Najas

Scientific name

Najas L.

Common names

naiad, water nymph

Family

Hydrocharitaceae

Similar genera

Blyxa, Chara, Heteranthera, Lagarosiphon, Nechamandra, Potamogeton

Native distribution

cosmopolitancosmopolitan:
(adj) essentially worldwide in distribution

Species cultivated

Najas conferta (A. Braun) A. Braun

N. graminea Delile

N. guadalupensis (Spreng.) Magnus

N. indica (Willd.) Cham.

N. marina L.

Adventive distribution

Najas gracillima (A.Braun ex Engelm.) Magnus is introduced into Europe.

N. graminea, N. marina, and N. minor All. have been introduced into numerous countries.

Weed status

Najas graminea and N. marina are troublesome weeds in irrigation canals in numerous countries.

Habit

submersedsubmersed:
see submerged
, much-branched stem plantstem plant:
(n) (a term used in the aquarium and pond plant trade) having an elongate stem (as opposed to a compact stem)

Brief description

Perennialperennial:
(adj) (of a plant) having a life cycle of more than two years
or annual, obligate submergedsubmerged:
(adj) (syn. submersed) under water; submerged below the water surface
, attached. Monoeciousmonoecious:
(adj) having separate male and female flowers on the same individual
or dioeciousdioecious:
(adj) having separate male and female flowers on different individuals of the same species
. Stems slender, much-branched. Leaves alternatealternate:
(adj) (of leaves) bearing one leaf per node; placed singly on the stem at different heights
, appearing whorledwhorled:
(n) bearing whorls; a type of leaf arrangement (phyllotaxis) in which leaves are in whorls
or clustered, linear; base with distinctive dilated sheath; marginmargin:
(n) edge; rim
serrateserrate:
(adj) (of a leaf margin) bearing sharp teeth pointing forward or to the apex
to toothed. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
inconspicuous. Flowers axillaryaxillary:
(adj) in, of, or produced from an axil
, solitary or clustered, sessilesessile:
(adj) attached directly, without a stalk
, unisexualunisexual:
(adj) (of a flower) with either stamens (male) or pistils (female) but not both; consisting of only male or female flowers
. Dispersal by stem fragments or seed.

Natural habitat

all types of water bodies

Additional comments

Najas are slender plants, often brittle and frequently forming large monoclonal stands. The genus contains 38 accepted species plus some subspecies worldwide and is occasionally cultivated for aquaria. Previously placed in its own family, Najadaceae, but more recently placed in Hydrocharitaceae based on phylogenetic evidence.