Species

Nasturtium microphyllum

Etymology

microphyllum: small leaf

Common Name(s)

one-rowed watercress

Authority

Nasturtium microphyllum Boenn. ex Rchb.

Family

Brassicaceae

Brief Description

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.

Flora Category

Vascular - Exotic

NVS Species Code

NASMIC

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.

Structural Class

Dicotyledonous Herbs other than Composites

Synonyms

Rorippa microphylla (Boenn.) N. Hylander

Distribution

Common throughout New Zealand.

Habitat

Margins of slow moving rivers, streams, ditches and drains.

Features

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.

Similar Taxa

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.

Flowering

August - June

Flower Colours

White

Fruiting

Summer-autumn

Year Naturalised

1954

Origin

Europe

Reason for Introduction

Culinary herb.

Life Cycle and Dispersal

Stem fragmentation and seed.

Attribution

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.

This page last updated on 30 Jul 2014