Plants of
South Australia
Althenia cylindrocarpa
Zannichelliaceae
Long-fruit Water-mat
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Adelaide
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Botanical art

Kath Alcock painting: 1.

Etymology

Althenia named after Jean-Baptiste Joannis Althen (1709 - 1774), an Armenian agronomist who took refuge in France and introduced the cultivation of madder, Rubia tinctorum, in 1760. Cylindrocarpa from the Latin 'cylindri-' meaning cylindrical and the Greek 'karpos' meaning fruit, referring the achene which is dark-brown and cylindrical.

Distribution and status

Found in marine estuaries around the Eyre and York Peninsulas, Kangaroo Island, Gulf St Vincent, Encounter Bay and the Coorong in South Australia, growing in estuaries influenced by tides but not exposed to open seas, fresh to brackish to saline inland waters, in swamps and lake . Also found in Western Australia, Victoria and Tasmania. Native. Common in South Australia. Common in the other states.
Herbarium regions: Eyre Peninsula, Yorke Peninsula, Southern Lofty, Kangaroo Island, South Eastern
NRM regions: Adelaide and Mount Lofty Ranges, Eyre Peninsula, Kangaroo Island, Northern and Yorke, South East
AVH map: SA distribution map (external link)

Plant description

Aquatic, dioecious, annual herb with inflated, membranous leaf sheath and linear leaves to 8 cm long and 0.3 mm wide. Male flowers on slender flexuous, branched shoots to 35 cm tall, borne singly on very short pedicels, initially enclosed within the inflated leaf sheath and then the pedicel elongates at anthesis, to carry the flower well beyond the leaf sheath. Female flowers on slender flexuous branched shoots to 25 cm tall, on pedicels to 10 mm long frequently elongating in the fruit to about 2 cm, to project the mature achenes well beyond the leaf sheath. Fruit a dark brown, cylindrical achene to 3 mm long.

Seed collection and propagation

Collect mature fruits, those that are turning a pale straw colour and contain very small brown seeds. Can collect the whole stem. Place the stem in a tray and leave to dry for a few weeks. Then rub the stems gently by hand to dislodge the seeds. Use a sieve to separate the unwanted material. Be careful as the seeds are very small, less than 2 mm across. Store the seeds with a desiccant such as dried silica beads or dry rice, in an air tight container in a cool and dry place.