Sagittaria is from the Latin sagita meaning arrow and refers to the arrow shaped leaves on some species in this genus.
Graminea is Latin for grass-like and refers to long thin grass like submerged leaves on this species.
Sagittaria
Other names:
Arrowhead
Delta Arrowhead (USA)
Slender Arrowhead (USA).
Summary:
An emergent, aquatic perennial arising from tubers produced at the end of rhizomes or stolons from the parent plant that has roots in the mud.
Description:
Cotyledons:
One.
Leaves:
Two types, submerged leaves and emergent leaves held out of the water.
Clustered on the tuber.
Petiole - Up to 500 mm long, triangular in cross section with wings on the inside edges near the base.
Blade - Submerged leaves are strap-shaped without a wider blade, up to 500 mm long by 25 mm wide.
Emergent leaves, 100-250 mm long by 20-80 mm wide, linear or egg shaped, tapering to a pointed tip.
Stems:
Short submerged rhizomes with tubers.
Flower head:
Lower than the leaves. 2-12 rings(whorls) of 3 flowers on the upper part of the stalk which is usually 50-200 mm long and occasionally up to 1200 mm long and erect or bent near the middle. Lower whorls have female flowers, upper whorls male flowered. Female flowers on 5-65 mm long upward bending flower stalks that become thick and curved when in fruit. Male flowers on slightly longer and thinner stalks.
Flowers:
White or pink, 30 mm diameter. Male and female flowers.
Ovary -
Sepals - 3, bent back at maturity.
Petals - 3
Stamens -
Anthers -
Fruit:
5-15 mm diameter clusters of 1 seeded fruitlets.
Seeds:
Oblong, flattened, 1.5-3 mm long, wing on the back, beaked tip.
Roots:
Short fleshy rootstock with many brown fibrous roots in the mud.
Fleshy rhizomes and tubers.
Key Characters:
Biology:
Life cycle:
New infestations arise from seed or tubers. Seeds germinate in spring as water temperatures rise. About a month later the young plant begins to produce horizontal rhizomes and/or stolons and tubers form at the tips. Flowering stem emerge in summer and flowering continues until late autumn. From the tubers new plants arise which in turn produce further rhizomes and tubers. In Australia flowers and early fruits have been found in January and February and flowers and ripe fruit in June. Tubers and rhizomes are dormant in winter and shoot in spring.
Physiology:
Light quantity and quality probably control tuber and rhizome formation.
Optimum growth is at water temperatures around 24oC.
May release methane.
Reproduction:
By seeds, rhizomes and tubers.
Flowering times:
January to June.
Seed Biology and Germination:
Vegetative Propagules:
Rhizomes and tubers.
Hybrids:
Subspecies Sagittaria graminea ssp. platyphylla is the common subspecies in Australia.
Allelopathy:
Population Dynamics and Dispersal:
Spread by seeds, rhizomes and tubers. The main spread is by tubers and rhizomes increasing the size of colonies. Occasionally mats of Sagittaria break off and float downstream. Seed may also float some distance and duck may pass it or transport it in attached mud.
Origin and History:
North America.
First recorded as naturalised in QLD in 1959, Vic in 1962, NSW in 1964 and SA in 1981.
Distribution:
ACT, NSW, QLD, SA, VIC.
Most current infestations are in NSW.
Habitats:
Fresh water, in drainage and irrigation channels and rice fields and shallowly flooded areas.
In water to 450 mm deep.
Climate:
Warm temperate. Sub tropical.
Soil:
Mud under shallow water.
Plant Associations:
Significance:
Secondary and prohibited weeds.
Beneficial:
Ornamental.
Detrimental:
Weed of drains, irrigation channels, streams, swamps and rice fields.
These species obstruct water flow and accelerates silt deposition.
Toxicity:
Not recorded as toxic.
Legislation:
Noxious weed of SA, TAS and WA.
Management and Control:
Ploughing channel beds to expose tubers and rhizomes to frost and drying provides some control.
Increase water depth if possible.
Metsulfuron, 2,4-D and glyphosate give good control.
Thresholds:
Eradication strategies:
Herbicide resistance:
Biological Control:
Some agents have been tested in other countries without success. Carp and spoonbills may have controlled it in the Murray River in SA.
Related plants:
Arrowhead (Sagittaria montevidensis) the blade is broadly or narrowly arrow shaped with obvious veins and the flower stalk is up to 750 mm long and occasionally branched at the last whorl.
Sagittaria sagittifolia.
Plants of similar appearance:
Arum Lily (Zantedeschia aethiopica) has very large white flowers.
References:
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P14.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P730.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P234-235.
Hyde-Wyatt, B.H. and Morris, D.I. (1980) The Noxious and Secondary Weeds of Tasmania. (Tasmanian Department of Agriculture, Hobart, Tasmania). P127.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #1079.1, 1079.2.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P34-36. Photos.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.