Lythrum salicaria (Purple Loosestrife)
|Also known as:|
|Habitat:||sun; moist soil; along shores, marshes, wet ditches, wet meadows, floating mats|
|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):|
|National distribution (click map to enlarge):|
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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:
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 occasionally in whorls of 3 or 4. The stem is square and covered in downy hair. Established plants can have dozens of shoots and take on a bushy appearance.
Purple Loosestrife is on the prohibited weed list for Minnesota. It was introduced to the US in the garden trade, quickly escaped cultivation and has been ravaging wetland habitats ever since. It even volunteered in my suburban garden once! It is exceedingly aggressive and can overtake native plants very quickly. The current Minnesota county distribution map doesn't really reflect how widespread this species is in the state; according to EDDMapS, it's currently unreported in only a few western counties, but chances are it is somewhere in those counties, too.
Purple Loosestrife is one of several invasive species with biocontrols: 3 beetles that feed on leaves, flowers or root systems, all of which can impede seed production. The hope of biocontrols may be eradication, but the more realistic goal is to significantly reduce populations and subsequently reduce the impact on native wetland flora and fauna.
Purple Loosestrife is sometimes mistaken for Fireweed (Chamerian angustifolium), which has 4 broad paddle-shaped petals and alternate leaves.
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Where to buy native seed and plants ↓
- Purple Loosestrife plant
- a bushy Purple Loosestrife plant
- more flowers
- a small infestation of Purple Loosestrife
- a larger infestation of Purple Loosestrife
- infestation along a lake shore
- biocontrol Galeracella weevil on Purple Loosestrife
- fruits persist through winter
Photos by K. Chayka and Peter M. Dziuk taken at various locations in Anoka and Ramsey counties.
Have you seen this plant in Minnesota, or have any other comments about it?