Black nightshade

Scientific name: Solanum nigrum

Black nightshade plant

Black nightshade flowering plant

Black nightshade flower

Black nightshade seedling

Black nightshade berries

Black nightshade flower
  • Key characteristics
  • Biology
  • Impacts
  • Control
  • Further information

  • A very variable annual or short-lived perennial, growing upright from a few cm tall to 75 cm high
  • Stems are green to dark purple, strong growing, often branched. They spread widely on well-grown plants and are short and spindly on stunted plants
  • Leaves are medium to dark green, oval, pointed and up to 12 cm long by 7 cm wide. Margins are entire or shallowly lobed, sometimes coarsely toothed, narrowing to the leaf stalk
  • Flowers are white or pale mauve, up to 13 mm in diameter, with five pointed petals and a central column of fused yellow anthers. Five- to 10-flowered umbel-like inflorescences are carried on stalks up to 25 mm long. Plants flower from October through to May
  • Fruits are round berries about 7-10 mm in diameter, initially green to yellowish but turning glossy black when ripe. Occasionally plants have ripe berries that are green to pale yellow
  • Black nightshade is often confused with, and sometimes called ‘deadly nightshade’. However, deadly nightshade (Atropa bella-donna) is very rare in New Zealand. Black nightshade is the plant most often referred to New Zealand’s National Poisons Information Centre.(see the article https://www.nzma.org.nz/journal/read-the-journal/all-issues/2010-2019/2012/vol-125-no-1367/article-slaughter ).It states “Black nightshade is not highly toxic and small accidental ingestions of a few berries or leaves rarely leads to symptoms. Toxicity would only be expected following ingestion of large amounts of unripe berries or other plant matter.” However, children should be advised not to eat the green unripe berries which are more poisonous than ripe black ones.

Similar species

  • Velvety nightshade (Solanum chenopodioides) is a greyish, velvety perennial, up to 1.5 m tall and with dull black berries. Mature stems have two ridges and the medium green leaves are velvety on upper and lower surfaces. It is common in shaded places and roadsides in many North Island localities and in the west of the South Island
  • Hairy nightshade (Solanum physalifolium) is a much-branched, stickily hairy, low spreading, bushy annual with round berries, 8-10 mm across, that are mottled yellow-green. The lower part of each berry is enclosed by the calyx
  • The native small-flowered nightshade (Solanum nodiflorum) has glossy black berries with a strongly reflexed (bent backwards) calyx. Smaller flowers, 5-8 mm across, are arranged on short stems, all originating from the same point (umbel-like). Found in forest, scrub and plantations, especially in coastal sites in the north of the North and South Islands, and in the Kermadecs.

Origin

  • Originally from Europe and Asia, black nightshade has been introduced to many other countries and has thrived
  • In New Zealand it was first recorded in 1853

Life cycle

  • Plants are very variable in size and can produce as many as 168,000 seeds per plant or as few as 600
  • Each berry contains an average of about 60 seeds. Little or no dormancy appears to be present in the seeds after they are separated from the berries. However, seed buried in the soil can remain dormant for many years
  • Seeds are distributed in contaminated crops or vegetable matter, and also by birds and rodents that eat the berries
  • Seeds can germinate over long periods in late spring and summer. Apparently alternating temperatures promote germination, and exposure to light can also play a role. Stratification (storage of moist seed at low temperature) can also stimulate later germination
  • Plants growing at favourable times of the year can flower within 5 to 6 weeks
  • Plants are killed by frosts, so late-germinating plants may be killed before they can set seed.

Benefits

  • Both the leaves and fruits have been used as food in some countries. Note that only fully ripe fruit should be used as under-ripe berries may be toxic.

Occurrence

  • Now abundant throughout the North and South Islands, as well as on the Kermadecs, Stewart and Chatham Islands
  • Commonly found in open places, especially on arable land, in waste places, dry river beds and roadsides. Especially common in frequently disturbed areas.

  • Black nightshade can grow quickly in summer and can be a serious competitor in some crops
  • Seeds, especially when green (and therefore more toxic), can sometimes contaminate crops such as peas
  • Can harbour insects and diseases that affect crops.

Cultural control

  • Hand weeding is effective but needs to be repeated, preferably before the plants set seed. Individual plants can be pulled out readily when young but become much harder to dislodge after branching starts.

Chemical control

  • In many cases, Solanum nigrum is readily controlled by cultivation and by most herbicides. However it is resistant to some sulphonylurea herbicides, including chlorsulfuron (e.g. Glean), commonly used in cereal crops, and to metsulfuron-methyl (e.g. Escort), used for general weed control. In these cases a second herbicide needs to be added. Black nightshade is not killed by trifluralin so other herbicides must be used
  • If triazine herbicides like simazine are regularly used in situations such as orchards, then black nightshade can develop resistance to such herbicides. If such resistance does develop, black nightshade can be killed in peas with herbicides like MCPB and bentazone, or in maize, dicamba is effective.