Ludwigia peploides subsp. montevidensis
NPPA pest plant
Environmental Weed (2024)
Common names
water primrose, primrose willow
Biostatus
Exotic
Category
Vascular
Structural class
Herbs - Dicotyledons other than Composites
Simplified description
Sprawling emergent perennial herb, characterised by rapid growth that can smother other vegetation. Primrose willow has branched stems with roots at the nodes, either attached to soil or hanging in the water. The leaves are alternate and obtuse, and up to 6 cm long. Their upper surfaces are glossy and they taper into petioles that are up to 2.8 cm long, with two dark green, swollen, rounded stipules at the base. The flowers are up to 2 cm, bright yellow, and arise on stalks from the leaf axils.
Flower colours
Yellow
Detailed description
Herb, forming large patches; stems creeping or floating, rooting at nodes, with pneumatophores sometimes present below water; flowering stems ascending, with patent hairs or more regularly glabrate. Lvs alternate; petiole 0.5-3 cm long, glabrous or somewhat hairy. Lamina 2-8 X o.7-3 cm, elliptic, oblanceolate or obovate, glabrous except for midrib near base; base cuneate to attenuate; apex obtuse to rounded. Fls solitary, 4-5-merous; pedicels 1.5-4.5 cm long at anthesis, generally with patent hairs. Sepals 6-8 mm long, narrow-triangular or lanceolate-oblong, scarcely accrescent; apex emarginate. Petals 1.5-1.7 mm long, bright yellow. Stamens 8 or 10; filaments unequal. Style c. 4 mm long, stout, hairy. Stamina slightly 4-lobed. Capsule 2-2.7 cm long, narrow-cylindrical, ribbed, woody, glabrouse or glabrate. Seeds firmly embedded in cubes of woody endocarp c. 1.5 mm thick, uniserate in each locule.
Similar taxa
Other Ludwigia species and alligator weed (Alternanthera philoxeroides). All these plants have opposite rather than alternate leaves.
Distribution
Locally naturalised in the North Island (Northland, Auckland, Waikato and Manawatu).
Habitat
Still and slow flowing shallow water bodies.
Conservation status
Not applicable
Detailed taxonomy
Family
Onagraceae
Ecology
Flowering
November to February
Year naturalised
1933
Origin
Native of South America and eastern states of Australia
Reason for introduction
Ornamental pond plant.
Control techniques
Generally not controlled in New Zealand, but problematic in Europe/North America. Can be controlled manually, mechanically or herbicidally depending on situation.
Life cycle and dispersal
Stem fragments and seed.
Propagation technique
Native of South America and eastern states of Australia
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]
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Other information
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.
Environmental Weed (2024)
This plant is named in a list of 386 environmental weeds in New Zealand 2024 prepared by DOC. 759 candidate species were considered for inclusion on this new comprehensive list of environmental weeds in New Zealand. The species considered were drawn from published lists of weed species, lists of plants that must be reported or managed by law if observed, existing national and regional programmes and agreements for pest management, and species already managed by the Department of Conservation (DOC). Candidate species were then assessed to see if they were fully naturalised and whether they have more than minor impacts in natural ecosystems. Read the full report here.
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
LUDPSM
Referencing and citations
References and further reading
Champion et al (2012). Freshwater Pests of New Zealand. NIWA publication. http://www.niwa.co.nz/freshwater-and-estuaries/management-tools/identification-guides-and-fact-sheets/freshwater-pest-species.
Johnson PN, Brooke PA (1989). Wetland plants in New Zealand. DSIR Field Guide, DSIR Publishing, Wellington. 319pp.
Aston, H (1977). Aquatic plants of Australia. Melbourne University Press, 367PP.; Popay et al (2010). An illustrated guide to common weeds of New Zealand, third edition. NZ Plant Protection Society Inc, 416pp.
Coffey BT, Clayton JS (1988). New Zealand water plants: a guide to plants found in New Zealand freshwaters. Ruakura Agricultural Cente. 65pp.
DiTomaso JM, EA Healy (2003). Aquatic and riparian weeds of the west. University of California Agriculture and Natural Resources Publication 3421, 462pp.
WSDE (2001). An aquatic plant identification manual for Washington’s freshwater plants. Washington State Department of Ecology, 195pp.
Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. (1988). Flora of New Zealand Volume 4: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.
Attribution
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA). Features description from Webb et. al., 1988.