A volunteer seedling comes up next to the tomato bed. The easy assumption is that it dropped from last year’s fruit.
Sometimes it did. Sometimes it is a toxic relative wearing the same disguise.
Three weeds cause most of the confusion: horsenettle, black nightshade, and bittersweet nightshade. All three belong to the same family as the garden tomato. All three carry real poisoning risk.
This guide covers how to recognize each one. Pulling the wrong seedling by hand is usually the safest mistake you can make.
The short version
Horsenettle earns the nickname wild tomato honestly. Its young berries are smooth, yellow, and shaped almost exactly like a small plum tomato. The plant itself has prickly stems and smells like potato when crushed.
Black nightshade looks less like a tomato itself. Its sprawling habit and small berries still confuse new gardeners early in the season.
Bittersweet nightshade is the outlier, a climbing vine with flowers that closely resemble a tomato blossom. All three are toxic to some degree, and common enough that most home gardeners will eventually pull one.
Horsenettle: the plant literally called wild tomato
Solanum carolinense goes by several common names, and wild tomato is one of the most telling. The plant grows one to four feet tall, erect or sprawling, with prickles running along both stems and leaves.
Young berries are smooth skinned. They genuinely resemble small, plump, yellow tomatoes. As they mature, they turn yellow and wrinkle, losing the resemblance fast.
Crushed foliage gives away the family connection immediately. It carries the distinct odor of a potato, since horsenettle and potato share the same genus, Solanum.
The plant is dangerous, not just a nuisance. All parts are poisonous, with mature berries carrying the highest concentration of solanine. A documented child fatality in Philadelphia is on record from eating the fruit.
Poisoning symptoms include nausea, vomiting, and in severe cases, respiratory depression. Horsenettle also spreads aggressively.
A single plant can produce up to 5,000 seeds. Its roots run as deep as 10 feet, regenerating new plants from any fragment left behind by tilling.
Black nightshade: sprawling and easy to miss early
Solanum americanum grows as an annual or short lived perennial. It reaches up to four feet with an upright, herbaceous habit, showing up as a weed in gardens, thickets, and disturbed soil across most of the country.
Unlike horsenettle, its berries do not look much like a tomato. They start green with white flecks and ripen to shiny black or blackish purple. Each one measures smaller than a quarter inch across.
The confusion tends to happen earlier, at the seedling and young plant stage. The sprawling growth habit and simple leaves can pass for a stray tomato volunteer before any fruit forms.
Every part of the plant is potentially toxic to humans and pets. Leaves and berries carry the most risk.
Bittersweet nightshade: the climbing cousin
Solanum dulcamara breaks the pattern of the other two by climbing rather than sprawling. It is a trailing to climbing vine, with stems that can reach up to 10 feet and often a woody, purplish base.
The leaves are dark green and heart shaped at the base, lobed higher up the plant. That is distinct from a tomato’s evenly compound foliage.
What gives the family connection away is the flower. Its star shaped purple blooms, with yellow centers, closely resemble tomato and potato blossoms, a detail that surprises gardeners who assume the resemblance stops at the leaves.
The berries ripen from green to bright red. They are toxic if eaten in enough quantity, a particular hazard for curious children drawn to their color.
Why the resemblance is not a coincidence
All three weeds sit in the genus Solanum or the wider nightshade family Solanaceae. That is the same family that holds the cultivated tomato, potato, pepper, and eggplant.
Shared ancestry is exactly why the flowers, foliage, and even fruit shape echo each other so closely. It is also why caution matters more here than with an ordinary weed.
A dandelion mistaken for something else is a minor annoyance. A horsenettle berry mistaken for a volunteer cherry tomato is a genuine poisoning risk, especially for a child or pet in the garden unsupervised.
For the cultivated relatives that cause the same confusion at the seedling stage, see this site’s guide to plants that look like tomatoes at https://knowtomato.com/plants-that-look-like-tomatoes/.
Frequently asked questions
What weed is actually called wild tomato?
Horsenettle, Solanum carolinense. Its young berries are smooth, yellow, and shaped like small plum tomatoes, and crushed leaves smell like potato.
Are weeds that look like tomatoes actually poisonous?
Yes, in most cases. Horsenettle, black nightshade, and bittersweet nightshade all contain solanine or related alkaloids, concentrated most heavily in the ripe berries.
How do you tell horsenettle from a volunteer tomato seedling?
Check the stem for prickles, which no tomato plant has. Crush a leaf to smell for potato rather than the sharp scent of tomato.
Horsenettle berries also stay smooth and yellow rather than reddening the way a ripening tomato does.
What does bittersweet nightshade look like compared to a tomato?
It climbs rather than sprawls, with heart shaped leaves and purple, yellow centered flowers that closely resemble a tomato blossom. Its berries ripen from green to bright red on a vine that can reach 10 feet.
Is it safe to pull these weeds by hand?
Generally yes, with basic care. Wear gloves, avoid touching your face or eyes afterward, and keep children and pets away from the berries until the plant is fully removed and discarded.
Bottom line: most weeds that look like tomatoes turn out to be nightshade relatives, and horsenettle earns its wild tomato nickname more literally than any of them. The resemblance comes from real shared ancestry, not coincidence, which is also why the poisoning risk is real rather than exaggerated. Check for prickly stems, a potato smell, or an unusually deep taproot before assuming a volunteer seedling is a tomato, and keep the berries away from children and pets either way.
SOURCES
North Carolina State University Extension Gardener Plant Toolbox: Solanum carolinense, Horsenettle. https://plants.ces.ncsu.edu/plants/solanum-carolinense/
Ohio State University, College of Food, Agricultural, and Environmental Sciences: Horsenettle, Ohio Perennial and Biennial Weed Guide. https://weedguide.cfaes.osu.edu/singlerecord.asp?id=55
USDA Natural Resources Conservation Service: Horsenettle Plant Guide. https://www.nrcs.usda.gov/sites/default/files/2022-09/Horsenettle.pdf
North Carolina State University Extension Gardener Plant Toolbox: Solanum americanum, Black Nightshade. https://plants.ces.ncsu.edu/plants/solanum-americanum/
Washington State University Hortsense: Bittersweet Nightshade, Solanum dulcamara. https://hortsense.cahnrs.wsu.edu/fact-sheet/weeds-bittersweet-nightshade-european-bittersweet-solanum-dulcamara/