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Identify An Aquatic Weed

Descriptions of floating and submersed aquatic weeds approved and not approved for control are available below. Both controlled and uncontrolled descriptions in English may be downloaded by clicking on the links.

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Controlled Species

Water Hyacinth
(Eichhornia crassipes)

Floating

Description
  • Free-floating perennial, sometimes rooted in mud
  • Shiny leaves and spongy stalks
  • Lavender to white flowers with a yellow “eye-spot”
  • When non-flowering and intermediate-aged, can be confused with South American spongeplant
  • Native to South America
Growth Period

Spring - late fall; flowers June - October

Habitat
Ponds, sloughs, channels, canals, streams, rivers, lakes

Control Methods Currently
Used By DBW:
Herbicide, Mechanical Removal, Hand Removal


Uruguay Water Primrose
(Ludwigia hexapetala)

Floating

Description
  • Floating to emergent perennial
  • Leaves and stems creep onto land, float on the water surface, or grow upright; upright stems are slightly hairy
  • Oval-shaped (younger) to willow-like (more mature) leaves
  • Bright, showy yellow flowers
  • Native to South America
Growth Period

Spring - late fall; flowers May - December

Habitat
Slow-flowing rivers, lake and reservoir margins, and in the shallow waters of canals and floodplains

Control Methods Currently
Used By DBW:
Herbicide, Mechanical Removal


South American Spongeplant
(Limnobium laevigatum)

Floating

Description
  • Floating to rooted perennial
  • Thick, spongy, floating ovate to spatula-shaped leaves; honeycomb-like spongy tissue on lower surfaces
  • Juveniles develop into mature clumps up to 50 cm (~20 in) tall
  • Small white flowers
  • More mature plants can be confused with water hyacinth
  • Native to Central and South America
Growth Period

Spring - late fall; flowers June - September

Habitat
Ponds, sloughs, channels, canals, streams, lakes

Control Methods Currently
Used By DBW:
Herbicide, Mechanical Removal, Hand Removal


Alligatorweed
(Alternanthera philoxeroides)

Floating

Description
  • Aquatic to terrestrial perennial
  • Aquatic form has hollow stems above and below the water, while terrestrial form has solid stems
  • Lance-like to oval-like leaves that narrow at the base
  • Leaves have distinctive midrib
  • Pleasantly fragrant pearly white flowers
  • Can be confused with water primrose when not in bloom
  • Native to South America
Growth Period

Rapid growth in summer, survives cold winters without long periods of frost; flowers June - October

Habitat
Shallow water in ditches, marshes, pond margins, and slow-moving waterways. May also be found terrestrially in wet soils

 


 

Brazilian Waterweed
(Egeria densa)

Submersed

Description
  • Completely submersed with rooths anchored in the soil
  • 3-6 leaves in a whorled arrangement
  • Middle and upper leaves are between 15-40 mm (~0.50-1.50 in) long and 2-5 mm (~0.10-0.25 in) wide
  • Small white flowers that extend up to 3 cm (~1.25 in) above the water surface
  • Native to South America
Growth Period

Spring - late fall; flowers June - October

Habitat
Slow-flowing or still water in sloughs, canals, river, ponds, lakes, reservoirs; often in nutrient-rich substrates

Control Methods Currently
Used By DBW:
Herbicide


Curlyleaf Pondweed
(Potamogeton crispus)

Submersed

Description
  • Leaves are floating and/or submersed
  • Wavy, stiff, crinkled leaves between 50-76 mm (~2-3 in)
  • Develop turions, or specialized stem buds that survive unfavorable conditions
  • Turions resemble brown pinecones between 7-25 mm (~0.25- 1 in) long
  • Native to Eurasia
Growth Period

Early spring - late summer; flowers May - September

Habitat
Ponds, lakes, streams, rivers, reservoirs, irrigation ditches, marsh area

Control Methods Currently
Used By DBW:
Herbicide


 

Eurasian watermilfoil
(Myriophyllum spicatum)

Submersed

Description
  • Perennial with creeping underground stems; typically submersed, sometimes emergent leaves while flowering
  • Finely divided, whorled leaves with more than 12 leaflet pairs
  • Uniform, parallel, acutely-angled leaf segments
  • Stems and growing tips often red-tinged
  • Does not develop turions, or specialized stem buds that survive unfavorable conditions
  • Small, pinkish, whorled emergent flowers
  • Native to Eurasia and northern Africa
Growth Period

Spring - fall; flowers June - September; plants can die back in winter or remain green

Habitat
Ponds, lakes, rivers, streams, canals, ditches

Control Methods Currently
Used By DBW:
Herbicide


Coontail
(Ceratophyllum demersum)

Submersed

Description
  • Submersed annual to perennial with firm, forked, toothed,
    olive-green to dark green bottlebrush-like leaves
  • Stems up to 2.5 m (~8.2 feet) long
  • Plants lack roots, and are free-floating or anchored by
    specialized buried stems
  • Turions that consist of clusters of scale-like leaves at stem tips
  • Small, inconspicuous, water-pollinated flowers
  • Native to California
Growth Period

Germinates in spring, slow growth through winter; flowers June - October

Habitat
Ponds, slow-flowing streams, ditches

Control Methods Currently
Used By DBW:
Herbicide


 

Fanwort
(Cabomba caroliniana)

Submersed

Description
  • Submersed, rooted to free-floating perennial, but can have floating leaves while flowering
  • Opposite leaves on short stalks without toothed margins
  • Finely divided, red to green fan-shaped leaves
  • Floating leaves are 1-3 cm (~0.40-1.25 in) long
  • Small white to pink to purplish flowers extend above the water surface
  • Introduced from the Eastern United States
Growth Period

Spring - early fall, flowers May - September

Habitat
Ponds, slow-flowing streams, ditches

Control Methods Currently
Used By DBW:
Herbicide


UnControlled Species

Floating Pennywort
(Hydrocotyle ranunculoides)

Description
  • Floating to terrestrial perennial with branched, creeping stems
  • Bare, fleshy, round to kidney-shaped leaves with 3-7 lobes
  • Stalk attaches to the base of the leaf at the margin, unlike other native pennywort species with stalks that attach to the center of the leaf’s underside
  • Shorter flower clusters of 5-10 flowers with greenish- to yellowish-white to purplish petals
  • Native to North America
Growth Period
Rapid growth early spring to early summer, slow growth through winter; flowers March - August

Habitat
Pond and lake margins, marshes, low swamps, slow streams, irrigation and drainage ditches