Cardamine lacustris
Common name
Iti
Synonyms
Iti lacustris Garn.-Jones et P.N.Johnson
Family
Brassicaceae
Flora category
Vascular – Native
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Structural class
Dicotyledonous Herbs other than Composites
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
CARLCT
Chromosome number
2n = 48
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 | At Risk – Naturally Uncommon | Qualifiers: Sp
Previous conservation statuses
2009 | At Risk – Naturally Uncommon | Qualifiers: EF
2004 | Range Restricted
Distribution
Endemic. New Zealand: South Island (Lakes Manapouri, Te Anau and also around small tarns in the eastern part of Fiordland)
Habitat
A lake and tarn dwelling plant. It mostly grows on gently-shelving slopes usually within a sparse turf of other plants where a thin cover of silt or fine sand is lodged among firm and stable cobbles or gravels. In its main lake habitats these are sites which tend to be neither the most sheltered nor the most exposed available, but are subject to moderate wave action and the resultant periodic disturbance of sediments.
Features
Minute ephemeral or annual rosette herb. Stems on young plants very short, on older plants lateral, ascending at first, later prostrate, geniculate, rooting regularly, up to 50 mm long, reaching 0.8-2.0 mm diameter, glabrous or sometimes with sparse, fine, slightly recurved hairs. Leaves glabrous, or with sparse simple hairs on petiole, slightly glossy, dull green or tinged purplish-grey, in rosettes and clustered on stems. Early rosette leaves entire, linear-spathulate; later rosette and cauline leaves pinnatifid, 20-50 mm long; petiole 2-12 mm long, 0.5-1.0 mm wide; terminal lobe narrow-spathulate, 2-5 mm broad; lateral lobes narrowly oblong-spathulate, 4-10 mm long, sometimes single or in uneven numbers, but usually in l-3 subopposite pairs. Peduncle glabrous, 1-2 mm long, reaching 2-5 mm long at fruiting. Sepals suberect, oblong, glabrous, green with narrow pale margins, 1.5-2.0 × 0.6-1.0 mm. Petals white, suberect, oblong- to obovate-spathulate, obtuse, 1.8-2.5 × 0.8-1.2 mm, weakly clawed; limb spreading. Stamens suberect; median stamens usually 2, rarely 4, 1.6-2.0 mm long; lateral stamens 1.0-1.5 mm long. Ovary ellipsoid, 1.0-1.6 mm long; stigma sessile, 0.4 mm diameter; locules each with 5-8 ovules. Silicle elliptic to oblong, l.0-3.5 × 1.0-1.7 mm; valves pale straw coloured, thin, convex, glabrous, not veined or with 1 weak vein. Seeds c.5-8 in one row in each locule, pale to reddish brown, oblong, c.1 mm long.
Similar taxa
Cardamine lacustris is probably closely allied to an undescribed Cardamine (known by the tag name - tarn), which inhabits the moist margins of tarns, kettles, and streams from Marlborough south through inland Canterbury to Otago and northern Southland. This unnamed cress has a similar over all size and leaf shape to C. lacustris but differs by the long peduncles and a narrow, explosively dehiscent silique 10-15 times as long as its width.
Flowering
October - May (depends on water levels)
Flower colours
White
Fruiting
November - July (depends on water levels)
Life cycle
Seeds are dispersed by ballistic projection, water and attachment (Thorsen et al., 2009).
Propagation technique
Easily grown from fresh seed. Plants do best kept in a small pot partially submerged in water. Not that attractive for the garden but the leaves are edible and it could be used in cress sandwiches.
Threats
Apparently not threatened but not that common either. Its presence is dictated by seasonal water levels. Some populations around Lake Manapuri and Te Anau may be threatened. Further research is required.
Etymology
cardamine: From the Greek name kárdamon, referring to an Indian spice
lacustris: From the Latin lacus ‘lake’, meaning growing beside a lake
Where To Buy
Not commercially available
Attribution
Description from Garnock-Jones and Johnson (1987)
References and further reading
Garnock-Jones, P.J.; Johnson, P.N. 1987: Iti lacustris (Brassicaceae), a new genus and species from southern New Zealand. New Zealand Journal of Botany 25: 603-610 , where in the species was initially described as a segregate genus Iti
Thorsen, M. J.; Dickinson, K. J. M.; Seddon, P. J. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 2009 Vol. 11 No. 4 pp. 285-309