purple loosestrife

(Lythrum salicaria)

Conservation Status
purple loosestrife
  IUCN Red List

not listed


NNA - Not applicable

SNA - Not applicable


not listed

Weed Status

SN – State noxious weed


Wetland Indicator Status
  Great Plains

OBL - Obligate wetland


OBL - Obligate wetland

  Northcentral & Northeast

OBL - Obligate wetland


Purple loosestrife is an erect, stout, perennial forb that rises on 30 to 50 stems from a taproot and shallow, fibrous roots that develop rhizomes. It can be 12 to 72 tall, though in Minnesota it is usually less than 48 in height.

The stems are erect, square, hairy within the inflorescence, variably hairy above the middle, hairless below. Mature plant stems may be 5- or 6-sided and woody near the base in late summer.

The leaves are opposite below the inflorescence, sometimes alternate within the inflorescence. Sometimes they appear in whorls of 3. They are lance-shaped to nearly linear, 1 to 4 long, and 3 16 to wide, becoming gradually smaller as they ascend the stem. They taper to a point at the tip and are rounded at the base. The larger leaves are somewhat heart-shaped at the base and slightly clasp the stem. The upper and lower surfaces are more or less softly hairy, especially those near the top of the stem. The margins are untoothed.

The inflorescence is a dense, 6 to 14 long, spike-like cluster of numerous flowers at the end of the stem. The flowers are in whorled clusters rising from a pair of hairy, leaf-like bracts. The clusters have 1 or more stalkless flowers and there are 3 to 9 flowers per whorl.

Individual flowers are ½ to 1 wide. There are 5 or 6, sometimes 7, pink to purple petals and the same number of green to purple sepals. The petals are about twice as long as the sepals. The petals are fused at their base with the sepals for most of the sepal length into a hairy, 12-nerved, 3 16 to 5 16 long, 1 16 wide tube (hypanthium). There are always at least 10, usually 12, stamens, in 2 whorls of 5 or 6 each. There are three types of flowers, distinguished as those with short, medium, or long styles. Flowers with short styles have a whorl of long stamens and a whorl of medium length stamens. Flowers with medium-length styles have a whorl of long stamens and a whorl of short stamens. Flowers with long styles have medium to short stamens. The longer stamens protrude well beyond the tube.

The fruit is a two-chambered capsule about long and 1 16 in diameter containing many dust-like seeds.




12 to 72


Flower Color


Pink to purple


Similar Species


Fireweed (Chamerion angustifolium) stem is round. The leaves are alternate. The flower spike is 4 to 5 wide at the base.

Swamp loosestrife (Decodon verticillatus) stems are usually arched and rooting at the tip, not erect. The leaves are usually in whorls of 3 or 4 and are on short leaf stalks. The flowers are in dense clusters in the upper leaf axils.

Winged loosestrife (Lythrum alatum var. alatum), a native plant, is usually hairless. The middle and upper leaves are alternate. The flowers are smaller, ½ across or less, and appear singly in the upper leaf axils. There are always fewer than 10 stamens per flower.


Wet. Fens, marshes, meadows, shores, shallows. Full to partial sun.




July to September




Distribution Map



2, 3, 4, 5, 7, 22, 24, 28.




Native to Europe, Asia, northern Africa, Australia, and the Indian subcontinent. Introduced and naturalized in North America.





  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Superorder Rosanae  


Myrtales (myrtles, evening primroses, and allies)  


Lythraceae (loosestrife)  
  Genus Lythrum (loosestrife)  

Subordinate Taxa






Lythrum salicaria var. gracilior

Lythrum salicaria var. tomentosum

Lythrum salicaria var. vulgare


Common Names


purple loosestrife

purple lythrum

rainbow weed


spiked loosestrife















Describing a leaf that wholly or partly surrounds the stem but does not fuse at the base.



A cup-like tubular structure of a flower formed from the fused bases of sepals, petals, and stamens, that surrounds the pistil. Its presence is diagnostic of many families, including Rose, Gooseberry, and Pea.



A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.



An outer floral leaf, usually green but sometimes colored, at the base of a flower.

Visitor Photos

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Alfredo Colon
  purple loosestrife   purple loosestrife

Not sure if this is Purple Loosestrife or a different type of Loosestrife

  purple loosestrife   purple loosestrife
  purple loosestrife   purple loosestrife
  purple loosestrife   purple loosestrife

This one includes inflorescence.

  purple loosestrife    
MinnesotaSeasons.com Photos


  purple loosestrife    


  purple loosestrife   purple loosestrife


  purple loosestrife   purple loosestrife
  purple loosestrife   purple loosestrife


  purple loosestrife    


  purple loosestrife   purple loosestrife



  Purple loosestrife
Wez Smith
  Purple loosestrife  

Purple loosestrife (Lythrum salicaria).

  Purple Loosestrife (Lythrum salicaria)
Andree Reno Sanborn
  Purple Loosestrife (Lythrum salicaria)  

A very bad and beautiful plant.

  Purple Loosestrife (Lythrum salicaria)
Bill Keim
  Purple Loosestrife (Lythrum salicaria)  
  Lythrum salicaria (Purple Loosestrife)
Allen Chartier
  Lythrum salicaria (Purple Loosestrife)  



Visitor Videos

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Other Videos
  Invaders in Our Waters - Purple Loosestrife

Published on Sep 27, 2012

Purple loosestrife is a wetland plant native to Europe and Asia that was brought to North Americain the early 19th century. This highly invasive plant was likely introduced when its seeds were included in soil used as ballast in European sailing ships and discarded in North America.

For more information visit http://bit.ly/NTNm1z

  Purple Loosestrife: Beauty or Beast?
Entomological Society of America

Uploaded on Feb 1, 2010

This educational video examines the invasive plant, Purple Loosestrife, and the effects it has on the environment. The New Jersey Department of Agriculture is using a beetle (Galerucella pusilla) to control the plant. Directed by Robert Balaam and Robert Chianese; produced by Dr. James Lashomb and Dr. George Hamilton; narrated by Joseph Ingerson-Mahar; filmed and edited by Jianxin Zhang and Hiten Pandya.

  Introduction to Purple Loosestrife
Polk County LWRD

Published on Aug 14, 2012

Learn how to identify and control purple loosestrife

  Purple Loosestrife - A Very Wicked Plant

Published on May 6, 2012

We made this video for the Wicked Plants display at the NC Arboretum. Watch all our wicked plant videos at: http://www.untamedscience.com/wickedplants

  Purple Loosestrife: A Eurasian Invasion
Dexter Wolfe

Uploaded on May 12, 2010

A short educational film about the negative effects of Purple Loosestrife on biodiversity in North America.




Visitor Sightings

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Alfredo Colon

Location: Maplewood Nature Center

purple loosestrife


Location: Upper Gull Lake, Spider Lake, Cass County

purple loosestrife


Location: Lake Shore, Cass County

Not sure if this is Purple Loosestrife or a different type of Loosestrife

purple loosestrife

MinnesotaSeasons.com Sightings




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