Woolly nightshade

Scientific name: Solanum mauritianum

woolly nightshade flowers

woolly nightshade flowers

woolly nightshade fruit

woolly nightshade

woolly nightshade plant

woolly nightshade tree

woolly nightshade tree

woolly nightshade underside leaf

woolly nightshade young plant

woolly nightshade young plant

woolly nightshade
  • Key characteristics
  • Biology
  • Impacts
  • Control
  • Further information

  • Strong-growing small tree, to approximately 10 m tall, with large greyish leaves. Often growing in pure stands
  • Mauve or violet flowers about 20 mm across, in dense clusters, flowering throughout the year
  • Flowers are followed by clusters of fruit, round green berries 10-12 mm diameter that ripen to a dull yellow
  • Leaves are velvety, grey-green in colour, up to 25 cm long by 10 cm across, and narrowing at both ends. Leaves have an unpleasant smell when bruised
  • Prominent auricles (green ear-like structures) at the bases of the leaves
  • Stems are woody and covered with woolly hairs when young
  • Trunks are up to 150 mm across and branched in a Y-pattern. The plants have no spines
  • Found growing in rough pasture in gullies, next to shelter belts and bush margins, on roadsides and in poorly maintained areas
  • Common or abundant in frost-free northern New Zealand but spreading southwards. In the South Island found in Nelson City and the Tasman District
  • Believed to be poisonous to livestock.

Origin

  • Woolly nightshade came originally from southern Brazil and Uruguay
  • Most likely introduced in New Zealand as a garden plant but soon escaped and was found naturalised as early as the 1880s
  • Also introduced and more or less invasive in Australia, South Africa and many Pacific islands.

Life cycle

  • Seed production is copious and the seeds are initially dormant and need a period of after-ripening at alternating temperatures before they can germinate
  • The seeds are eaten by birds and often spread by them
  • Plants have deep tap roots
  • Seeds can lie dormant in the soil for 20-30 years.

Impact on humans

  • Berries of woolly nightshade can be toxic to children
  • Hairy leaves may induce itching and in a confined space the smell is unpleasant and may lead to headaches.

Impact on pasture

  • Woolly nightshade can have allelopathic effects on other plant species
  • Although it grows in less well-maintained grassland, it can reduce the amount of useful vegetation available to livestock.

Impact on livestock

  • Woolly nightshade is thought to be poisonous to livestock

 

  • The species is listed on the National Pest Plant Accord 2012, an agreement between the Nursery and Garden Industry Association, Central Government and regional councils that means that plants of woolly nightshade and several other species cannot be grown, distributed, displayed or sold.

Pasture species/cultivars

  • Dense, vigorous pastures help prevent woolly nightshade and other weedy species from establishing, restricting their growth and survival
  • Grass species or cultivars appropriate to the district and infected with the right endophytes should help
  • In areas where cocksfoot grows well it could be a better competitor than ryegrass.

Physical control

  • Young plants up to about 600 mm tall can be pulled out, the roots shaken to remove soil and the plants left to die
  • Plants that are cut down must have the stumps treated with herbicide or they will regrow.

Chemical control

  • Cut stump treatment: cut the trunk to within 50 mm of the ground and paint an appropriate herbicide mixture over the top and sides of the stump
  • Basal treatment of trunk: using an appropriate herbicide such as X-tree Basal, liberally paint or spray the trunk from ground level up to about 6x the diameter, making sure the entire trunk is covered
  • Spray application: totally cover all leaf surfaces with a picloram containing herbicide. More suitable for small plants but larger plants may be treated but care should be taken to minimise overspray and collateral damage
  • Prill application: similarly small plants can be effectively controlled with an application of picloram prills at the base of the plant.

Herbicides that can be used

Herbicide common name Application method
glyphosate Stump swabbing
picloram gel Stump swabbing
picloram prills Spread over soil
triclopyr Stump swabbing, trunk base treatment.
triclopyr/picloram mix Stump swabbing, foliar spray application.
X-tree Basal Stump swabbing, trunk base treatment.

 

  • Great care must be taken with all herbicide applications as these herbicides will also kill other plants
  • Be sure to wash your hands after using chemicals of any kind
  • Consult your farm consultant, industry rep or the latest New Zealand Agrichemical Manual for more information about chemical control.

 

 

References