Potamogeton

Potamogeton drummondii

Synonyms - Potamogeton tricarinatus misapplied.

Family: - Potamogetonaceae

Names:

Pondweed because it is common in ponds.

Other Names:

Summary:

Floating pondweed is an aquatic native perennial herb of freshwater lakes, swamps and watercourses. The leaves are of two types; the upper floating leaves are elliptic, 20-80 mm long with several parallel veins; the lower leaves are more delicate, usually linear to very narrowly elliptic, 40-120 mm long, translucent, the margin often undulate. The inflorescence is emergent, spike-like with dense clusters of tiny green to brown bisexual flowers. The flowers each have 4 floral segments, 4 stamens and 4 carpels. The fruiting spike is long-stalked, each flower producing 4 tiny beaked fruitlets.

Description:

Cotyledons:

Two.

Leaves:

Stipules - Sheathing membrane, free, often torn, 5-20 mm long.
Petiole - Short petiole or none on submerged leaves. Floating leaves have a 35-80 mm petiole.
Blade - two types; the upper floating leaves are elliptic, 20-80 mm long by 12-45 mm wide with 10-15 parallel veins; the lower leaves are more delicate, usually linear to very narrowly elliptic, 40-120 mm long by 5-20 mm wide, translucent, the margin is often undulate.

Stems:

Up to 2 m long.
Flower stem - usually 30-80 mm long by 1-1.5 mm diameter.

Flower head:

Densely clustered flowers.

Flowers:

Ovary -
Calyx -
Perianth - 1-2 mm long
Stamens -
Anthers -

Fruit:

Dense spike, 10-20 mm long by 5 mm diameter on a stalk (peduncle) usually 30-80 mm long by 1-1.5 mm diameter.

Seeds:

Nutlets 2-2.5 mm long, compressed and distinctly beaked.

Roots:

Rhizome attached to bed.

Key Characters:

Aquatic perennial.
Floating and submerged leaves.
Upper leaves emergent and floating, petiolate, 12-25 mm broad.
Rhizomatous and attached to bed.
Adapted from Flora of Perth

Biology:

Life cycle:

Perennial

Physiology:


Reproduction:

By seeds.

Flowering times:

Summer.
October to February in WA.

Seed Biology and Germination:


Vegetative Propagules:


Hybrids:

Potamogeton ×salicifolius

Allelopathy:

Ecology, Population Dynamics and Dispersal:


Origin and History:

Native to Australia and WA.

Distribution:

NSW, SA, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Freshwater lakes, rivers swamps, dams, reservoirs and running streams.

Climate:

Temperate.

Soil:

Attached to soil in water less than 2 m deep.

Plant Associations:

Algae
Hornwort (Ceratophyllum demersum)
Hydrilla (Hydrilla verticillata)

Significance:

Beneficial:


Detrimental:

Impedes water flows.
May entangle swimmers or children.

Toxicity:

Not recorded as toxic.

Legislation:

None.

Management and Control:

Difficult to remove mechanically as rhizome fragments break off.
Apply 2.5 litres of diquat200 as a uniform injection into each mega litre (1000 m3) of pond water. Spray 2.5 L/ha of diquat onto the floating leaves the following day.
Repeat in 4 weeks time if necessary.

Thresholds:

Eradication strategies:

Apply 2.5 litres of diquat200 as a uniform injection into each mega litre (1000 m3) of pond water. Spray 2.5 L/ha of diquat onto the floating leaves the following day.
Repeat in 4 weeks time if necessary.
On areas that keep coming back apply 300 kg/ha (30 g/m2) of dichlobenil67.5 granules preferably in spring.

Herbicide resistance:

None reported.

Biological Control:


Related plants:

Potamogeton cheesemanii is an Australian native.
Potamogeton crispus (curly pondweed) is introduced.
Potamogeton ochreatus (blunt pondweed) is an Australian native.
Potamogeton reduncus
Potamogeton tepperi
Potamogeton tricarinatus (floating pondweed) a species from the Kimberley and Pilbara regions of northern WA is often confused with Potamogeton drummondii. It has longer fruits.
Potamogeton ×salicifolius

Plants of similar appearance:


References:

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P. Diagram.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (2007). Western Weeds. A guide to the weeds of Western Australia. (Second Edition). Plant Protection Society of Western Australia, Perth, Western Australia. P. Photo.
Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne).
Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P724
Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P123.
Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P. Photo.
Wheeler, Judy, Marchant, Neville and Lewington, Margaret. (2002). Flora of the South West: Bunbury - Augusta - Denmark. (Western Australian Herbarium, Bentley, Western Australia).

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.