What does it look like?
Purple loosestrife is an erect, summer-green perennial herb that grows 1-2 metres tall. The woody stems are square in cross-section, pink at the base and die off in winter. It has narrow leaves, which are usually paired and are heart-shaped at the base. From December to February, it produces 20-25 cm long spikes of purple-magenta flowers. The flowers are followed by blackish seed capsules that are 3-5mm long. It has a long taproot as well as fibrous roots.
Why is it a problem?
Purple loosestrife is a highly aggressive invader of damp ground, wetlands, and riparian habitat. It forms tall, dense, long-lived stands that rapidly out-compete native wetland species. It tolerates hot or cold conditions and low to high nutrient levels, though it is intolerant of salt water.
Purple loosestrife reproduces mostly by seed but regrowth from plant fragments has also been observed. It produces millions of seeds that can remain viable in the soil for many years. Seeds submerged in water can remain viable for 1-2 years. For germination, disturbed sites or open, moist substrates are preferred.
Control methods
Purple loosestrife is a pest plant listed for Eradication in Hawkes Bay’s Regional Pest Management Plan. Please contact us regarding control of this weed on 06 835 9200.
Related links
Notify Council
If you think you've found this pest, please get in touch with our Biosecurity Team at biosecurity@hbrc.govt.nz or call us on 0800 108 838.
Management Programme
Eradication Programme
An Eradication Programme attempts to reduce a pest's level of infestation to zero, across an infestation zone, over a specified time frame. To be successful; the rate of removal must exceed the rate of increase of the pest, reinvasion from other areas must be prevented, and all potentially reproductive individuals must be targeted. For these reasons, eradication programmes require robust design, efficient implementation, sufficient money, and trained field staff to be successful.
More informationNational Pest Plant Accord
All plants on MPI's National Pest Plant Accord (NPPA) are unwanted organisms under the Biosecurity Act 1993 whose formal or casual trade contributes significantly to their spread.
Plants on the Accord cannot legally be propagated, distributed, or sold in New Zealand. If allowed to spread further, these pest plants could seriously damage our economy and environment.
Unwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
More informationRules
Sections 52 and 53 of the Biosecurity Act (1993)
No person shall knowingly communicate, cause to be communicated, release, or cause to be released, or otherwise spread any pest or unwanted organism, in accordance with Sections 52 and 53 of the Biosecurity Act 1993
More informationTaxonomies
FamilyLythraceae
TypePlants
GroupPerennial
HabitatFreshwaterLand
Management ProgrammeEradication ProgrammeNational Pest Plant AccordUnwanted Organism
