Impatiens glandulifera
Environmental Weed (2024)
Common names
Himalayan balsam
Biostatus
Exotic
Category
Vascular
Structural class
Herbs - Dicotyledons other than Composites
Simplified description
Tall leafy herb dying overwinter and re-establishing from seed the following spring, up to 2.5 m tall, with thick succulent, often red-coloured angular or round stems, hollow stems, leaves in pairs or threes up to 20 cm long with a long pointed tip and finely toothed, leaves have distinctive unpleasant smell when crushed, flowers showy, purplish pink or occasionally white, up to 4 cm long in large flower heads of up to 10 long stalked flowers.
Flower colours
Red/Pink, Violet/Purple, White
Detailed description
Annual, glabrous herb; stems erect, single but branched above, to c. 2.5 m high, succulent, ribbed, swollen at nodes. Petioles to c. 8 cm long, pink above, narrowly winged, with scattered purplish elongated glands in distal 1/2. Lvs opposite or in whorls of c. 3. Lamina 10-20 × 3-8 cm, lanceolate to ovate, sharply serrate; veins impressed above, raised below; base cuneate or attenuate; apex acuminate. Fls in diffuse cymes in upper lf axils of branches, shining. Bracts and lateral sepals 5-10 mm long, ovate, pink, acuminate. Posterior sepal forming large backwards projecting hood 2.2-3 cm long (excluding spur), pink or rose with dark spots inside; spur 5-7 mm long, rather stout, green. Corolla 2-lipped, white or pale pink; uppermost petal 1.5-2 cm long, subreniform; apex truncate to slightly emarginate; lateral petals very asymmetric, c. 3.5 cm long when stretched out, sharply bent in middle with lower halves forming a circular orifice enclosing the elongated anther mass. Anthers yellow. Capsule 2-3 cm long, usually purplish on exposed side, constricted in upper 1/2, with 5 acute ridges. Seed 3.5-5 mm long, ± broadly ovoid, shining black, with a single ridge down 1 side; base truncate; apex slightly beaked.
Similar taxa
Unlikely to be mistaken for any other plant.
Distribution
Local and scattered throughout including Stewart Island, common in parts of Westland and in the vicinity of several North Island urban centres.
Habitat
Margins of water bodies, especially gullies, wet roadsides and forest margins.
Conservation status
Not applicable
Detailed taxonomy
Genus
Family
Ecology
Flowering
November to March
Fruiting
November to March
Year naturalised
1909
Origin
Himalayas
Reason for introduction
Ornamental plant
Control techniques
Rarely controlled, but can be controlled manually, mechanically or herbicidally depending on situation.
Life cycle and dispersal
Seed dispersed by water and contaminated machinery, garden discards. Seed capsule 2-3 cm long, usually purplish on exposed side, constricted in upper 1/2 with 5 acute ridges. Seed 3.5-5 mm long, more or less broadly ovoid, shining black, with a single ridge down one side; base truncate; apex slightly beaked. (Webb et al 1988)
Other information
Etymology
impatiens: From the Latin impatiens ‘impatient, hasty’, referring perhaps to the manner in which the pods of some species explode (Johnson and Smith, 1986).
Environmental Weed (2024)
This plant is named in a list of 386 environmental weeds in New Zealand 2024 prepared by DOC. 759 candidate species were considered for inclusion on this new comprehensive list of environmental weeds in New Zealand. The species considered were drawn from published lists of weed species, lists of plants that must be reported or managed by law if observed, existing national and regional programmes and agreements for pest management, and species already managed by the Department of Conservation (DOC). Candidate species were then assessed to see if they were fully naturalised and whether they have more than minor impacts in natural ecosystems. Read the full report here.
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.
IMPGLA
Referencing and citations
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.
Popay et al (2010). An illustrated guide to common weeds of New Zealand, third edition. NZ Plant Protection Society Inc, 416pp.
Clapham, A.R.; Tutin, T.G.; Warburg, E.F. (1962). Flora of the British Isles. Cambridge University Press, Second Edition. 1269pp.
Johnson, A. T. and Smith, H. A (1986). Plant Names Simplified: Their pronunciation, derivation and meaning. Landsman Bookshop Ltd: Buckenhill, UK.
Attribution
Factsheets prepared by Paul Champion and Deborah Hofstra (NIWA). Features description from Webb et al., (1988).