Lythrum salicaria (Purple Loosestrife)

Plant Info
Also known as:
Genus:Lythrum
Family:Lythraceae (Loosestrife)
Life cycle:perennial
Origin:Eurasia
Status:
  • Invasive - ERADICATE!
  • Noxious Weed
  • Prohibited or Restricted species
Habitat:sun; moist soil, along shores
Bloom season:July - September
Plant height:2 to 6 feet
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: 6-petals Cluster type: spike

[photo of flowers] Flowers are in a spike up to 20 inches long, densely packed with purple or pinkish-purple flowers. Individual flowers are ½ to ¾ inch across, have 5 to 7 petals (6 is most common), about 10 purple-tipped stamens. The petals have pointed or slightly rounded tips, a dark vein down the middle, and a wrinkled texture like crumpled tissue paper. The tubular calyx holding the flower is yellowish green, ridged, hairy, and has several long prong-like appendages at the tip end. One plant has numerous spikes.

Leaves and stem: Leaf attachment: opposite Leaf attachment: whorl Leaf type: simple

[photo of leaves] Leaves are up to 4 inches long and 1 inch wide, toothless, gradually tapering to a pointed tip, with a rounded or heart-shaped base and no leaf stalk. Attachment is opposite, or may be in whorls of 3 or 4. The main stem is square and covered in downy hair. Established plants can have dozens of shoots and take on a bushy appearance.

Fruit: Fruit type: seed without plume

[photo of fruit] The calyx becomes a receptable for the seed, and turns purplish as it ripens, then drying to brown. A single mature plant can produce well over a million seeds a year.

Notes:

Purple Loosestrife is on the prohibited weed list for Minnesota and was introduced to the US by the nursery industry. It quickly escaped cultivation and has been ravaging wetland habitats ever since. It is exceedingly aggressive and can overtake native plants very quickly. Purple Loosestrife is sometimes mistaken for Fireweed (Chamerian angustifolium), which has 4 broad paddle-shaped petals and alternate leaves.

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More photos

Photos by K. Chayka and Peter M. Dziuk taken at various locations in Ramsey County.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Jeffrey - Minneapolis
on: 2010-05-21 10:32:36

This plant happens to be all over the mississippi downtown as well. Boom Island to St.Anthony falls. I try to pull it out when I can but the roots are quite stubborn.

Posted by: Sandy - Crow Wing and Morrison County
on: 2010-08-07 09:55:51

There are colonies of them growing in the swampy areas in Southern Crow Wing and Northern Morrison Counties. They are beautiful. Too bad they are considered a noxious weed.

Posted by: Deb - Aurora
on: 2011-06-08 07:31:58

This plant is in my flower bed and I cannot rid myself of it. I have literally removed all wanted perrenials and taken out multitudes of feelers of this plant and it continues to return. What can I do????

Posted by: K. Chayka
on: 2011-06-08 16:58:11

I'm not an expert on this particular subject but the DNR does have a web page on this plant at their web site.

You can also contact your county Soil and Water Conservation District and see if they can give you some assistance. Please also see the links from my invasive species page. Good luck with it

Posted by: mark - Morris along the pom de terre
on: 2012-08-21 13:49:28

They weren't in the ditch this spring but now everywhere

Posted by: Ellen S.
on: 2016-10-29 16:10:42

If you live in MN it's possible to get some help from an insect that eats it. Details here: http://www.dnr.state.mn.us/invasives/aquaticplants/purpleloosestrife/biocontrol.html

Posted by: Joe S - SW corner
on: 2017-03-16 00:21:12

I have had one in the garden, in the same spot since 1964. Never spread, never gets invasive in yard. It is usually the prettiest of all my flower and it flowers from June to August. I just can't bring myself to destroy what has turned out to be one of my favorite plants of all time in my yard. It is indestructible, it has been run over, mowed over, survived -35F, survived drought, grasshoppers, deer, name it. It will likely outlive me which will make me happy.

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