Lagarosiphon major
Common name
Lagarosiphon
Family
Hydrocharitaceae
Flora category
Vascular – Exotic
Structural class
Herbs - Monocots
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
Brief 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.
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.
Features
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.
Flowering
January-March
Flower colours
Red/Pink
Fruiting
No seed production known in NZ
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.
Year naturalised
1950
Origin
Africa.
Reason for introduction
Ornamental pond plant
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.
Tolerances
Physical damage and grazing results in resprouting from branches and fragments.
Etymology
major: Greater
Attribution
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA).
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.