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oxygen weed

Oxygen weed

Separate male and female flowers are produced on separate plants (i.e. they are dioecious), and only female plants are found in Australia. Both types of flowers are small (less than 3 mm across) and borne in the upper leaf forks (i.e. axils). The female flowers are borne singly on a long thread-like stalk (i.e. filamentous hypanthium). They are pink or purplish in colour and have six minute ‘petals’ (i.e. perianth lobes or tepals). Flowering occurs mostly during summer and early autumn.

Lagarosiphon (Lagarosiphon major) grows extremely quickly from the bottom waterbodies and forms dense mats of vegetation several metres thick at or just below the water surface. It will withstand low light levels, and can grow in water more than 6 m deep. Its canopy spreads out across the upper levels of a waterbody, thereby shading out and out-competing other underwater species. Lagarosiphon (Lagarosiphon major) can dominate freshwater lakes, dams and slow-moving streams and has the potential to become a troublesome weed of such habitats throughout the temperate and sub-tropical regions of Australia.
Dense infestations are generally produced in nutrient-enriched waters. Such infestations can block light penetration, out-competing and displacing native water plants and affecting associated populations of aquatic invertebrates. They can also deplete oxygen levels in the water, thereby making waterbodies less habitable by native fish and waterbirds.

Lagarosiphon (Lagarosiphon major) is a significant problem weed in New Zealand, where it completely dominates waterbodies, preventing their use for recreational activities such as swimming, boating and fishing. It has an early competitive advantage which allows it to successfully out-compete native species such as milfoils (Myriophyllum spp.) and pondweeds (Potamogeton spp.).
The elongated and strap-like leaves are alternately arranged along the stems in a distinctive spiralling pattern. These leaves (5-20 mm long and 2-3 mm wide) are stalkless (i.e. sessile) and are densely clustered towards the tips of the branches. They are strongly curved downwards (i.e. reflexed) and have minute teeth along their margins.
The creeping underground stems (i.e. rhizomes) allow colonies of this weed to increase in size and spread laterally across or along a water body. Stem fragments are usually introduced into new water bodies in dumped aquarium waste are spread down catchments by water movement and floods.
A potential weed of slow-moving waterways, ponds, lakes and dams, that is mainly a threat to the temperate regions of Australia.
Dense infestations are generally produced in nutrient-enriched waters. Such infestations can block light penetration, out-competing and displacing native water plants and affecting associated populations of aquatic invertebrates. They can also deplete oxygen levels in the water, thereby making waterbodies less habitable by native fish and waterbirds.

A submerged, long-lived (i.e. perennial), freshwater plant with stems that are usually rooted to the substrate. It also produces creeping underground stems (i.e. rhizomes).

African oxygen weed Lagarosiphon (Lagarosiphon major) is on the “Alert List for Environmental Weeds”, a list of 28 non-native plants that have the potential to seriously degrade