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THE WEED
STORY
Prepared and presented by
Carla Bucknor
and
Timon Williamson
Principle 1 – What is a weed?What is a Weed ?
•A plant growing out of place?
•An undesirable plant?
•Plant with a negative...
What is Good or Bad about
Weeds?
• Good
– Some indicate soil
nutrient status
– Increase plant
diversity
– Provide good wil...
• PROACTIVE APPROACH
– Manage vs. Control
– Key aspects
• Why weeds grow
• How weeds grow
• Which weeds species are presen...
Life span of weeds
• Annuals
• Produce a seed crop in one year;
• Competitive - succeed in highly unstable
and unpredictab...
Life span of weeds contd.
• Perennials
• Produce seed crop in excess of one year;
focus is to preserve the parent plant an...
Morphology of weeds
• Grasses
– Family Gramineae
• Sedges
– Family Cyperaceae; thin triangular stem,
absence of a ligule
•...
Grass and Grass-like Weed ID
• Key features to look for on
grasses
– ligule
– auricles
– blade/sheath hairs
• Not all feat...
Broadleaf Weed ID
Key features to look
for:
• Leaf arrangement on
stem
– alternate
– opposite
• Leaf and/or cotyledon
shap...
Broadleaf Weed ID contd.
• Leaf arrangement
on stem
–alternate
–opposite
Leaf arrangement
Alternate – leaves emerge at dif...
Broadleaf Weed ID contd.
•Leaf and/or cotyledon
shape
•Cotyledons or “seed
leaves” emerge first and
are always opposite. D...
Broadleaf Weed ID contd.
Various
leaf
margins
and
shapes
Note toothed
leaf margin
PerennialJohnson grass
(Sorghum halepense)
• Key features
– Membranous ligule
– Prominent midrib
– Reddish-brown seed
– Rh...
PerennialNutsedge (Cyperus)
• Key features
– No ligule
– Triangular stem
– Shiny blades
– Nutlets
• Lifecycle
– Perennial
AnnualJimsonweed
(Datura stramonium)
• Key features
– Long lanceolate
cotyledons with
prominent midrib
– Smooth, lanceolat...
Why and where weeds grow?
• ‘Nature’s means of restoring stability by
protecting bare soils and increasing
biodiversity’
•...
Activation – several days to
50-80 years
Infestation develops over a period
of several years
120 days
Timeline for a typic...
The End
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Weeds

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IDENTIFICATION OF WEEDS

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Weeds

  1. 1. THE WEED STORY Prepared and presented by Carla Bucknor and Timon Williamson
  2. 2. Principle 1 – What is a weed?What is a Weed ? •A plant growing out of place? •An undesirable plant? •Plant with a negative value? •A pest? •A plant that competes with other plants and man for soil?
  3. 3. What is Good or Bad about Weeds? • Good – Some indicate soil nutrient status – Increase plant diversity – Provide good wild life habitat • Bad – Compete with cultivated crops causing yield losses – Out compete native plants – Habitat for insect pests and vectors
  4. 4. • PROACTIVE APPROACH – Manage vs. Control – Key aspects • Why weeds grow • How weeds grow • Which weeds species are present WEED MANAGEMENT
  5. 5. Life span of weeds • Annuals • Produce a seed crop in one year; • Competitive - succeed in highly unstable and unpredictable environments (frequent tillage, drought etc.) as they must make a seed crop before the next disturbance; • Seed dormancy • Long lived seed • Yield more seed than perennials
  6. 6. Life span of weeds contd. • Perennials • Produce seed crop in excess of one year; focus is to preserve the parent plant and produce seed for future generations • Competitive - more stable environs • Perennating parts – stolons, bulbs, tubers, rhizomes • Storage parts – Perennating parts serve as stored food reserves for rapid re growth
  7. 7. Morphology of weeds • Grasses – Family Gramineae • Sedges – Family Cyperaceae; thin triangular stem, absence of a ligule • Broadleaves – Other families of Monocotyledonae and Dicotyledonae; fully expanded broad leaves
  8. 8. Grass and Grass-like Weed ID • Key features to look for on grasses – ligule – auricles – blade/sheath hairs • Not all features will be present • Most ID keys begin with the type of ligule No ligule present Auricles and liguleMembranous ligule Hair-like ligule Collar region Ligule
  9. 9. Broadleaf Weed ID Key features to look for: • Leaf arrangement on stem – alternate – opposite • Leaf and/or cotyledon shape • Other features to consider: – leaf margin traits – leaf texture/hairs – odor • Most seedling keys begin by asking for leaf arrangement, then leaf shape
  10. 10. Broadleaf Weed ID contd. • Leaf arrangement on stem –alternate –opposite Leaf arrangement Alternate – leaves emerge at different points or times on the stem; older ones are larger. Opposite – leaves emerge at the same point and time and are the same size.
  11. 11. Broadleaf Weed ID contd. •Leaf and/or cotyledon shape •Cotyledons or “seed leaves” emerge first and are always opposite. Do not confuse them with the first true leaves, which are used to determine leaf shape on most ID keys.Cotyledons First true leaves
  12. 12. Broadleaf Weed ID contd. Various leaf margins and shapes Note toothed leaf margin
  13. 13. PerennialJohnson grass (Sorghum halepense) • Key features – Membranous ligule – Prominent midrib – Reddish-brown seed – Rhizomes • Lifecycle – Perennial Rhizome with new shoot
  14. 14. PerennialNutsedge (Cyperus) • Key features – No ligule – Triangular stem – Shiny blades – Nutlets • Lifecycle – Perennial
  15. 15. AnnualJimsonweed (Datura stramonium) • Key features – Long lanceolate cotyledons with prominent midrib – Smooth, lanceolate /elliptic true leaves – Purple stems – Odor when crushed – Large white/purple trumpet-shaped flowers – Egg-shaped seed pod with spines • Lifecycle – Summer annual
  16. 16. Why and where weeds grow? • ‘Nature’s means of restoring stability by protecting bare soils and increasing biodiversity’ • Succession –‘The cycle of a natural progression of different plant and animal species over time’.
  17. 17. Activation – several days to 50-80 years Infestation develops over a period of several years 120 days Timeline for a typical weed infestation This shows that weed management CANNOT be done in ONE YEAR
  18. 18. The End

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