Sagittaria
| Botanical Name | Sagittaria graminea ssp platyphylla |
|---|---|
| Family | Alismataceae |
| Origin | North America |
Identification
Sagittaria is an emergent perennial aquatic plant up to 800 mm in height. It has fleshy rhizomes (creeping roots) which are buried and usually submerged below the water surface, while leaves are held above the surface by rigid stems. There are two kinds of leaves. The emergent leaves are linear to ovate, tapering abruptly to a point and are 100 to 250 mm long and 20 to 80 mm wide. The stems holding the emergent leaves are up to 550mm long, triangular in cross section and are winged towards the base. The submerged leaves are strap-shaped, up to 500 mm long and 25 mm broad. The white or sometimes pink flowers are 30 mm in diameter and are found in groups of three-flowered whorls at the end of the flower stem. Flowers are always below leaf height and produce clusters of fruitlets which contain oblong seeds, each 1.5 to 3 mm long. Seeds germinate in spring and flowering occurs from November to March during which period the fruits ripen and shed seed. The fleshy roots (rhizomes) remain dormant during winter, their buds shooting in spring.Habitats
Sagittaria grows in static or slow-moving freshwater such as drains, streams and pond margins, up to a depth of 450 mm.Impact to Biota and Ecosystems
Sagittaria forms extensive infestations in shallow waterways, seriously restricting water flow and increasing sedimentation, thus aggravating flooding.Dispersal Routes, Vectors, Infestation Sources
The plant increases density and spreads locally by its creeping root system. It spreads to other areas through seed carried by water, machinery, wildlife and humans, as well as rhizome fragments being transported by ditch cleaning machinery and spoil.Management
|
Management |
|
| Physical Control |
Plants can be removed manually or mechanically, ensuring all parts of the plant including the root system are removed. Ensure that clearance machinery does not spread seed or plant fragments. |
| Disposal | |
| Chemical Control |
(Another option is to treat all emergent plants with glyphosate (at the rate of 200 ml per 10 litres water with penetrant added) before they flower and seed). |
|
Biological Control |
|
| Recommended Approach | |
Further Comment
The plant can be confused with other species of Sagittaria and with water plantain (Alisma plantago -aquatica), however the latter has "D" shaped stems, with broader, more rounded leaves and a taller flowering stem (0.5 - 2 m high) whilst emergent sagittaria has triangular shaped stems.
Sagittaria is a National Accord Pest Plant. A native of North America, sagittaria has been introduced to many countries as an ornamental aquatic plant. It was first recorded at a field site in New Zealand (on Auckland's North Shore) in 1988.
This plant is prohibited from propagation, sale and distribution within New Zealand!