Myriophyllum

Scientific name

Myriophyllum L.

Common names

water milfoil, parrot feather

Family

Haloragaceae

Similar genera

Bacopa, Cabomba, Ceratophyllum, Hippuris, Hottonia, Limnophila, Mayaca, Proserpinaca, Ranunculus

Native distribution

almost cosmopolitancosmopolitan:
(adj) essentially worldwide in distribution
; very diverse in southern hemisphere, especially in Australia

Species cultivated

Myriophyllum aquaticum (Vell.) Verdc.

M. matogrossense Hoehne

M. pinnatum (Walter) Britton, Sterns & Poggenb.

M. simulans Orchard

M. spicatum L.

M. tuberculatum Roxb.

M. ussuriense Maxim.

Adventive distribution

Myriophyllum aquaticum is introduced into numerous counties around the world.

M. heterophyllum Michx. is introduced into Europe and the United States.

M. spicatum is introduced in numerous regions of the world, including North and South America and Southeast Asia.

Weed status

Myriophyllum spicatum is a serious environmental weed in more than 50 countries around the world. M. aquaticum and M. heterophyllum are also recognized as serious environmental weeds.

Habit

submersedsubmersed:
see submerged
and emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
, attached 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

Annual or perennialperennial:
(adj) (of a plant) having a life cycle of more than two years
. Dioeciousdioecious:
(adj) having separate male and female flowers on different individuals of the same species
or monoeciousmonoecious:
(adj) having separate male and female flowers on the same individual
. Adventitiousadventitious:
(adj) of an organ growing where it is not normally expected, e.g., roots growing from a stem
roots often produced from basalbasal:
(adj) at or pertaining to the base, or point of attachment
nodes. Stem elongate, ascending, floating, or erect. Leaves in whorls or sometimes alternatealternate:
(adj) (of leaves) bearing one leaf per node; placed singly on the stem at different heights
or oppositeopposite:
(adj) (of leaves) two leaves per node; in pairs on opposite sides of an axis
, spaced along stem at regularregular:
(adj) uniform in shape or structure; radially symmetrical and parts similar in size and arrangement
intervals, sessilesessile:
(adj) attached directly, without a stalk
; strong heterophyllyheterophyllous:
(adj) with dissimilar leaves on the same plant; often occurs on plants with both submersed and emersed leaves
between submersedsubmersed:
see submerged
and emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
forms; leaf bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
linear, lanceolatelanceolate:
(adj) lance-shaped; widest point below the middle, tapering to the apex
to pinnatepinnate:
(adj) in the form of a feather; of, e.g., leaflets, lobes, or veins: arranged in two rows along an axis
, degree of dissection variable; marginmargin:
(n) edge; rim
entire to serrateserrate:
(adj) (of a leaf margin) bearing sharp teeth pointing forward or to the apex
. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
on emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
stems as a terminalterminal:
(adj) at the apex
spike or axillaryaxillary:
(adj) in, of, or produced from an axil
on apicalapical:
(adj) of the apex
nodes. Flowers sessilesessile:
(adj) attached directly, without a stalk
; sepals 4, reduced, or absent; petals 2-4, white to pink, sometimes absent. Dispersal by seed or stem fragments.

Natural habitat

still or slow flowing water; shallow to deeper waters of lakes, rivers, and streams, especially artificial impoundments

Additional comments

Myriophyllum contains 28 accepted species found mainly in the Southern Hemisphere. Various species are cultivated for aquaria or ponds. The taxonomy of the genus has been problematic, resulting in numerous synonyms being used in the trade. Many species are only suitable for pond culture. All species show distinctive heterophyllyheterophyllous:
(adj) with dissimilar leaves on the same plant; often occurs on plants with both submersed and emersed leaves
between submersedsubmersed:
see submerged
and emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
leaf shape. One species, the chiddarcooping myriophyllum (M. lapidicola Orchard), is found in ephemeral pools on rocky outcrops in western Australia and is considered critically endangered due to habitat destruction and overgrazing. Myriophyllum callitrichoides Orchard, a species from ephemeral rock pools in northern Australia, exhibits atypical growth. This submersedsubmersed:
see submerged
plant has a short, thickened stem basally bearing several short leaves. A short distance above the root mass the stem is divided into numerous, narrow stems mostly without leaves, but each stem terminating in a floating apicalapical:
(adj) of the apex
rosetterosette:
(n) a radiating cluster of leaves, usually close to the ground at the base of a plant
of small ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
leaves.