New Zealand plants have wrongly been called Isotoma fluviatilis (R.Br.) F.Muell. ex Benth., which is an Australian endemic.
Vascular – Native
Herbs - Dicotyledons other than Composites
2n = 28
Current conservation status
The threat classification status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2017 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants. Authors: By Peter J. de Lange, Jeremy R. Rolfe, John W. Barkla, Shannel P. Courtney, Paul D. Champion, Leon R. Perrie, Sarah M. Beadel, Kerry A. Ford, Ilse Breitwieser, Ines Schönberger, Rowan Hindmarsh-Walls, Peter B. Heenan and Kate Ladley. Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – a suggested threat classification status has not been assessed by the NZTCS panel.
2017 | At Risk – Declining | Qualifiers: DP, RR
Previous conservation statuses
2012 | At Risk – Declining | Qualifiers: RR
2009 | At Risk – Declining
2004 | Not Threatened
Endemic. South Island: Nelson (mainly westerly but also known from Lake Rotoiti) and the West Coast to Fiordland (Milford Sound).
Usually found growing in marginal turf and amongst herbs on the margins of lakes lagoons, stream banks, swamps, and among sand dunes in wet depressions. Also recorded from muddy riverbanks. Sometimes found wholly submerged in water up to 0.5 m deep. Also recorded from damp ground within open stands of kahikatoa (Leptospermum scoparium) and kamahi (Weinmannia racemosa), and in modified habitats such as roadside ditches and pasture.
Wetland plant indicator status rating
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Creeping, prostrate, glabrous herb; rooting at leaf nodes. Leaves alternate, upright to spreading; lamina 7.0–12.0 x 2.0–5.0 mm, lanceolate, narrowly elliptic, to broadly elliptic, notably narrow when submerged or shaded, green, sometimes blotched purple-brown, midvein faint, lateral veins faint to obscure, margin shallowly toothed to sinuate; petiole 1.0–1.5 x 0.4–0.7 mm. Flowers hermaphrodite, resupinate, axillary, solitary; peduncle 1.0–17.0 x 0.4–0.6 mm. Calyx with short tube adnate to ovary; lobes 5, 1.1–1.7 x 0.2–0.5 mm, green, narrow triangular to lanceolate; apex subacute and with conspicuous usually translucent tip. Corolla 5–6 mm long, 3.5–5.0 mm diam. when open, white to lavender; tube 1.5–3.0 x 1.0–1.5 mm diameter, entire, usually glabrous, inner surface rarely with a few hairs; lobes 4–5, lobes 2.2–3.5 x 1.0–1.2 mm, narrow-lanceolate, recurved, glabrous, apex subacute. Filaments 3.0–3.6 x 0.2–0.3 mm, fused below anthers, adnate to corolla tube on lower third, white in distal part, becoming translucent and flushed green toward proximal part. Anthers 0.6–1.1 mm long, united into a tube around style, purple-black, glabrate to sparsely hairy, curved over at top, with small central pore < 0.1 mm diameter; 2 awns and several hairs present at apex on lower anthers, awns up to c. 0.2 mm long, hairs up to c. 0.1 mm long. Nectary annular, c. 0.15 mm high, green; apex usually with hairs, hairs c. 0.2 mm long. Ovary 1.9–2.7 x 1.0–1.2 mm wide, green, apex obtuse. Style 4.0–4.2 mm long, 0.2–0.3 mm wide, white, exserted beyond anthers. Stigma bilobed, lobes 0.3–0.4 x 0.4–0.5 mm, pink, subtended by whorl of hairs, hairs c. 0.2 mm long. Capsule 2.8–5.0 x 2.0–2.5 mm; thin-walled, seeds visible through wall, indehiscent and without apical valves, disintegrating with age; apex crowned with persistent style base; base obtuse to cuneate. Seed broadly elliptic to almost circular, slightly compressed, 0.4–0.6 mm long; apex, testa orange to olive, semi-glossy, glabrous, minutely punctate.
Lobelia fatiscens is distinguished from Lobelia ionantha (formerly Hypsela rivalis) by its leaves which are generally narrowly lanceolate to broadly elliptic; by the corolla petals which are moderately recurved rather than flat; and by the staminal filaments which are adnate only to the lower third of the corolla tube. From Lobelia angulata it differs by the leaves which are mostly entire (rarely with a few faint teeth); corolla which is not split to the base at the back, stamens adnate to the middle of the corolla tube; and by the thin-walled and indehiscent fruit.
August - January
October - May
Easily grown from fresh seed, rooted pieces and by the division of whole plants. However, can be fickle and difficult to maintain. Unlike the true Isotoma fluviatilis, which has attractive blue flowers, the New Zealand plant has relatively small, inconspicuous greenish - white flowers.
lobelia: Named after Lobel, pioneer botanist
fatiscens: From the Latin fatiscens ‘disintegrating, crumbling’
Where To Buy
Not commercially available.
Fact Sheet compiled by P.J. de Lange (12 August 2008). Description from Heenan et al. (2008).
References and further reading
Heenan, P.B.; Knox, E.B.; Courtney, S.P.; Johnson, P.N.; Dawson, M.I. 2008: Generic placement in Lobelia and revised taxonomy for New Zealand species previously in Hypsela and Isotoma (Lobeliaceae). New Zealand Journal of Botany 46: 87-100.
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Lobelia fatiscens Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/lobelia-fatiscens/ (Date website was queried)