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What makes a plant “weedy”? Top 5 “Weedy” Traits

• #1) Reproductive productivity and flexibility

– High seed or propagule production

– More than one way to reproduce

• Cross pollinated seed

• Self pollinated seed

• Rhizome, bulb, tuber, stolon production

• Aggressive tiller or shoot production

• Ability to sprout roots from cut stem portions

Weeds like crabgrass, goosegrass and annual bluegrass produce 5 to 10 times recommended turfgrass seeding rates each year.

Top 5 “Weedy” Traits

• #2) Highly dispersible

– Seed or other propagules moved by multiple methods

– Able to colonize and invade many sites

Wind Animals Water

Top 5 “Weedy” Traits

• #3) Discontinuous germination or sprouting

– Seed and other structures innately have varying dormancy mechanisms that make sure all new plants do not emerge together. “A family that germinates together, may die together”

This acacia plant germinated from 200 year old seed found in a Dutch merchant’s notebook.

One of these 2000 year old Judean date palm seeds germinated after archeological excavation, possibly renewing an extinct species.

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Top 5 “Weedy” Traits

• #4) Adaptability

– Able to survive extreme conditions and unexpected changes in environment

– Genetic diversity insures the population will persist although many individuals may perish

Prickly lettuce in sidewalk crack Curly dock on partially

submerged log Roundup resistant horseweed

Top 5 “Weedy” Traits • #5) Competitive

– “Earliness” allows weeds to get the jump on turf via early germination or fast growth rate in cool weather

– Weeds capture resources such as light, moisture, and nutrients and reduce turf density or plant quality

Dandelion sprouts from a taproot and gains position before bermudagrass breaks dormancy

Dallisgrass punches through zoysiagrass with power from a large rhizome

Competition

• Generally, weeds capture resources efficiently because of the following characteristics

– Early germination

– Rapid seedling growth

– Large leaf area

– Massive root systems

Sowthistle germinated through snow

Massive rhizomes of bahiagrass

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How to Identify Weeds

Tools of the Trade

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Weed Identification

Why is Weed ID Important? • To treat infestations accordingly

– Herbicide application

– Tillage system

– Cropping system selection

• To minimize economic losses

– Early season competition losses

– Additional applications

• To avoid poisonous weeds

– Grazing of livestock

– Weeds hazardous to humans

Alternatives to Becoming a Plant Taxonomist

• Memorize characteristics of key families

• Use the available plant ID materials

– Text books

– CD-based ID databases

– Online resources

• Make some dried mounts

– Quick and easy

– You will likely see the weed again

• Have contacts that can help you

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Weed I.D. Sources

Questions?

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Classification by Plant Family

• Botanist classify plants primarily by floral characteristics

Example: Lamiaceae (Mint Family)

Ground ivy Henbit Lyre leaf sage Purple deadnettle

Annuals

Winter annuals

Summer annuals

Biennials

Perennials

Classification by Life Cycle

Common chickweed

Henbit & deadnettle

Black medic

Bracted plantain

Speedwells

Shepherd’s purse

Mustards

Winter Annual Broadleaves

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Prostrate knotweed

Carpetweed

Common lambsquarters

Common purslane

Bedstraw

Summer Annual Broadleaves

Wild carrot

Carolina geranium

Purple cudweed

Shiny cudweed

Common mullein

Toadflax

Biennial Broadleaves

Dandelion

Plantains

Virginia buttonweed

Ground ivy

Creeping buttercup

Curly dock

Thistles

White clover

Healall

Violets

Perennial Broadleaves

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Annual bluegrass

Barnyardgrass

Goosegrass

Crabgrass

Foxtails

Fall panicum

Annual Grasses

Poa trivialis

Dallisgrass

Johnsongrass

Bermudagrass

Tall Fescue

Nimblewill

Quackgrass

Perennial Grasses

Plant Life Cycle

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Types of Propagules

• Seed – a small embryonic plant enclosed in a covering that is the product of the ripened plant ovule

Field sandbur Common groundsel

Types of Propagules

• Rhizome – underground stem that can emit roots from the lower side and leaves from the upper side

Quackgrass Dallisgrass

Types of Propagules

• Stolon – aboveground stem that can develop new plants by rooting at nodes

Ground ivy Bermudagrass

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Types of Propagules

• Tuber – thickened portions of rhizomes or roots that store carbohydrate for propagation

Yellow nutsedge

Types of Propagules

• Bulb – underground organs for carbohydrate storage on which specialized leaves prominently develop

Wild garlic Star of Bethlehem

Top 7 Broadleaf ID Characteristics

• Cotyledons

• Habit

• Leaf arrangement

• Leaf shape

• Stem

• Hairs

• Bloom

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Broadleaf ID - Cotyledons

Oval Black medic

Oblong Common purslane

Round Field bindweed

Lance Smooth pigweed

Needle Buckhorn plantain

Spoon Mouseear chickweed

Spatula Persian speedwell

Heart/Kidney Wild mustard

Broadleaf ID - Habit

Prostrate Prostrate knotweed

Upright American burnweed

Vine Field bindweed

Broadleaf ID – Leaf Arrangement

Alternate Virginia creeper

Opposite Mouseear chickweed

Rosette Prickly lettuce

Worled Catchweed bedstraw

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Broadleaf ID – Leaf Shape

Oval Common chickweed

Heart Shape Persian speedwell

Lance Shaped Horseweed

Trifoliate White clover

Digitate Virginia creeper

Pinnate Longstalk phyllanthus

Needle Field horsetail

Lobed Hairy bittercress

What leaf shape is this?

What leaf shape is this?

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What leaf shape is this?

What leaf shape is this?

What leaf shape is this?

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What leaf shape is this?

What leaf shape is this?

What leaf shape is this?

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Broadleaf ID - Stem

Round Persian speedwell

Square Henbit

Broadleaf ID – Leaf Margin

Entire Common chickweed

Serrate American burnweed

Crenate Ground ivy

What leaf margin is this?

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What leaf margin is this?

What leaf margin is this?

What leaf margin is this?

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What leaf margin is this?

Broadleaf ID – Flower Symmetry

Actinomorphic Dandelion

Zygomorphic Henbit

What flower symmetry is this?

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What flower symmetry is this?

What flower symmetry is this?

What flower symmetry is this?

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• If you end up in the weeds, don’t be afraid to ask for help.

• Sometimes you just have to take a mulligan.

Family Flowers Fruit Leaves Special ID Weed Examples

Bean

Fabaceae

5-merous, petals

united

legume (pod) alternate, compound

stipulate

pea-like plant Black medic

Sicklepod

Mallow

Malvaceae

5-merous

anthers fused

capsule or berry alternate, simply stipulate cotton-type plant Venice mallow

Velvetleaf

Milkweed

Ascepiadaceae

Usually white or

greenish; umbel

spindle-shaped

follicle

usually opposite, simple milky juice common milkweed,

honeyvine milkweed

Morningglory

Convolvulaceae

showy, tublar, on

jointed peduncle

2 to 4 seed in

globose capsule

large, alternate

simple

twining herbs Tall morningglory

Field bindweed

Pigweed

Amaranthaceae

no petals, with

prickly bracts

lens-shaped

utricle

alternate, long petioles red succulent

stems

Redroot pigweed

Tumble pigweed

Spurge

Euphorbiaceae

ovary on stalk

inconspicious

3-seeded capsule usually alternate

mostly simple

milky juice

showy bracts

Toothed spurge

Spotted spurge

Sunflower

Asteraceae

composite head achene with

pappus

both alternate & opposite some w/ milky

juice

Common sunflower

Dandelion

Dicot Family Identification