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Weeds. Category E Turf and Ornamental Pesticide Applicator Training Manual Chapter 4. Introduction. In this chapter you need to understand: Why weeds are important. When a plant is a weed. Damage weeds can cause. Identify some Minnesota plants considered weeds. Terms.

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weeds

Weeds

Category E Turf and Ornamental

Pesticide Applicator Training Manual Chapter 4

introduction
Introduction
  • In this chapter you need to understand:
    • Why weeds are important.
    • When a plant is a weed.
    • Damage weeds can cause.
    • Identify some Minnesota plants considered weeds.
terms
Terms
  • Broadleaf weeds—dicots that are growing where they are not wanted.
  • Grassy weeds—monocots that are growing where they are not wanted.

Category E--- Chapter 4 Weeds

why weeds are important
Why Weeds are Important
  • Weeds:
    • Detract from the appearance of the landscape.
    • Compete with desirable plants for space, nutrients, and water.
    • Can provide habitat for other plant pests.
what s a weed
What’s a Weed?
  • Any unwanted plant.
  • A plant can be invasive into desired plants
    • Some produce large amounts of seed.
    • Some can reproduce vegetatively (roots and stems) through normal cultural practices e.g. Mowing.
    • Legally declared weeds by the State of Minnesota e.g. Canadian thistle or local governments e.g. common buckthorn in Minneapolis
potential damage from weeds
Potential Damage from Weeds
  • Compete with ornaments for water, nutrients, light, and space.
  • Can interfere with management practices e.g. planting, thinning.
  • Some weeds produce substances that inhibit growth of other plants (allopathy).
  • Some weeds produce irritating or poisonous substances.
weed identification
Weed Identification
  • Turfgrass weeds fall into 2 groups:
    • Grassy—monocots (have a single leaf on emergence). Examples: crabgrass, quackgrass, tall fescue.
    • Broadleaf —dicots (have 2 leaves on emergence). Examples: dandelion palntain.
weed identification dandelion
Weed IdentificationDandelion
  • Low-growing perennial.
  • Rosette habit.
  • Thick roots.
  • Plant can regenerate from small root or stem segments.
  • Tiny seeds can disperse great distances.
  • Thrive in weak, thin turf.
weed identification common chickweed
Weed IdentificationCommon Chickweed
  • Creeping annual weed.
  • Small, pale green weeds and petioles.
  • Grows best in cool, wet weather.
  • Shade tolerant.
  • To help prevent—Maintain a dense turf and water infrequently
weed identification crabgrass
Weed IdentificationCrabgrass
  • Coarse blades, light green.
  • Can germinate the entire season after the soil warms.
  • To help prevent—maintain a dense, healthy turf.
  • Apply preemergent after soil reaches 55°F.
weed identification foxtail
Weed IdentificationFoxtail
  • Annual grass, has long hairs on the upper surface of the leaf blade and cylindrical yellow seedheads.
weed identification canada thistle
Weed IdentificationCanada Thistle
  • Perennial weed spread by seeds and creeping roots (can extend up to 20 feet).
  • Large numbers of wind-dispersed seeds.
  • Destroy by digging out roots or some herbicides.
weed identification quackgrass
Weed IdentificationQuackgrass
  • Perennial grass spread by rhizomes.
  • Cannot be controlled with shallow cultivation—requires deep tilling.
weed identification prostrate knotweed
Weed IdentificationProstrate Knotweed
  • Annual, low-growing.
  • Very competitive in compacted ,high traffic, infertile soil.
weed identification prostrate spurge
Weed IdentificationProstrate Spurge
  • Annual, low-growing.
  • Reddish or green prostrate stems.
  • Often found on poorly fertilized soils.
  • To help prevent—maintain a dense, healthy turf.
  • Apply preemergents when soil 60-65°F.
weed identification bindweed
Weed IdentificationBindweed
  • Perennial, vining herb.
  • Extensive root system, hard to control.
  • Pull out or cut root 3-6 inches below the surface.
weed identification purslane
Weed IdentificationPurslane
  • Annual, fibrous root system.
  • Stems smooth, often reddish and prostrate.
  • Common in cultivated areas.
  • Difficult to control with cultivation.
weed identification ground ivy
Weed IdentificationGround Ivy
  • Perennial, creeping growth habit, forms dense patches.
  • Grows well in shady, poorly drained areas.
weed identification white clover
Weed IdentificationWhite Clover
  • Perennial, low-growing.
  • Will root from nodes.
  • Competes effectively with established lawns—especially in moist conditions and low fertility.
herbicides
Herbicides
  • Nonselective herbicide—a chemical that is generally toxic to plants without regard to species….
  • Preemergent—prior to the emergence of the specified weed or crop.
  • Postemergent—after the emergence of the specified weed or crop.

Credit: Ware, G.E. 2000. The Pesticide Book, 5th Edition.