Black nightshade (Solanum nigrum)

Common Names: European black nightshade, common nightshade, poisonberry, garden nightshade

Description:

Black nightshade (Solanum nigrum) is a fast-growing weedy annual from Eurasia, common in gardens, farm fields, and other disturbed ground [1][2]. Its small, tomato-like berries turn from green to black as they ripen, and it's part of a group of very similar-looking nightshade species that can be genuinely difficult to tell apart even for experienced growers [2]. MISIN tracks it because every part of the plant ? especially the green, unripe berries ? contains natural compounds that are toxic to people and livestock if eaten [3][4].

Habit:

Black nightshade is a bushy annual (occasionally a short-lived perennial in frost-free areas) growing about 8 inches to 3 feet tall, with dark green, egg-shaped leaves that have smooth to slightly wavy edges [1][2]. It flowers from spring through fall, producing small clusters of 4 to 8 white, star-shaped flowers with yellow centers [2]. The clearest identification window is when the berries are present: they start out green and hard, then ripen to a dull black or purplish-black, usually a bit under a third of an inch across, hanging in small clusters [2].

At-a-glance cues:

1. Small, round berries that ripen from green to dull black or purplish-black, roughly 1/5 to 3/10 inch across [2]
2. Clusters of 4 to 8 small, white, star-shaped flowers with yellow centers [2]
3. Dark green, egg-shaped leaves with smooth to shallowly wavy or toothed edges, alternating up the stem [1]
4. A bushy, branching growth habit on disturbed, sunny ground ? gardens, field edges, roadsides [1]

Leaves:

1. Arrangement: alternate, on short stalks [1]
2. Shape: egg-shaped (ovate), 0.8 to 3 inches (2 to 8 cm) long [1]
3. Margin: variable ? smooth-edged to shallowly lobed or toothed, even between plants of the same population [1]
4. Surface: dark green and matte (not shiny) on both sides, smooth or finely hairy [1]

Stems:

1. Habit: sprawling to upright, herbaceous, occasionally slightly woody at the base in longer-lived plants [1]
2. Cross-section: round to angular [1]
3. Surface: smooth or sparsely hairy [1]
4. Color: green to purplish [1]

Flowers:

1. Color: white, with yellow centers [1][2]
2. Shape: small, star-shaped [1]
3. Arrangement: clusters of 4 to 8 flowers on slender stalks, about 1/5 to 1/3 inch (5 to 8 mm) across [1][2]
4. Bloom time: spring through fall (roughly March through October in mild climates) [2]

Fruit and seeds:

1. Fruit type: round berry, green when unripe, ripening to dull black or purplish-black, about 1/5 to 1/2 inch (5 to 13 mm) across [1][2]
2. Seeds: many small, flattened, finely pitted seeds per berry, yellow to dark brown [1]
3. Ripening: green and firm at first, softening and darkening as they mature [2]
4. Dispersal: birds and other wildlife eat the ripe berries and spread the seeds in their droppings; seeds can also travel in contaminated crop seed, on equipment, or in soil [1]

Habitat:

Black nightshade is native to Eurasia and has spread widely across North America [1]. It grows readily in orchards, vineyards, crop fields, pastures, gardens, yards, and other disturbed, sunny ground, thriving anywhere soil has been recently turned or cultivated [1].

Reproduction:

Black nightshade spreads only by seed, and it produces an enormous number of them ? commonly reported in the range of tens of thousands to nearly 800,000 seeds from a single, well-grown plant [5]. Those seeds most often arrive on a property in contaminated garden soil, compost, or crop seed, or get carried in by birds that have eaten the ripe berries elsewhere [1][5]. Seeds can also remain viable in the soil for many years ? some studies report decades ? so a patch pulled today can keep resurfacing from the seed bank for years afterward [5].

As a summer annual, black nightshade germinates, flowers, and sets seed within a single growing season, so removing plants before they flower (rather than after berries have already formed) is the most effective way to keep a patch from adding to that seed bank.

Impact and Damage:

Every part of black nightshade contains natural compounds called glycoalkaloids, and the unripe green berries and leaves carry the highest concentrations [3][4]. Eating them can cause nausea, vomiting, diarrhea, and stomach cramps, with more severe poisoning affecting the heart and nervous system; the same risk applies to dogs, cats, and grazing livestock [3][4]. In 2024, a real-world case in the Netherlands showed how easily this risk can slip past notice: black nightshade berries that had been growing among a crop of green beans were accidentally harvested and packaged together, and several people who ate the contaminated frozen beans needed emergency-department evaluation before recovering with only minor symptoms [4]. That case is a useful reminder for home gardeners too ? if black nightshade has been growing among beans, peas, or other produce you're about to harvest and freeze or can, it's worth checking carefully for its berries first.

In gardens and farm fields, black nightshade competes with vegetables and row crops for water, light, and nutrients, and its berries are notorious for contaminating harvested crops like dry beans and peas ? the berries are similar enough in size and color to slip through sorting and processing right along with the crop, reducing its quality and value [5]. It also serves as a host for pests and diseases that affect closely related garden crops such as tomatoes, potatoes, and peppers, giving it an outsized impact for a plant that's often overlooked as just another garden weed [2].

Similar species:

American black nightshade (Solanum americanum) is black nightshade's closest match and part of the same confusing group of look-alike nightshades ? the two are difficult to separate reliably without close examination of the flowers and berries, and even experienced botanists sometimes disagree on which is which in a given population.

Hairy nightshade (Solanum physalifolium) looks similar but is distinguished by its noticeably hairy stems and leaves, compared to black nightshade's smooth to only sparsely hairy surfaces.

Horsenettle (Solanum carolinense) is easily told apart once it's flowering or fruiting ? its flowers are pale violet rather than white, and its stems carry short, sharp spines that black nightshade lacks entirely.

Silverleaf nightshade (Solanum elaeagnifolium) stands out for its silvery-gray, felted leaves and stems, quite different from black nightshade's plain dark green foliage, along with violet-blue (rather than white) flowers.

Monitoring and rapid response:

Signs to watch for:

1. A bushy weed with dark green, egg-shaped leaves and small white, star-shaped flowers in garden beds or field edges, spring through fall
2. Small green berries ripening to dull black ? check carefully among beans, peas, or other low crops before harvest, especially if this weed has been growing nearby [4]
3. Any wilting, vomiting, or other signs of illness in a pet or grazing animal that has had access to an area with this plant

What you can do:

1. Hand-pull or hoe young plants before they flower ? this is both the easiest removal window and the one that keeps the most seed out of the soil
2. Wear gloves, since the berries and foliage contain toxic compounds
3. Bag and trash pulled plants that already have berries, rather than composting them, since seeds can survive and remain viable in compost
4. Before harvesting beans, peas, or other low-growing produce, walk the rows and remove any black nightshade plants and their berries first
5. Because seeds can persist in the soil for years, plan on repeat monitoring and removal over multiple seasons rather than a single cleanup
6. Natural-area and farm crews: prioritize field edges and disturbed ground where new patches are most likely to establish, and rotate crops or cultivate between plantings to disrupt the seed bank at a larger scale

When to call a professional:

1. Large infestations across crop fields or pastures where hand removal isn't practical
2. Suspected poisoning in a pet or livestock animal ? this is a veterinary emergency, not a plant-management question, so contact a veterinarian right away
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. University of California Statewide IPM Program (UC IPM). Black Nightshade, Weeds Identification Gallery. ipm.ucanr.edu
2. University of California Statewide IPM Program (UC IPM). Black Nightshade, Weed Gallery (identification detail). ipm.ucanr.edu
3. ScienceDirect Topics (summarizing peer-reviewed toxicology literature). Solanine ? glycoalkaloid mechanism and dose-response in mammals.
4. Roelen CCJ, Mulder-Spijkerboer HN, Gee ESI, Kolukirik P, et al. (2024). "Public health risk due to contamination of Solanum nigrum in frozen green beans ? collaboration effort between a poison centre, a hospital and health authorities." Clinical Toxicology 62(2):126?128. semanticscholar.org
5. UC IPM Weed Gallery / general agronomic literature on Solanum nigrum seed production, longevity, and crop-contamination impacts (reproduction and economic-impact figures).

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