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Scientific Name
Synonyms
Family
Common Names
Origin
Cultivation
Naturalised Distribution
Habitat
Habit
Distinguishing Features
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Environmental Impact
Legislation
Management
Similar Species
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Click on images to enlarge

large infestation (Photo: Sheldon Navie)

infestation (Photo: Sheldon Navie)

infestation (Photo: Sheldon Navie)

habit with narrower leaves (Photo: Sheldon Navie)

habit with broader leaves (Photo: Sheldon Navie)

the strap-like submerged leaves on young plants (Photo: Sheldon Navie)

elongated emergent leaves (Photo: Sheldon Navie)

broader emergent leaf borne on a thick three-angled stalk (Photo: Sheldon Navie)

female flowers with green centres made up of numerous carpels (Photo: Sheldon Navie)

male flowers with yellow stamens (Photo: Sheldon Navie)

immature fruit (Photo: Sheldon Navie)

young plant (Photo: Sheldon Navie)

Sagittaria platyphylla

Scientific Name

Sagittaria platyphylla (Engelm.) J.G. Sm.

Synonyms

Sagittaria graminea Michx.
Sagittaria graminea Michx. subsp. platyphylla Engelm.
Sagittaria graminea Michx. var. platyphylla Engelm.
Sagittaria graminea Michx. var. weatherbiana (Fernald) Bogin
Sagittaria weatherbiana Fernald

Family

Alismataceae

Common Names

arrow-head, arrowhead, delta arrowhead, grassy arrowhead, sagittaria, slender arrowhead

Origin

Native to eastern USA (i.e. Ohio, Pennsylvania, West Virginia, Illinois, Missouri, Oklahoma, Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, Tennessee and Texas), Mexico and Central America (i.e. Panama).

Cultivation

Sagittaria (Sagittaria platyphylla) is sometimes grown as an ornamental plant in garden ponds and water features.

Naturalised Distribution

This species is widely naturalised, but scattered, in southern and easatern Australia. It is most common in the irrigation areas of northern Victoria and southern New South Wales. Also becoming common in the coastal districts of New South Wales and Queensland, and present in south-eastern South Australia and south-western Western Australia. Was previouslynaturalised in the ACT, but has not been recorded there in the last 30 years.

Habitat

A weed of waterways, marshes, swamps, drainage ditches, irrigation channels and rice crops in warmer temperate, sub-tropical and tropical environments.

Habit

A long-lived (i.e. perennial) aquatic herbaceous plant usually rooted to the ground with stems and leaves emerging up to 80 cm above the water surface. However, plants may sometimes become detached from the substrate form floating mats of vegetation on or near the water surface.

Distinguishing Features

Stems and Leaves

The upright (i.e. erect) flowering stems are produced above the water surface and creeping underground stems (i.e. rhizomes) are also produced in the substrate.

Two distinct types of leaves are also produced by this species. The emergent leaves are large (10-48 cm long and 2-10 cm wide) and borne on long stalks (i.e. petioles) up to 55 cm long. These stalks, which are up to 25 mm thick, are triangular in cross-section and are slightly winged towards the base. The leaf blades are elongated (i.e. lanceolate) or narrowly egg-shaped in outline (i.e. narrowly ovate) with entire margins and pointed tips (i.e. acute apices). They are hairless (i.e. glabrous) and have a shiny appearance. The underwater leaves are strap-like in nature (up to 50 long and 10-25 mm wide) and form a rosette below the water surface.

Flowers and Fruit

Separate male and female (i.e. unisexual) flowers are borne on the same plant (i.e. this species is monoecious). These flowers (about 30 mm across), which are white or sometimes pinkish in colour, are arranged in 2-12 groups (i.e. whorls) of three near the top of the emergent flowering stems. The lower groups of flowers are female (i.e. pistillate) and are borne on stalks (i.e. pedicels) 5-70 mm long that thicken and curve downwards (i.e. become recurved) as the fruit begin to mature. The upper groups of male (i.e. staminate) flowers are slightly larger and do not become recurved. Both types of flowers have three green sepals (3-8 mm long) and three petals (6-16 mm long). Flowering occurs mostly during summer and autumn.

The fruit consists of a mass of numerous one-seeded fruitlets (i.e. achenes) that are densely arranged in a small rounded cluster (5-15 mm across). Individual seeds are oblong in shape (1.5-3 mm long), flattened, with a small projection (i.e. beak) at one end and sometimes with one to three narrow 'wings' on their sides.

Reproduction and Dispersal

This species reproduces by seed, underground tubers (up to 40 mm long and 15 mm wide) and underground stem segments (i.e. rhizomes).

The underground stem fragments and tubers may be dispersed during floods and in dumped aquarium and garden waste. They also facilitate the lateral spread of colonies over time. The seeds are thought to be spread by water movement and animals.

Environmental Impact

Sagittaria (Sagittaria paltyphylla) is regarded as an environmental weed in Queensland, New South Wales and Western Australia, and as an emerging or potential environmental weed in other parts of southern Australia. It was recently listed as a priority environmental weed in at least one Natural Resource Management region.

Legislation

This species is declared under legislation in the following states and territories:

Management

For information on the management of this species see the following resources:

Similar Species

Sagittaria (Sagittaria platyphylla) may be confused with arrowhead (Sagittaria montevidensis), creeping burrhead (Echinodorus cordifolius subsp. cordifolius), water plantain (Alisma plantago-aquatica), alisma (Alisma lanceolatum) and pickerel weed (Pontederia cordata). These species can be distinguished by the following differences: