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Wisconsin Plant of the Week

Lythrum alatum Pursh

Lythraceae (Loosestrife Family)

Common Name:

winged loosestrife

07/15/2001

Winged loosestrife is a native perennial that grows to 1 m in sunny wet meadows, prairies, marshes and wherever soil is moist or wet most of the time.

Plants in the loosestrife family have 6 petals and sepals joined to form a hollow tube.  The petals are usually crumpled in bud like crepe paper. The number of stamens vary in the family but they’re always attached to the petals at two different levels. The styles are in 2 or 3 series, each a different height.  The stamen and style arrangements combine to minimize pollen transfer within the same flower and promote outcrossing.  Most species form a long capsule with many very tiny seeds. These have little reserves so germination requires open continually moist soil conditions.

Winged loosestrife flowers bloom from June to September, either singly or occasionally paired in the axils of upper leaves and on very short stalks. They have 6 stamens.

Leaf arrangement is unusual -- the upper leaves are alternate, and the lower usually opposite.  Leaves are simple, entire, and smooth,  pointed at the tip and rounded at the base, less than 5 cm long and  attached directly to the stem. 

The stem is 4-angled, very slightly winged between the leaves, stiffly branching and erect. The species name actually refers to the 12 wings at the base of each flower, where the petals and sepals fuse, but neither “winged” feature is very prominent.

Other similar common members of the loosestrife family are the non-native purple loosestrife (L. salicaria) and water-willow (Decodon verticillatus).).   Purple loosestrife has many flowers in crowded spikes, 12 stamens, and no alternate leaves. Water willow has flowers similar to those of winged loosestrife, but water-willow has long arching stems and white spongy roots that allow it to float on the water.

The leaf-feeding beetles (Galerucella) introduced as a biocontrol on invasive purple loosestrife, prefer that species to winged loosestrife and will only feed on winged loosestrife where purple loosestrife is not available.

  • Origin of the name: Lythrum, Gr., luthron, dried blood, refers to the color of the flower in some species or to its ancient medicinal use to stop bleeding; alatum, L. alatus, winged
  • Range: Eastern N. America, west to the Rocky Mts.
  • WI Range: North to Oconto County, but most common in southern and southeastern prairies
  • Common associates: Bluejoint grass, tussock sedge, marsh milkweed, mountain mint
  • Wetland Indicator Status: OBL
  • Coefficient of Conservatism: C = 7 (S&W), C = 9 (MI)
     
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