Black Nightshade (Solanum Nigrum) is a flowering plant of the Solanum genus, native to Eurasia and introduced into America, Australasia and South Africa. In some places, ripe berries and ripe leaves from edible strains are used as food, and plant parts are used in traditional medicine.
Black Nightshade (Solanum Nigrum) Biology
Black nightshade flowers from July to September. A plant can produces up to 400 berries each containing about 40 seeds. An average plant produces 9,000 seeds but a large plant may have 153,000. Seed from unripe berries tested 27 days after flower opening gave 100% germination. Even seed collected at just 15 days after flowering gave germination levels of 20% after a period of dry storage.
Seedling emergence begins in early May, reaches a peak in late-May or June, declines in July-August and ceases in September. Most seedlings emerge from the surface 25 mm of soil. Black nightshade grows rapidly after germination and the time from emergence to flowering is around 60 days in May and 50 days in July. The seedlings and mature plants are susceptible to frost and late-germinating seedlings are unlikely to reach maturity.
Black Nightshade (Solanum Nigrum) Occurrence
Black nightshade is a native annual found throughout most of England but becoming rarer northwards and local in Wales. It is recorded up to 1,000 ft. Black nightshade is a plentiful and troublesome weed of agricultural and horticultural fields and gardens. It occurs on a wide range of soils but prefers soil rich in nitrogen.
Black nightshade exhibits a high level of variability and several sub-species have been identified. Some populations have developed resistance to the triazine herbicide atrazine.
Black Nightshade (Solanum Nigrum) Persistence and Spread
Black nightshade seeds recovered from excavations and dated at up to 80 years old are reported to have germinated. Seeds buried for 39 years in undisturbed soil have given germination levels of over 80%. The soil temperature deeper in the soil remains relatively constant and nightshade seeds require alternating temperatures in order to germinate. Seed in cultivated soil would be expected to receive a favourable temperature regime; nevertheless, some seed is still likely to remain dormant and viable for at least 5 years. The annual decline of seeds in cultivated soil is estimated at 37%.
Small mammals disperse the fruits and seeds. Birds eat the berries and viable seeds have been found in their droppings. Black nightshade seeds have also been found in cattle droppings.
A study in Denmark has shown that the seeds can survive in silage made from sugar beet tops. In slurry heated for dry transportation, black nightshade seeds survived heating at 50°C for 15 minutes but were killed by 3 minutes at 75°C.
Black Nightshade (Solanum Nigrum) Prevention
Once eastern black nightshade has become established, prevent it from spreading into new areas. Clean seeds and berries from tillage implements and harvest equipment before using them in uninfested areas. Hay, straw, and crop seed may contain evidence of eastern black nightshade, so purchase it from a reliable source. Avoid spreading contaminated manure onto uninfested fields.
To reduce spreading, spot treat isolated patches of eastern black nightshade with an effective herbicide before the plants reach maturity. Birds have been known to eat ripe eastern black nightshade berries and transport them to uninfested fields. Spot treating with an herbicide or mowing any isolated patches in non-cropland or fallow fields can reduce the occurrence of this type of spreading.
Black Nightshade (Solanum Nigrum) General Cultural Control
The germination of eastern black nightshade is sporadic throughout the growing season, making it difficult to control in many crops; however, crop competition can aid in minimizing the plant's spread. Good cultural practices promote healthy crop stands, and the resulting canopy shading helps to control weeds. The following guidelines will help you maximize cultural control opportunities:
Follow soil test recommendations for lime and fertilizer.
Plant high-yielding varieties adapted to climate, soil, and field conditions.
If soil temperatures and conditions are optimal, plant early, using narrow row spacing and high plant populations, when possible.
Follow practical integrated pest management programs that monitor disease, insects, and weeds, and use appropriate control tactics when necessary.
Avoid certain herbicide programs (such as Classic plus Pinnacle in soybeans) that increase the potential for eastern black nightshade problems.
Mowing, plowing, disking, and cultivating are some of the more commonly used mechanical methods for field crop weed control. Existing nightshade infestations in hay crops or pastures can be controlled by timely mowing or swathing to prevent seed production. Repeated mowings may be necessary, however, due to the sporadic germination of the plant.
Fall or spring tillage can bury weed seed deeply enough that emergence is reduced. This strategy is especially effective for small-seeded weeds such as eastern black nightshade. Such tillage requires the use of a moldboard plow or other tool that will invert the soil and bury the seed. If soil erosion is a problem, however, intensive tillage may not be possible or practical. Less intensive types of tillage such as chisel plowing, disking, or field cultivating prior to planting can destroy weeds that have already emerged, but may also stimulate additional weed emergence.
Cultivating row crops removes or buries small weeds and makes them less competitive. In corn or soybeans, one or two cultivations during the first six weeks after planting helps to control weeds missed by a preemergence herbicide treatment and provides a good alternative to a postemergence herbicide application. Cultivation will not control weeds within the crop rows, and is not effective on late-germinating weeds. Studies have shown that harvesting soybeans can be difficult with as little as one nightshade plant per 10 feet of row; therefore, for soybeans, cultivation alone may not be worth the time and extra effort required.
To ensure effective, safe, and economical herbicide use, do the following:
- Select the appropriate herbicide for your weed problem and crop. The stage of weed and crop growth, temperature, soil moisture, and soil pH can affect herbicide performance. For additional information, refer to the Penn State Agronomy Guide or consult with your county extension agent or other agricultural professional.
- Read the herbicide label carefully and follow the directions. The label provides important information on safe use, application, disposal, and storage.
- Apply herbicides at the proper time.
- Apply the recommended rate to avoid injury, soil residue, or poor control.
- Calibrate application equipment several times during the season to ensure that the correct amount of herbicide is applied.
- Wear proper protective clothing when working with pesticides.
- Learn to predict weed problems. Scout fields regularly and record the types and locations of weeds present. Use field records to plan an integrated control program.
Black Nightshade (Solanum Nigrum) typically is not a major problem in corn; it is not very competitive and can be controlled easily with many common corn herbicides such as the triazine herbicides (e.g. Aatrex) or any mixtures that contain a triazine.
Black Nightshade (Solanum Nigrum) FAQ
Is Black Nightshade (Solanum Nigrum) dangerous?
Solanine levels in S. nigrum can be toxic. Children have died from poisoning after eating unripe berries. However, the plant is rarely fatal, with ripe berries causing symptoms of mild abdominal pains, vomiting, and diarrhea.The deadly nightshade lives up to its reputation once humans eat it. Ingesting just two to four berries can kill a human child. Ten to twenty berries can kill an adult.
What is the difference between deadly nightshade and black nightshade?
Black nightshade has tiny white flowers. Deadly nightshade fruit is borne singly. Deadly nightshade's calyces are prominent, like a crown or halo, extending beyond the fruit. Deadly nightshade has larger, tubular, purple or lilac flowers.
What are the signs of Black Nightshade (Solanum Nigrum) poisoning?
Delirium (agitation and confusion)
Loss of sensation.