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Weeds What is a weed? A weed is a plant out of place
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What Do Weeds Do? Compete with crops for resources Interfere with crop quality and quantity Reduce aesthetics of landscape Affect function of turfgrass Displace native flora
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Harbor insects and plant pathogens
What Do Weeds Do? Ragweed pollen causes hay fever Cause allergies Harm people Harbor insects and plant pathogens
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Weeds -- How Did They Get There?
Every shovel full of soil contains thousands of weed seeds -- waiting for an opportunity Often we just provide the weeds with the opportunity and environment to flourish
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Weed Seed Are Spread By:
Wind People Rain runoff Birds and other animals Garden cultivation Mowing Topsoil or compost addition Purchased plants
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Invaders - weed dispersal
Wind Surface water Birds & animals Activities of man site prep, cultivation, planting
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How we introduce and move weeds
top soil organic amendments equipment plants
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And, sometimes we intentionally introduce weeds
Multiflora rose Crabgrass Kudzu
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More Plants (weeds) Intentionally Introduced
Water hyacinth Bamboo Japanese knotweed
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The First Step in Weed Management is Identification
The First Step in Weed Management is Identification! Weed Identification – Its More Than Knowing a Name!
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Why is it Important to Identify Weeds?
So you know when it germinates, how it spreads, And, so you can determine the most appropriate control measure(s) -- herbicides, cultivation, mulches, etc.
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How do you correctly identify a weed?
Compare to a photo Remember weeds can appear different due to site conditions Easiest to do when plant is flowering Keys to Identification Send a sample to the local Cooperative Extension office
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Identification Resources
For Piedmont and Coastal Plains Identifying Seedling and Mature Weeds in the Southeastern US Weeds of Southern Turfgrass Mountains Weeds of the Northeast
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Identifying Seedling and Mature Weeds in the Southeastern US (AG-208)
How to order: Identifying Seedling and Mature Weeds in the Southeastern US (AG-208) Publications Office, Box 7603 NCSU, Raleigh, NC $10.00
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How to order: Weeds of Southern Turfgrass
Publication Distributions Center IFAS Building 664 P. O. Box University of Florida Gainesville, FL 32611 ( ) $ $3.00 shipping
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How to order: Weeds of the Northeast Cornell University Press
P. O. Box 6525 Ithaca, NY $29.95 plus $5 shipping
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Some Web-Based Weed ID Resources
axp.ipm.ucdavis.edu/PMG/weeds_common.html
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How to send a sample for ID
Fresh samples: moisten sample; wrap in DRY paper towel; put in a zip-lock bag and mail on Monday or Tuesday to the appropriate specialist
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How to send a sample for ID
If you cannot send it right away (or if you get the sample on Thursday or Friday: Lay flat on between newspaper; press. Mail the dried, pressed sample to the appropriate specialist
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Use the Sample Submission Form
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Classification of Weeds
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Ways weeds are classified
Weed Classification Ways weeds are classified Lifecycle Seed leaves Growth habit Susceptibility to herbicides
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Lifecycles Annual Biennial Perennial
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Life cycle of an annual weed
Plant dies Seed Seedling Plant sets seed Plant flowers
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Life cycle of a winter annual weed
Summer Fall Plant dies Seed Seedling Plant sets seed Plant flowers
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Common winter annual weeds
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Life cycle of a summer annual weed
Spring Fall Plant dies Seed Seedling Plant sets seed Plant flowers
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Common Summer Annual Weeds
J. Derr J. Neal J. Neal J. Neal
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Life cycle of a biennial weed
Plant dies Seedling Seed Second Season First Season Plant sets seed Plant flowers Over-winters as a rosette
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Bull Thistle Queens Ann’s Lace Mullein Common Biennials J. DiTomaso
R. Uva J. Neal
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Life cycle of a perennial weed
Roots/ rhizomes spread Seedling Seed Plant Over-winters Plant Flowers Plant sets Seed New plant
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Some common perennial weeds
R. Uva J. Neal R. Uva J. Neal J. Neal
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Perennial Weeds Reproduce By:
Seeds Tubers Bulbs Rhizomes Stolons
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Types of Perennial Weeds
Simple perennials Creeping perennials Rhizomes Stolons Creeping roots that produce shoots Tuberous perennials Bulbous perennials
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Tap root or hardy fibrous root system
Simple Perennials Spread by seed Tap root or hardy fibrous root system Examples: dandelion, plantain, dogfennel, pokeweed Tap root
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Creeping Perennials Reproduce and spread by
Stolon Reproduce and spread by Underground stems (rhizomes) Above-ground stems (stolons) Creeping fleshy roots that produce new shoots Many also reproduce by seeds or other means. Rhizome
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Tuberous Perennials Tubers are swollen, modified stems that are often resilient to controls, spread by cultivation, and may persist in the soil for years. Tubers form on rhizomes Tubers J. Neal
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Bulbous Perennials Persist through the dormant season as a bulb
Wild garlic and wild onion produce bulblets, aerial bulblets, and seeds R. Uva
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Weeds Are Also Classified By:
Cotyledons (Seed leaves) Dicot (two seed leaves) Monocot (one seed leaf)
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Monocots One seed leaf when plant emerges Long narrow leaves Parallel veins
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Monocots -- Examples Grasses Onions Garlic Sedges Rushes Lilies Dayflower
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Grasses Rounded or flattened stems and nodes Have fibrous root systems
Some have fibrous roots, rhizomes or stolons for reproduction Growing point is below surface
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Grasses are identified by:
seedhead blade Grasses are identified by: sheath ligule auricles midrib collar stolon bud leaf crown rhizome
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Vernation or Leaf Bud Rolled in the bud Folded in the bud
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Ligules Absent Membranous Hairy The Scotts Co. The Scotts Co.
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Ligules Absent Membranous Hairy
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Auricle Absent Present Clasping The Scotts Co. The Scotts Co.
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Seedheads Panicle Branched spike Spike The Scotts Co. The Scotts Co.
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Seedheads Panicle Branched spike Spike
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Grass-Like Weeds Sedges: Sedges have triangular “stems”. Grasses have flat or rounded “stems”. Annual and perennial species Most common and difficult to control are yellow and purple nutsedge Wild Garlic and wild onion: hollow leaves have a pungent onion-like or garlic-like aroma Wild garlic is the most common
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Yellow and Purple Nutsedges (Cyperus spp.)
A. Senesac Yellow and Purple Nutsedges (Cyperus spp.) Grass-like, but “Sedges have edges” – triangular “stems” Leaves emerge 3-ranked Spread by rhizomes and over-winter as tubers Tubers often introduced in top soil J. Neal
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Yellow Nutsedge (Cyperus esculentus)
R. Uva Yellow Nutsedge (Cyperus esculentus) Perennial with rhizomes and tubers Emerge in late spring; die in the fall “Daughter” plants and tubers formed at tips of rhizomes One plant can form as many as 6000 tubers J. Neal
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PurpleNutsedge (Cyperus rotundus)
Rhizomatous and tuberous perennial Emerge in mid-spring; die in the fall Forms tubers within 6 weeks of emergence Very hard to control The “world’s worst weed” J. Neal Forms tubers in “chains” J. Neal
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Yellow vs. Purple – Leaf tips
Yellow nutsedge leaf tips taper to a long, narrow point Purple nutsedge leaf tips are pointed but not tapered Yellow Purple J. Neal
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Yellow vs. Purple -- Flowers
Purple Nutsedge J. Neal Yellow Nutsedge J. Derr Purple or reddish brown turning black Yellow fading to tan
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Wild Garlic (Allium vineale)
R. Uva Wild Garlic (Allium vineale) Bulbous perennial Strong scent Reproduces by bulblets, rarely by seed Emerges in the winter and dies back in late spring or early summer J. Neal Aerial bulblets
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Dicots or Broadleaf weeds
Two seed leaves (cotyledons) Leaves have netted veins Largest group of weeds Often with bright showy flowers Exposed growing points
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Unique Characteristics Growth Habit Leaf Orientation, Shape, Etc.
How to ID Dicots Flowers Unique Characteristics Growth Habit Leaf Orientation, Shape, Etc.
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Unique Characteristics
R. Uva Unique Characteristics Look for: Thorns or spines Square or winged stems Compound leaves Whorled leaves Milky sap
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Growth Habits J. Neal J. Neal Upright Spreading
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Leaf Orientation Opposite Whorled Alternate Rosette
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Simple Verses Compound Leaves
R. Uva J. Derr Pinnate Palmate Simple Compound
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Other Ways to Identify Cont.
Leaf shape Leaf margin Toothed,entire,lobed, or deeply cut Petiole length Hair on leaves or other parts
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Leaf Shapes, tips & bases
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Shallow lobes or toothed
Leaf Margins Deeply lobed Entire Shallow lobes or toothed J. Ditomaso R. Uva
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Hairs – present or absent, & where?
J. Neal J. DiTomaso Mouseear chickweed -- Hairs on stem & leaves Common chickweed -- Hairs absent
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Tell Me What You See?
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Broad, nearly entire leaves 5 veins Flowers on spikes
Tell Me What You See? Rosette Broad, nearly entire leaves 5 veins Flowers on spikes Broadleaf plantain
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Tell Me What You See? L. Clark
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Tell Me What You See? Alternate leaves
L. Clark Alternate leaves Deeply divided (dissected) leaves. Twice lobed.
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