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Lythrum salicaria L.

Family: Lythraceae
Common names: Purple loosestrife, spiked loosestrife
Category: proposed 1a NEMBA

Lythrum salicaria Description
Perennial herb, 2 m tall. Stems erect, numerous, four-angled, from root stalk up to 2.5 m high. Leaves opposite or in whorls of three, grass green in colour, 3-10 cm long and 1-2 cm wide. Flowers rose-purple, 10-15 mm in diameter, forming a dense spike 150-250 mm long. Fruits small capsules, 3-5 mm long. Seeds small, numerous. Flowering time: throughout summer.

Distribution
Native to Europe, Asia, Northern Africa and Australia. Invasive in Canada, U.S.A, South and West Africa.

History in South Africa
Purple loosestrife was introduced into South Africa either accidentally or for ornamental purposes. It has been recorded only in the Liesbeeck River in Cape Town.

Lythrum salicaria

Environmental and economic impacts
Purple loosestrife invades natural and disturbed wetlands, such as stream banks, lakeshores, marshes, fens, canals, reservoirs, and sub-irrigated pastures. Once the plant is established it can tolerate drier sites, posing a threat to agricultural lands and pastures and also quickly crowding out native vegetation. At high densities, purple loosestrife can create near-monocultures.

How it spreads
Purple loosestrife spreads by seed. It may also spread vegetatively from root or stem segments.

How to eradicate

Once established it becomes difficult to eradicate Lythrum salicaria. Mechanical control can be used at an early stage of growth. No herbicides are registered for this plant in South Africa, but Seismic, an aquatic friendly systematic glyphosate (approved by the register on a trial basis) has been effective so far.

What can you do to help?
Report sightings of these plants to the Early Detection and Rapid Response Programme (EDRR) at SANBI. We will need to know its locality (the exact locality, supply any landmarks or GPS information if possible).
 
Contact person
Khanyisa Jama
Email address: alienplants@sanbi.org.za
Tel: 0217998762

References

  • Henderson, L. 2001. Alien weeds and invasive plants. Plant. Protection Research Institute Handbook No. 12. Agricultural Research Council, Pretoria
  • Invasive species in South Africa. 2010. Lythrum salicaria. Working for water nursery partnership programme. South Africa. Available on http://invasives.org.za/flora-listed-invasives/hydrocleys-nymphoides.html.
  • South African plants invaders atlas database. ARC - Plant protection research institute, Pretoria, South Africa. Available on: www.agis.agric.za
  • South African Plant Invaders Atlas. 2010. SAPIA News no. 17. ARC-Plant Protection Research Institute. Available on http://www.dargieconservancy.org.za/documents/sapia07.pdf
  • Farnesworth, E.J., and D.R. Ellis. 2001. Is purple loosestrife (Lythrum salicaria) an invasive threat to freshwater wetlands? Conflicting evidence from several ecological metrics. Wetlands. 21: 199-209.

See more on invasive alien plants and their categories

Prepared by Buhle Mthembu
November 2011

Last updated on 14 November 2011