Lagarosiphon

Scientific name

Lagarosiphon Harv.

Common names

oxygen weed, African elodea

Family

Hydrocharitaceae

Similar genera

Elodea, Egeria, Hydrilla, Hydrothrix, Mayaca, Najas, Nechamandra, Tonina

Native distribution

Africa and Madagascar

Species cultivated

Lagarosiphon cordofanus Casp.

L. madagascariensis Casp.

L. major (Ridl.) Moss

U.S. Federal Noxious Weed: Lagarosiphon major

Identification: Lagarosiphon major is distinguishable by its relatively large, recurvedrecurved:
(adj) curved downward or backward
leaves; the other two cultivated species have narrow, needle-like leaves.

See Lagarosiphon major disseminule fact sheet.

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 temperatetemperate:
(adj) of the climatic zone between boreal and tropical
countries, and an aquatic weed on the U.S. federal noxious weed list.

Habit

submersed, attached stem plant

Brief description

Perennial. Usually dioeciousdioecious:
(adj) having separate male and female flowers on different individuals of the same species
. Roots unbranched. Stems elongate. Leaves spiral, whorledwhorled:
(n) bearing whorls; a type of leaf arrangement (phyllotaxis) in which leaves are in whorls
or subopposite, evenly spaced but denser towards apexapex:
(n) the point farthest from the point of attachment; the tip (often pointed)
, sessilesessile:
(adj) attached directly, without a stalk
, linear to lanceolatelanceolate:
(adj) lance-shaped; widest point below the middle, tapering to the apex
, straight or recurvedrecurved:
(adj) curved downward or backward
, with minute denticulatedenticulate:
(adj) minutely dentate; projecting in the form of a small tooth; slightly toothed
margins. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
axillaryaxillary:
(adj) in, of, or produced from an axil
, a spathespathe:
(n) a large bract or bracts subtending and often enclosing an inflorescence
of 2 united bracts. Flowers unisexualunisexual:
(adj) (of a flower) with either stamens (male) or pistils (female) but not both; consisting of only male or female flowers
; female spathespathe:
(n) a large bract or bracts subtending and often enclosing an inflorescence
cylindricalcylindrical:
(adj) forming a nearly true cylinder
, subtends single, sessilesessile:
(adj) attached directly, without a stalk
, minute female flower; male spathespathe:
(n) a large bract or bracts subtending and often enclosing an inflorescence
globoseglobose:
(adj) spherical or nearly so
, subtends numerous minute male flowers. Male flowers absciseabscise:
(n) separating or falling off (as in, e.g., leaves)
as buds and float on surface; female flower carried to surface on long filiformfiliform:
(adj) thread-like; long and thin
hypanthium (appears to be a pedicelpedicel:
(n) the stalk of a single flower in an inflorescence, or of a grass spikelet
) 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.