Scientific name: Phytolacca octandra
- Tall, many-branched, upright bush to 2 m high
- Bluntly pointed, elliptical leaves (15 x 5 cm)
- Small, whitish flowers clustered around an upright stem up to 7 cm long
- Fruits are distinctive small black berries when ripe (8 mm diameter), tightly clustered around the stem.
- Native to the mountains of Central and tropical South America and introduced to New Zealand around 1867.
- Inkweed is predominantly a weed of broken and hill country (i.e. with many bare areas) where it is found adjacent to fence lines, stock tracks, slips, cut-over scrub and waste areas. It is common to and locally abundant in the mostly frost-free areas of the north and west of both North and South Islands.
- Inkweed is a soft wooded, perennial shrub living for about 10 years before it slowly dies. Flowering is from November to August with many whitish or pale green flowers arranged around an upright stem. Fruit are 8 mm berries tightly clustered around the stem and ripening from green to red to black. Each fruit contains 8 black, roundish seeds (2-2.5 mm diameter)
- Seeds are primarily dispersed by birds which explains the appearance of plants along fence lines and other roosts.
- The ripe fruits can be crushed to produce a dark purple dye or ink
- The roots have been used for medicinal purposes
- Plants are not eaten by stock.
Impacts on pasture
- Inkweed is only a nuisance in poor, runout (i.e. weedy and poorly performing) pastures or in scrubby, broken hill country (i.e. with lots of bare areas)
- When present in pasture, inkweed may restrict grazing and result in reduced pasture utilisation.
Impacts on forage crops
- Inkweed may grow in fodder crops grown on rough country, but usually in very low populations that will not impact crop production.
Impacts on stock
- Toxic to livestock, with reports of death to pigs, cattle and poultry. Sheep appear to be only mildly affected
- Generally, under normal grazing pressure, inkweed is avoided by stock
- Inkweed may cause irritation of skin and eyes if handled without PPE. Ingestion of berries can lead to headaches, burning in the mouth, stomach cramps and diarrhoea.
Grazing and cultural management
- Young inkweed plants may not survive intensive mob stocking but once established they will not be grazed
- Inkweed may be controlled by mowing, however, as plants are generally found in areas not suited for this, hand grubbing can be effective.
- Inkweed seedlings readily controlled by the phenoxy herbicides MCPA and 2,4-D
- Larger plants controlled with the addition of picloram, preferably applied as a spot treatment to avoid pasture damage
- May also be controlled with spot applications of metsulfuron
- Inkweed is highly susceptible to glyphosate. Wiping several leaves with a weed wiper or spraying part of the plant lightly with concentrated glyphosate is usually sufficient to kill the plant with little or no pasture damage.
- There are no biosecurity issues with inkweed and the plant would be only rarely found in hay or silage.
- Conner H E 1977. The poisonous plants in New Zealand. E.C. Keating, Government Printer Wellington New Zealand. 247 p.
- Holden P 2021/2022. New Zealand Novachem agrichemical manual. Agrimedia Ltd, Christchurch, New Zealand. 864 p.
- Popay I, Champion P, James T 2010. An illustrated guide to common weeds of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand. 416 p.
- Breitwieser I, Brownsey PJ, Nelson WA, Smissen R, Wilton AD eds. (2010 -2021) Flora of New Zealand Online â€“ Weed Profile â€“ Phytolacca octandra L. (based on Heenan 2010). (Accessed 6 October 2021)