Lythrum salicaria
Common name
purple loosestrife
Family
Lythraceae
Flora category
Vascular – Exotic
Structural class
Herbs - Dicotyledons other than Composites
Conservation status
Not applicable
Brief description
Tall emergent perennial herb. Normally 60-100 cm tall, but can grow taller. Purple flowers in dense terminal spikes. Stems are angled (4-6 sided). The stalkless leaves can be opposite, often with alternating pairs at 90 degree angles, or sometimes in whorls of 3 near the base. The upper leaves and floral bracts can be alternate. The leaves are 5-12 cm long, wider and rounded or heart-shaped at the base. Leaf shape varies from lanceolate to narrowly oblong. Leaf sometimes covered with fine hairs.
Distribution
Locally naturalised, especially in Horowhenua and Canterbury.
Habitat
Lake margins and other wetlands.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
FACW: Facultative Wetland
Usually is a hydrophyte but occasionally found in uplands (non-wetlands).
Detailed description
Hairy perennial herb growing from extensive rootstock. Stems 1-2 m tall, square in cross section. Leaves opposite and decussate, lance shaped, without petioles, 20-95 mm long and 5-27 mm wide. Leaf bases tend to be rounded or heart-shaped. Flowers in a branched terminal inflorescence, deep pink, showy; occurring Dec-Feb. Seed capsule blackish, 3-5 mm long. Plants are not self-fertile, so seed is only formed where more than one genotype is present.
Similar taxa
Lythrum virgatum is occasionally cultivated and has a similar growth habit, but smaller in all parts. It is also glabrous and has narrower leaves.
Flowering
December, January, February
Flower colours
Red/Pink
Fruiting
Autumn
Life cycle
Seed or vegetative fragments. Water dispersed, also deliberate planting. Seeds viable for up to 3 years; 2.5 million seeds can be produced per plant.
Year naturalised
1958
Origin
Native to Europe, Asia and Australia.
Reason for introduction
Ornamental pond and garden plant
Control techniques
Notify regional council if found
National Pest Plant Accord species
This plant is listed in the 2020 National Pest Plant Accord. The National Pest Plant Accord (NPPA) is an agreement to prevent the sale and/or distribution of specified pest plants where either formal or casual horticultural trade is the most significant way of spreading the plant in New Zealand. For up to date information and an electronic copy of the 2020 Pest Plant Accord manual (including plant information and images) visit the MPI website.
Tolerances
A wide tolerance of varying physical and chemical conditions (characteristic of disturbed habitats) e.g. tolerates P and N deficiencies by increasing root to shoot ratio; copes with rising water levels by growth in submerged stems; tolerates trampling, cutting, crushing of stems by growing shoot and root buds at the site of damage; adjusts to decrease in light level with changes in leaf morphology. Seeds can germinate in a pH range 4.0-9.1.
Attribution
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA). Tolerance description from Thompson et al., 1987.