Utricularia australis
Common name
Yellow bladderwort
Synonyms
Utricularia protrusa Hook.f., U. mairii Cheeseman
Family
Lentibulariaceae
Flora category
Vascular – Native
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Structural class
Dicotyledonous Herbs other than Composites
Current conservation status
The conservation 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). 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.
2012 | Threatened – Nationally Critical | Qualifiers: RF, RR, SO
Previous conservation statuses
2009 | Threatened – Nationally Endangered | Qualifiers: RR, SO
2004 | Gradual Decline
Distribution
Indigenous. In New Zealand known only from the North Island, from Te Paki to Lake Taupo, and near Paekakariki. Also present in Australia and Europe.
Habitat
Coastal to lowland. Peat lakes, peaty pools and slow-moving streams draining peat bogs. Often found floating near or amongst spikerush (Eleocharis sphacelata R.Br.). U. australis appears to prefer shallow, still water, in sunny situations with little or no competition from other submerged aquatic plants.
Features
Wholly submerged, floating carnivorous aquatic plants dying down to turions (resting buds) in winter. Stems green to greenish-yellow, 400 mm or more long, filiform, sparingly branched. Leaves submerged, numerous, green to greenish-yellow, multifid 30-40 mm long, segments capillary up to 10 mm long. Bladders numerous and conspicuous, 1-4 mm long when mature, obliquely ovoid, mouth with 2 long setae, whole structure coloured dark blue to purple when mature and attached by short stalk near base of leaf segments. Inflorescence rarely seen, when present borne on a dark-green 2-4(-5)-flowered scape up to 170 mm long, this broad at base and tapering. Calyx lobes oblong to ellpitic. Flowers dark yellow sometimes with a dark orange blotch on palate. Corolla upper lip 3-lobed, lower entire, 7-9 mm wide, broad, palate protruded; spur short, obtuse. Capsule 1.5-2 mm diameter, globose. Seeds not known in New Zealand.
Similar taxa
Utricularia gibba L. is an introduced species that has smaller, less divided floating stems and entire leaves. The upper lip of the corolla in this species is entire rather than 3-lobed as is seen in U. australis. U. gibba forms massive mats floating at the water surface and is usually always flowering while U. australis produces feathery, wholly submerged, floating stems and is very rarely found flowering. New Zealand examples of the naturalised U. geminiscapa Benj. differ from U. australis by their terminal leaves bearing small hairs, the internal portions of their bladders bearing bearing quadrifid trichomes whose arms are in parallel, and by their cleistogamous flowering condition. Utricularia australis could be confused with the fully submerged, aquatic state of Myriophyllum propinquum A.Cunn., with which it sometimes grows. However, Myriophyllum can be readily distinguished from U. australis because it bears roots and the foliage lacks bladders
Flowering
Flowers, December-March(-April), though some populations may never flower.
Flower colours
Orange, Yellow
Fruiting
Seed has not yet been seen in New Zealand plants.
Propagation technique
Difficult and should not be removed from the wild.
Threats
Now seriously at risk throughout most of its northern North Island range through competition from Utricularia gibba which occupies the same habitat and has a more aggressive growth form and also by other introduced aquatic weeds. It is also vulnerable to habitat loss through modification and drainage. There is some evidence which suggests it is selectively browsed by Canadian Geese and Black Swans
Etymology
utricularia: A small bladder
australis: Southern
Where To Buy
Not commericially available.
Attribution
Fact Sheet prepared by P.J. de Lange (1 November 2008). Description based on Salmon (2001), live and herbarium specimens - see also de Lange et al. (2010).
References and further reading
de Lange, P.J.; Heenan, P.B.; Norton, D.A.; Rolfe, J.R.; Sawyer, J.W.D. 2010: Threatened Plants of New Zealand. Canterbury University Press, Christchurch.
Salmon, B. 2001: Carnivorous plants of New Zealand. Ecosphere Publications, Manurewa.
Citation
Please cite as: de Lange, P.J. (Year at time of access): Utricularia australis Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/utricularia-australis/ (Date website was queried)