oxygen weed, African elodea
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.
Lagarosiphon major declared pest fact sheet PDF from Australia: © Queensland Government: Natural Resources and Mines.
Lagarosiphon major is introduced into Europe (e.g. England, France) and New Zealand.
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.
standing, warm or cold (L. major) waters of lakes and swamps
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.