Lagarosiphon major
NPPA pest plant
Environmental Weed (2024)
Common names
Lagarosiphon
Biostatus
Exotic
Category
Vascular
Structural class
Herbs - Monocots
Simplified description
Submerged perennial bottom rooted oxygenweed. It is characterised by strongly recurved leaves along the stem that are arranged spirally and closely-packed, even more so towards the shoot apex. Leaves are dark green and up to 16 mm long and 2mm wide and gradually tapering to an acute tip. The stems are long, slender, brittle and much branched. The flowers are minute, only 0.25 mm in diameter on fine filamentous stems up to 6 cm long found in the upper leaf bases.
Flower colours
Red/Pink
Detailed description
Vigorous submerged bottom rooting aquatic perennial reaching depths of 6.5m. Stems slender, brittle and much branched. Leaves are dark green, alternate and crowded and overlapping toward the apex of the stem. They are also stiff and curved downwards, are gradually tapered towards the tip, usually 6 to 20 mm long, and have minute marginal serrations. Flowers are tiny 0.25 mm in diameter and up to 6 mm long, pinkish and occur threadlike from the axils of upper leaves. Only female plants have been collected in New Zealand.
Similar taxa
Canadian pondweed (Elodea canadensis) and egeria (Egeria densa). Both of these species have leaves arranged in whorls on the stem, whereas lagarosiphon has leaves arranged alternately in a spiral pattern and leaves are downward curving.
Distribution
Widely naturalised in North Island and lowland northern and eastern South island, rare in Westland and upland South Island.
Habitat
Moderately fast flowing to still water bodies. Waters of low fertility, clear streams and lakes.
Conservation status
Not applicable
Detailed taxonomy
Family
Hydrocharitaceae
Ecology
Flowering
January-March
Fruiting
No seed production known in NZ
Year naturalised
1950
Origin
Africa.
Reason for introduction
Ornamental pond plant
Tolerances
Physical damage and grazing results in resprouting from branches and fragments.
Control techniques
Plants can be physically removed from the lake or waterway using SCUBA or snorkel divers for small scale infestations, or using mechanical diggers. But the appropriateness of these methods is site specific, and the potential for contamination of other sites by mechanical equipment is a signficant concern. There are a number of manipulations to the habitat that in theory can control lagarosiphon (e.g., shading, bottom lining, water drawdown) but there are significant limits to their practical application, rendering them site (or waterbody) specific. The only chemical products registered for aquatic use in New Zealand that are efficacious on lagarosiphon are diquat and endothall. Diquat is a relatively fast acting contact herbicide, which interrupts the electron transport system in plant photosynthesis and causes the destruction of cell membranes and desiccation. At present the introduced grass carp (Ctenopharyngodon idella) are the only biocontrol agent available to manage lagarosiphon.
Life cycle
Perennial. New plants develop from stem fragments which can produce adventitious roots. There is no seed production in New Zealand, with only female plants of this species being present here.
Stem fragments are easily dispersed within catchments by water flow. New catchments are colonised by contaminated boats and trailers (occasionally motor cooling water), eel nets, diggers, people liberating fish, and emptying aquaria. Birds are unlikely to be a factor.
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
Etymology
major: Greater
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.
LAGMAJ
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.
Coffey BT, Clayton JS (1988). New Zealand water plants: a guide to plants found in New Zealand freshwaters. Ruakura Agricultural Cente. 65pp.
Popay et al (2010). An illustrated guide to common weeds of New Zealand, third edition. NZ Plant Protection Society Inc, 416pp. ;Hofstra D, P Champion, (2006). Management options assessment for Lagarosiphon major. NIWA Client Report HAM2006-161.
Hofstra D, P Champion, (2006). Organism Consequence Assessment Lagarosiphon major. NIWA Client Report: HAM2006-058h.
Sculthorpe C D (1967). The biology of aquatic vascular plants. Edward Arnold Publishing, 610pp.
Attribution
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA).