Asteraceae (daisy) family
Also known as
eupatorium, Eupatorium adenophorum, Eupatorium glandulosum
Where is it originally from?
What does it look like?
Erect, many-stemmed herb to subshrub to 1-2 m with a perennial fibrous rootstock. Stems often die back in winter, are densely covered in stalked sticky hairs, are usually purple, become woody with age, have branches in opposite pairs, and often have galls which are formed by a parasitic fly. Diamond-shaped leaves (55-80 x 35-70 mm) with irregularly round-toothed edges are in opposite pairs along the stems. From August to December dense clusters of small, white flowers (5-7 mm diameter) are produced, followed by 5-angled black seeds (1.8 mm long).
Are there any similar species?
Mistflower (A. riparia) is similar. Alternatives: Try the native parataniwha (Elatostema rugosum) or kakaha (Astelia fragrans) or non-native winter roses (Helleborus species). Your local garden centre will be able to recommend other non-weedy alternatives that will grow well in your area.
Why is it weedy?
Dense habit, overtops groundcovers and small shrubs, long-lived, quick maturing, and produces many highly viable, well dispersed (probably short-lived) seed. Drooping stems can take root where they touch the ground. Toxic, so usually shunned by livestock. Tolerant of moderate shade, damage and grazing, salt, most soils, drought and damp. It invades rough pastureland, strips of land along waterways, wetlands and roadsides.
How does it spread?
Seed travels a long distance by wind and is also spread in water. Common seed sources include infestations on roadsides, in quarries, plantation forest, and rough pasture.
What damage does it do?
Forms dense colonies, preventing the seedlings of native species from establishing in a wide range of habitats. Invades strips of land on the margins of waterbodies, replacing vulnerable species, and can impede water flow in swamps, causing flooding.
Which habitats is it likely to invade?
Lightly shaded frost-free areas: forest edges, shrublands, wetlands, streamsides, open forest, inshore and offshore islands, gumlands, slips, alluvial flats, coast and estuaries.
What can I do to get rid of it?
1. Dig or pull out small infestations. Expose roots.
2. Spray: glyphosate (20ml/L + penetrant).
3. Spray: metsulfuron-methyl 600g/kg (20g/100L (spraygun) or 5g/10L (knapsack)). Add penetrant in winter. Spray lightly, not to run off.
What can I do to stop it coming back?
Permanently exclude livestock and control vertebrate pests to allow native species to provide competition for this weed. Interplanting with taller, shade-loving species can help in shady areas, but in open, moderately-lit sites, continuing control will be needed. In low-growing habitats, dense groundcover planting may be necessary. Minimise disturbance as seed bank reinfests bared areas.