Lythrum

Scientific name

Lythrum L.

Common names

loosestrife

Family

Lythraceae

Similar genera

Ammannia, Hypericum, Ludwigia, Lysimachia, Mimulus, Nesaea, Rotala

Native distribution

North America, Europe, Africa, Asia, Australia

Species cultivated

Lythrum alatum Pursh.

L. salicaria L.

L. virgatum L.

Adventive distribution

Lythrum hyssopifolia L. is introduced into North America, New Zealand and Australia, where it may be native.

L. junceum Banks & Sol. is introduced into Australia and New Zealand

L. salicaria L. is introduced into Australia, New Zealand and North America

L. portula (L.) D.A. Webb, L. thymifolia L., L. tribracteatum Salzm. ex Spreng. and L. virgatum L. are introduced into North America.

Weed status

Lythrum salicaria (purple loosestrife) is declared a noxious weed in many countries; L. virgatum is also considered a noxious weed.

Habit

small herb to medium-sized shrub, emergent

Brief description

Stem erect, creeping or floating. Leaves oppositeopposite:
(adj) (of leaves) two leaves per node; in pairs on opposite sides of an axis
, whorledwhorled:
(n) bearing whorls; a type of leaf arrangement (phyllotaxis) in which leaves are in whorls
or alternatealternate:
(adj) (of leaves) bearing one leaf per node; placed singly on the stem at different heights
, usually sessilesessile:
(adj) attached directly, without a stalk
; leaf bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
linear to ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
or obovateobovate:
(adj) ovate, with the narrow end at the base
; base acuteacute:
(adj) tapering to a sharp, pointed apex with more or less straight sides; broader than acuminate; forming an angle of less than 90 degrees
, obtuseobtuse:
(adj) with a blunt or rounded apex and sides coming together at an angle of more than 90 degrees
to cordatecordate:
(adj) heart-shaped; in the form of two rounded lobes
. Flowers actinomorphicactinomorphic:
(adj) of flowers, having radial symmetry; capable of being bisected into identifical halves along more than one axis
or slightly zygomorphiczygomorphic:
(adj) bilaterally symmetrical; symmetrical along only one plane
, solitary in leaf axils or in complex inflorescences, usually a terminalterminal:
(adj) at the apex
spikespike:
(n) an indeterminate, unbranching inflorescence of sessile flowers or flower clusters on a usually elongated axis
. Sepalsepal:
(n) a member of the outer envelope of a flower (calyx)
tube campanulatecampanulate:
(adj) bell-shaped
to tubulartubular:
(adj) (of a corolla, perianth, calyx tube or other structure) (1) tube-shaped; cylindrical: narrow and elongate with more or less straight sides; (2) having segments fused into a tube (of any shape)
, lobes 6 (4); petals usually 6 (4), pink to purple. Propagules are seeds.

Natural habitat

littoral, wet ground, and marginal shallows

Additional comments

Lythrum contains 30 species, typically wetland species with about six aquatic. Lythrum virgatum is similar to L. salicaria but has narrower, glabrousglabrous:
(adj) without hairs or scales
leaves with acuteacute:
(adj) tapering to a sharp, pointed apex with more or less straight sides; broader than acuminate; forming an angle of less than 90 degrees
base and flowers in a leafy racemeraceme:
(n) an indeterminate, unbranched inflorescence having pedicelled flowers on a usually elongated axis (may be cymose)
.