Ageratina riparia
Environmental Weed (2024)
Common names
mist flower
Biostatus
Exotic
Category
Vascular
Structural class
Herbs - Dicotyledonous composites
Flower colours
White
Detailed description
Erect or sprawling, many-stemmed herb to subshrub to 0.5-1.5 m. Perennial fibrous rootstock. Stems occ die back in winter, covered in purple-striped non-sticky hairs, usually purple, becoming woody, with branches in opposite pairs. Leaves in opposite pairs, 60-100 x 15-25 mm, willow-like, coarsely serrate except near base. Flowers small, white, 4-5 mm diam, in terminal clusters, Aug-Jan. Seeds black, 5-angled, 2 mm long.
Similar taxa
Distinctive toothed leaves separate mistflower from Mexican devil
Habitat
Terrestrial. Humid subtropical and tropical rainforests (W.T. Parsons & E.G. Cuthbertson 2001). In NZ, coastal, lowland (Timmins & MacKenzie 1995). Forest margin, damp banks and streamsides, slips (Timmins & MacKenzie 1995). In Australia, shaded riverbanks, steep south facing hillsides in areas where annual rainfall exceeds 1700mm (W.T. Parsons & E.G. Cuthbertson 2001).
Conservation status
Not applicable
Detailed taxonomy
Family
Ecology
Flowering
August, September, October, November, December, January, February, March
Fruiting
June-September (W.T. Parsons & E.G. Cuthbertson 2001)
Year naturalised
1931
Origin
Mexico, W. Indies
Reason for introduction
Ornamental
Tolerances
Tolerant of deep shade and damp, damage and grazing, salt, most soils
Life cycle and dispersal
Perennial. Reproduces by seed. Plants may re-grow following disturbance if roots (occasionally stems) contact ground. Drooping stems can layer in wet sites. Dispersed by wind, water, road mowing machines (Timmins & MacKenzie 1995). Many seeds produced (ibid.)
Other information
Etymology
riparia: From the Latin ripa ‘streambank or ‘riverbank’ and the suffix -aris which gives the sense ‘belonging to’ or ’ resembling’. Riparia means growing on the banks of streams or rivers
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.
AGERIP