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.
Mint-like plant, up to 1 m tall, with square stems, toothed paired leaves and tiny white or pale mauve flowers produced in groups above each pair of leaves in the upper stem, but no minty smell when crushed.
Abundant in the Waikato and Rotorua Lakes, few sites in Northland, Auckland and in Westland near Haast.
Lake and river margins, drains and swamps, often growing at the base of raupo and tall sedges.
Wetland plant indicator status rating
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Perennial herb. Stem hairy, to c. 1 m tall. Lvs shortly petiolate or sessile. Lamina 3-8.5 × 1-3 cm, ovate-lanceolate to elliptic, deeply crenate-serrate, hairy at first, becoming glabrous or nearly so; basal area with narrow-oblong or linear-oblong lobes extending to midrib; apex ± acuminate. Upper lvs and bracts smaller, without basal lobes, hairy, especially on veins below. Calyx c. 3 mm long, hairy; teeth > tube, lanceolate-acuminate. Corolla 3.5-4 mm long, white with purple spots on lower lip and in throat. Nutlets 1.2-1.3 mm long, broad-obovoid, glandular and swollen on anterior face, with margin clearly delimited.
Superficially similar to mints (Mentha spp.) but lacking the characteristic smell of those plants.
Summer and autumn
Purple, Red/Pink, White
Summer and autumn
Seed dispersed by water, footwear or contaminated machinery.
Europe, cold temperate Asia
Reason for introduction
Possibly as a herbal plant
Rarely controlled, but can be controlled manually, mechanically or herbicidally depending on situation.
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA). Features description from Webb et al., (1988).
References and further reading
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.
Johnson PN, Brooke PA (1989). Wetland plants in New Zealand. DSIR Field Guide, DSIR Publishing, Wellington. 319pp.
Champion et al (2012). Freshwater Pests of New Zealand. NIWA publication. http://www.niwa.co.nz/freshwater-and-estuaries/management-tools/identification-guides-and-fact-sheets/freshwater-pest-species