Plants of
South Australia
Isotoma fluviatilis ssp. australis
Swamp Isotome
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Regional Species Conservation Assessments per IBRA subregion.
Least concern
Near threatened
Critically endangered
Data deficient
Coober Pedy
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Botanical art

Kath Alcock paintings: 3

Prior names

Lobelia inundata

Lobelia fluviatilis

Laurentia fluviatilis

Common names

Swamp Isotome


Isotoma, from the Greek 'isos, meaning equal and 'tomos', meaning a cutting, referring to the equally cut corolla lobes. Fluviatilis, from the Latin 'fluvius', meaning river, alluding to the species' habitat, growing in water. Australis, means of or from the south; referring to the distribution of the species in southern Australia.

Distribution and status

Found in the lower South-east in South Australia, growing in moist places. Also found in New South Wales, Victoria and Tasmania. Native. Rare in South Australia. Common in the other States.
Herbarium region: South Eastern
AVH map: SA distribution map (external link)

Plant description

Mat-forming, glabrous to sparsely and minutely hair perennial herb, rooting at nodes. Leaves oblanceolate to elliptic or obovate, to 15 mm long and 7 mm wide; obtuse to acute; margins sub-entire to toothed. Flowers solitary in axils, irregularly spaced; bisexual, rarely female with white to intense blue or mauvish-blue flowers. Calyx-lobes to 2.5 mm long, corolla to 15 mm long, almost white to intense blue or mauvish-blue, lobes sub-equal or the upper 2 slightly more deeply cleft, tube to 7 mm long; shortly slit; filaments to 8 mm long; anther tube to 2.5 mm long. Flowering between November to January. Fruits are brown conical-cylindrical to ovoid capsule, slightly compressed, to 7 mm long, Seeds are dark-brown elliptical seed to 0.6 mm long and 0.4 mm wide, weakly and irregularly reticulate. Seed embryo type is spathulate, under-developed.

Seed collection and propagation

Collect seeds between December and February. Collect mature capsules; those that are fat, turning a pale straw-colour and containing brown seeds. This can be very time consuming as not all capsules will be mature. Place the capsules in a tray and leave to dry for one weeks. Then rub the capsules gently by hand to dislodge the seeds. Use a sieve to separate the unwanted material. Be careful as the seeds are very small. 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. From two collections, the seed viability was low to high, ranging from 20% to 90%. This may reflect the maturity of the capsules at collection.

Seeds stored:
LocationNo. of seeds
(weight grams)
of plants
Collection number
Collection location
% ViabilityStorage
BGA9,600 (0.59 g)100+13-Dec-2007TST293
South Eastern
19-Sep-200890%+5°C, -18°C
BGA6,400 (0.2 g)50+10-Jan-2008TST353
South Eastern
19-Sep-200820%+5°C, -18°C
Location: BGA — the seeds are stored at the Adelaide Botanic Gardens, MSB — the seeds are stored at the Millennium Seed Bank, Kew, England.
Number of plants: This is the number of plants from which the seeds were collected.
Collection location: The Herbarium of South Australia's region name.
% Viability: Percentage of filled healthy seeds determined by a cut test or x-ray.