Answer: Your question points out the problems of using common names versus Latin names. Common names can vary widely from one part of the country to another. When you call a plant "common nightshade" I really don't have any way to determine exactly what you have because nightshade is used commonly for two different poisonous plants: Solanum dulcamara and Atropa belladonna. I'll provide a description of each, but if you are concerned, you might want to look them up in a plant book with photos or take a sample of what you have to your County Cooperative Extension office.
Atropa belladonna is a tall perennial with branched stems and ovate leaves up to 8 inches long. Purple-brown, bell-shaped flowers show up during summer, and are followed by shiny black berries. Total height is 3-5 feet. It's toxic if eaten and a skin irritant and possible allergen.
Solanum dulcamara is shrublike, often climbing or trailing perennial with green stems and ovate pointed leaves. Violet to blue or white flowers are in clusters in summer, followed by ovoid bright red berries. Height up to 12 feet. All parts are toxic if eaten.
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