Purple Loosestrife

Purple Loosestrife at a Glance

The Plant:

A perennial wetland plant, (Lythrum salicaria). Grows 3’—7’ tall with as many as 50 side branches, giving a bushy appearance. Blooms in late summer, with purple to pink flowers.

The Problem:

Invasive! Shades out native species decreasing biodiversity. Large dense patches eliminate food, nesting sites and suitable shelter for wildlife.

How It Spreads:

Primarily by tiny seeds carried on the wind.

Similar Looking Plant:

Fireweed. Fireweed stems are round and flowers have 4 petals. Purple Loosestife stems are boxy or multi-sided and flowers have 5 to 6 petals.

Monitoring Methods:

Visual surveying, on land or by water.

Control Methods Used:

Digging out the roots (difficult for large infestations). Cutting of flower heads (requires extreme care to not inadvertently disperse seeds). Biocontrol with “Cella” beetles—preferred method for moderate or large infestations. See below for more information.

Where Identified:

Patches have been found along the channel between Spider and Island Lakes; along the Manitowish River leading into Island Lake and the Manitowish River below the dam; along Rice Creek; and along the shores of Steeping Stone #1, McCabe, and Wild Rice Lakes.

Need for Volunteer Monitors:

Yes! Purple Loosestrife can be controlled, but regular pervasive growth requires finding and eliminating the plant. Volunteer monitoring is vital.

It is critically important that control efforts are supplemented through monitoring of our waters to ensure that appropriate steps are taken to limit or prevent the spread of Purple Loosestrife. 

Join the effort, contact [email protected] or


Biocontrol with “Cella” beetles

Biocontrol is the favored method in dealing with moderate to larger colonies of Purple Loosestrife.  “Cella beetles”, (Galerucella calmariensis and G. pusilla) are beetles that only eat its host plant, purple loosestrife. Beetles are raised in a controlled area, and when ready are released onto plants in areas with infestations of Purple Lossestrife.

The Discovery Center has partnered with 7th graders from North Lakeland School and the Manitowish Lakes Association for over 10 years and raised and released tens of thousands of cella beetles in our area.  Early in the year, purple loosestrife roots are dug up from a local site and planted in an enclosure. Beetles are captured from known infestations and released on to the plants within the enclosure.  The beetles feed, mate, and reproduce protected from predation.  After a large hatch, beetles are collected and then released on to purple loosestrife plants along our waterways. 

The beetles successfully decrease the vigor, size and seed output of purple loosestrife, allowing native plants to grow and compete. 


To learn more about the cella beetles and local control of Purple Loosestrife, watch this video prepared by North Lakeland Discovery Center staff.