Rorippa microphylla (Boenn.) N. Hylander
Vascular – Exotic
Herbs - Dicotyledons other than Composites
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.
A bright green, robust, creeping or upright herb that has small white flowers in spring through summer, and is found along the margins of slow flowing shallow waters. Leaves have a distinctive peppery smell when crushed.
Common throughout New Zealand.
Margins of slow moving rivers, streams, ditches and drains.
Wetland plant indicator status rating
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Perennial stoloniferous herb. Stems trailing, glabrous, to several m long. Leaves glabrous, all similar, but becoming smaller near inflorescence. Pinnate, petiolate, 2-10-(25) x 1-5 cm; basal auricles very small; leaflets rounded, ovate; margins entire or sinuate. Pedicels glabrous, slender, erecto-patent, spreading to deflexed at fruiting, (8)-12-20-(30) mm long. Sepals 2.5-3.5 x 1 mm. Petals white, (4)-5-6 x 1.5-2.5 mm. Silique glabrous, narrow-oblong to linear, curved, (10)-15-25-(30) x c.1.5 mm; valves with distinct midrib, at least below; style c. 1 mm long. Seeds in ± 1 row per locule, brown, c. 1mm long, coarsely reticulate with 100-150 polygonal depressions per face.
Very similar to N. officinale, but the flowers of N. microphyllum are larger, capsules are longer and more slender, and the seeds are in one row and with more finely pitted surfaces. The leaves of N. microphyllum turn brown/purple in autumn/winter.
August - June
Stem fragmentation and seed.
Reason for introduction
microphyllum: Small leaf
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA). Features description from Webb et al. (1988).
References and further reading
Popay et al (2010). An illustrated guide to common weeds of New Zealand, third edition. NZ Plant Protection Society Inc, 416pp.
Johnson PN, Brooke PA (1989). Wetland plants in New Zealand. DSIR Field Guide, DSIR Publishing, Wellington. 319pp.
Aston, H (1977). Aquatic plants of Australia. Melbourne University Press, 367pp.
Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. (1988). Flora of New Zealand Volume 4: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.