I grew up calling this semi-woody vine deadly nightshade, but it turns out I was technically wrong. This is bittersweet nightshade. It goes by many other names too, depending on where you live, so it is probably better to call this one by its species name, Solanum dulcamara, at least for now.
The purple flowers of bittersweet nightshade are shaped like an exploding star: the petals arch backwards and expose bright yellow stamens. The green, egg-shaped berries turn orange, and then bright red when they are ripe. The total effect of a ripening vine can be quite beautiful in summer and fall.
Bittersweet nightshade is an introduced species that is now considered invasive. It is common in riparian areas and wetlands, but also in waste areas and along roads and fencerows. All parts of the plant are moderately poisonous, but because it tastes bad, most animals will avoid eating it. (A few bird species eat the berries and disperse the seeds.)
Gardeners beware: children may be attracted to the colorful berries of nightshade and want to eat them, so ignoring this weed in the home garden could result in accidental poisoning.
Locally in Virginia, we have another plant that is commonly called “bittersweet”, but it is in a different genus altogether (Celastrus). Other common names of bittersweet nightshade include deadly nightshade, bitter nightshade, climbing nightshade, trailing nightshade and poisonberry.