Garden yellow loosestrife
Herbaceous perennial wetland invader with yellow flowers. Closely related to the aggressive invasive plant, purple loosestrife.
OverviewOther names for this plant include:
- Common names: garden loosestrife, willowweed, and willowwort
- Scientific names: None.
- It invades wet areas including wetlands, marshes, stream edges, lakes and fens.
- Invasive throughout much of the United States. Banned from sale in Connecticut and Washington state.
- Seeds can remain viable in the soil for up to 20 years.
- Plants reproduce both vegetatively and by seed.
Classification in Wisconsin: Restricted
Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for garden loosestrife was based upon this literature review developed by the department.
Leaves & stems: Lanceolate-shaped leaves are arranged whorled or opposite along erect stems. Undersides of the leaves are softly hairy. Leaves have dot markings.
Flowers: Inflorescence is terminal on the stalks and leafy. The small yellow flowers have 5 petals.
Fruits & seeds: Egg-shaped capsules contain a few seeds.
Roots: Long rhizomes creep along the soil surface.
Similar species: There are a number of native wetland plants in the same family as garden yellow loosestrife that also have yellow flowers (L. quadrifolia, terrestris, ciliata and lanceolata). Many of these do not have dots on the underside of the leaves. Garden yellow loosestrife is similar to its well-known invasive cousin, purple loosestrife (Lythrum salicaria), with different colored flowers and can invade similar habitats.
- Hand-pull individual plants. Be sure to remove the entire rhizome. Monitor for re-growth.
- Cover infestations with black landscape fabric for a minimum of one entire growing season.
- If populations are found near water, be sure to use aquatically-approved herbicides.
- Glyphosate, triclopyr and imazapyr have all been reported as effective.
View pictures of garden yellow loosestrife in our photo gallery!