
    • Wild-oat; Avena fatua
  • Family:
    • Gramineae
  • Habitat:
    • Prefers newly-turned, damp loam and clay soils rich in nutrients
  • Germination period:
    • Predominantly in spring but also in the autumn
  • Flowering period:
    • June to September
  • Characteristics:
    • Up to 150cm in height
    • Ligules up to 6mm long, membranous
    • Leaf base without auricles
    • Youngest leaf rolled
    • Leaf sheath and margins ciliate towards the leaf base, otherwise non-hairy

Common Chickweed

  • Name:
    • Common Chickweed; Stellaria media
  • Family:
    • Caryophyllaceae
  • Habitat:
    • Widespread
    • Encountered especially on humus containing sandy to loamy soils very rich in nutrients
    • Nitrogen indicator plant
  • Germination period:
    • Throughout the year
  • Flowering period:
    • Almost throughout the year
  • Characteristics:
    • 5-30cm in height
    • Generally prostrate and bolster forming
    • Foliage leaves opposite in pairs and pointed to egg-shaped
    • Stem with single line of hair down each internode.

Scented Mayweed

  • Name:
    • Scented Mayweed; Matricaria chamomilla
  • Family:
    • Compositae
  • Habitat:
    • On sandy or pure loam and clay soils, rich in nutrients, varying in humus content and generally low in lime
    • Loam indicator plant
  • Germination period:
    • Autumn to spring
  • Flowering period:
    • May to July (August)
  • Characteristics:
    • Leaves deeply and finely pinnate
    • Stem bare, generally branching

Common Hemp-nettle

  • Name:
    • Common Hemp-nettle; Galeopsis tetrahit
  • Family:
    • Labiatae
  • Habitat:
    • On humus-containing, preferably stony to sandy loams rich in nutrients
  • Germination period:
    • Spring
  • Flowering period:
    • June to October
  • Characteristics:
    • Up to 50 (80) cm in height
    • Foliage leaves longish to eggshaped, pointed at the tip, margin toothed, stalked
    • Stem erect, often branching, smooth, round and distinctly thickened at the nodes

Red Dead-nettle

  • Name:
    • Red Dead-nettle; Lamium purpureum
  • Family:
    • Labiatae
  • Habitat:
    • On newly-turned sandy or pure loam soils rich in nutrients
    • Nitrogen indicator plant
  • Germination period:
    • Throughout the year but mainly in autumn
  • Flowering period:
    • March to September (winter flowering plant)
  • Characteristics:
    • Up to 25cm in height
    • Foliage leaves crosswise opposite, stalked, covered with soft hairs, distinctly veined
    • Stem with square cross-section

Knotgrass

  • Name:
    • Knotgrass; Polygonum aviculare
  • Family:
    • Polygonaceae
  • Habitat:
    • Predominantly on humus-containing sandy and loamy soils rich in nutrients
    • Nitrogen indicator plant
  • Germination period:
    • Spring to early summer
  • Flowering period:
    • June to October
  • Characteristics:
    • Up to 50cm in height
    • Generally prostrate, richly branched, bolster-forming
    • Longish foliage leaves with very short petioles, enveloped at the base of the stalk by a thin, transparent, non-ciliate, slit membrane (leaf sheath of stipule)

Ivy-leaved speedwell

  • Name:
    • Ivy-leaved speedwell; Veronica hederifolia
  • Family:
    • Scrophulariaceae
  • Habitat:
    • Humus-containing, sandy-stony or pure loam soils rich in nutrients
    • Loam indicator plant
  • Germination period:
    • Mainly in autumn but also in spring
  • Flowering period:
    • March to May
  • Characteristics:
    • Up to 30 cm in height
    • Leaves heart to ivy shaped, mostly 3-lobed (sometimes up to 7 lobes), ciliate, stalked
    • Stems prostrate and strongly branched at the base, with scattered hairs

Field pansy

  • Name:
    • Field pansy; Viola arvensis (V. tricolor, subspecies arvensis)
  • Family:
    • Violaceae
  • Habitat:
    • Sandy or loamy soils varying in humus content and rich in nutrients
  • Germination period:
    • Throughout the year but with peaks in the autumn and spring
  • Flowering period:
    • Almost throughout the year but mainly from May to October
  • Characteristics:
    • Up to 30cm in height
    • Foliage leaves sinuate to notched, with slightly wavy margins
    • Leaves narrowing towards the stalk
    • Small stipules at the base of the stalk

Goose-grass

  • Name:
    • Goose-grass (Robin-run-the-hedge, Bedstraw, Cleavers); Galium aparine
  • Family:
    • Rubiaceae
  • Habitat:
    • On sandy or pure loam and clay soils rich in nutrients and humuscontaining
    • Loam and nitrogen indicator plant
  • Germination period:
    • Autumn and winter
  • Flowering period:
    • June to October
  • Characteristics:
    • Up to 120cm in height
    • Spreading climber
    • Leaves longish and pointed and arranged 4-8 in whorls, covered at the edge and on the underside with curved prickles
    • Stem also covered with prickles and square in cross-section

GLOSSARY


© Hermann Geissel 2004 - Leaving Certificate Agricultural Science - http://www.agscience.ie