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African oxygen weed (Lagarosiphon major)

African oxygen weed Description: This species is listed on the Federal Noxious Weed list and on the Michigan prohibited aquatic plant list.

Habit: Aquatic; perennial; submerged; growing in depths of up to 6 m (20 ft). Forms dense floating mats (up to 3 ft thick).

Leaves: Submersed, greatly recurved, stiff, alternate spirally along the stem, linear to linear-lanceolate, 16 mm (1 in) long by 2 mm (1/16 to 1/8 in) wide, 3-veined with visible midvein, margins minutely toothed at stem tips, leaves are very densely crowded.

Stems: Sparsely branched (every 10-12 nodes); submerged; brittle; 3 mm (1/8 in) diameter; growing up to 20 ft long.

Flowers: Tiny, 3 petals, clear-white in color, female flowers reach surface on long thread-like tubes, male flowers form in the leaf axils, free-floating.

Fruit and seeds: Seed pod, beaked, seeds are 1/ in long, averaging 9 to a capsule.

Habitat: Native to South Africa. Found in freshwater lakes and slow-moving streams, prefers cool waters, high light levels. Tolerates high or low nutrient conditions, high alkalinity and low CO2 levels.

Reproduction: Vegetatively; spread by water currents and boats. Only female plants known outside native range.

Similar species: Hydrilla (Hydrilla verticillata) have teeth on the margins and few teeth on underside midribs.

Monitoring and rapid response: Strong aquatic herbicide, fluridone has been deemed most effective.

Credits: The information provided in this factsheet was gathered from the Michigan Natural Features Inventory and the University of Florida Institute of Food and Agricultural Sciences.

Individual species images that appear with a number in a black box are courtesy of the network ( photo author credits may not be included due to the small display size of the images and subsequent difficulty of reading the provided text. All other images appear courtesy of Google (

Common Name:

African oxygen weed

Scientific Name:

Lagarosiphon major







USDA Symbol:


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