Lagarosiphon

Scientific name

Lagarosiphon Harv.

Common names

oxygen weed, African elodea

Family

Hydrocharitaceae

Native distribution

Africa and Madagascar

Species commonly cultivated

Lagarosiphon cordofanus Casp. (eastern and southern Africa)

L. madagascariensis Casp. (Madagascar)

L. major (Ridl.) Moss (southern Africa, Europe, New Zealand)

U.S. Federal Noxious Weed: Lagarosiphon major

Identification: Lagarosiphon major is distinguishable by its relatively large, recurved leaves; the other two cultivated species have narrow, needle-like leaves.

See Lagarosiphon major disseminule fact sheet.

Lagarosiphon major declared pest fact sheet PDF from Australia: © Queensland Government: Natural Resources and Mines.

Adventive distribution

Lagarosiphon major is introduced into Europe (e.g. England, France) and New Zealand.

Weed status

Lagarosiphon major is a potentially serious weed of cold waters in temperate countries. Lagarosiphon major is a declared federal noxious weed in New Zealand and Australia and is an aquatic weed on the U.S. federal noxious weed list.

Habit

submersed, attached stem plant

Brief description

Perennial. Usually dioecious. Roots unbranched. Stems elongate. Leaves spiral, whorled or subopposite, evenly spaced but denser towards apex, sessile, linear to lanceolate, straight or recurved, with minute denticulate margins. Inflorescence axillary; spathe of 2 united bracts. Flowers unisexual; female spathe cylindrical, subtends single, sessile, minute female flower; male spathe globose, subtends numerous minute male flowers. Male flowers abscise as buds and float on surface; female flower carried to surface on long filiform hypanthium (appears to be a pedicel) and opening; sepals 3; petals 3, similar. Dispersal by seed or stem fragments.

Natural habitat

standing, warm or cold (L. major) waters of lakes and swamps

Additional comments

Rapidly growing species that can quickly dominate other species. All are difficult to cultivate in aquaria. Unbranched roots are used to anchor the plant rather than for nutrient uptake.