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Ducklettuce

(Ottelia alismoides)

Photo of ducklettuce
Photo credit: J. Garg

A common submerged plant in warmer Asian countries is often found in irrigation systems and rice paddies. It spreads by seed and is on the federal noxious weed list in the United States.

Overview map of prohibited classification in WI
Prohibited (red) counties

Other names for this plant include:

  • Scientific names: Stratiotes alismoides

Classification in Wisconsin: Prohibited

Ecological Threat
  • It can invade freshwater lakes, reservoirs, ponds, marshes and ditches making boating, fishing and almost all other water activities difficult.
  • Degrades water quality by blocking the air-water interface and significantly reducing oxygen levels in the water, impacting underwater animals such as fish.
  • Significantly reduces biological diversity: vegetation mats block sunlight, preventing the growth of submerged and emersed plant communities and altering animal communities by blocking access to the water and lowering plants the animals depend on for shelter and nesting.
Identification

Leaves: Oval green leaves submerged, sometimes partly emergent in shallow water.

Flowers: White, three petals with a yellow blotch at the center

Fruits & seeds: tiny oval tan seeds are the primary spread method.

Similar species: May be confused with other aquatic plants such as Echinodorus berteroi.

Distribution

Currently, there have been no reports of ducklettuce in Wisconsin. Have you seen it? Please send us a report.

Control

Mechanical: Tiny populations can be controlled by pulling. Physical removal should be completed before flowering and seed set.

Chemical: Registered aquatic herbicides can temporarily control ducklettuce in small-scale applications. Application of aquatic herbicide requires a permit.

Resources
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