Unwanted Organism, National Pest Plant Accord
- Scientific Name: Myriophyllum aquaticum
- Origin: Native to South America
- Type: Weed
- Plant Life-form Type: Marginal sprawling
- Taxonomy: (Vell. Conc.) Verdc.
- Presence: Widely naturalised, first record from Palmerston North, Manawatu in 1929
- Habitat: Still and slow flowing water bodies
- Temperature (°C): 16 - 23
- pH range: 6.8 - 8.0
- Hardness (ppm): 50 - 200
- Light: Strong
- Difficulty: Demanding
- Notes: Currently a major sprawling emergent weed, affecting a wide range of habitats. A weed in many warm temperate countries.
- Propagation: Propagation and spread is by stem fragmentation and lateral stem growth. It does not produce viable seed in New Zealand, with only female flowers known to exist here
- Features: Sprawling emergent perennial herb. Emergent leaves are a light bluish-green, up to 3.5 cm long, and deeply divided (pinnate), giving them a feathery appearance. They are arranged in whorls of 4-6. The stem can be up to 2m long, but with only up to the top 10 cm emerging above water. Flowers are white, tiny (up to 1.5mm across), with no petals, and attached at the leaf-stem axil.
- Source: TIFBIS
- Regional: Regional Pest Management Strategy: MBH, WTC, AUK, HKB, NSN/TAS.