Black nightshade (or blackberry nightshade) Solanum nigrum is a highly adaptable plant, and a common weed across Australia, from the south to the tropical north. The species can look quite different from region to region. It produces small edible fruits throughout the year (depending on the region.) Black nightshade has often been confused with deadly nightshade Atropa belladonna: although the berries look similar, those of black nightshade bunch, while deadly nightshade has single berries along its branches. Deadly nightshade contains very toxic tropane alkaloids; it hasn’t naturalised in Australia.
As with many nightshades, eating too much of the unripened fruit can cause stomach upset. And as with nightshades (such as potatoes, eggplants, kangaroo apples and tomatoes), there have been questions about edibility by humans: tomatoes were considered toxic up until the 18th century. But despite all the concern, black nightshade produces forageable berries (when ripe) and leaves (when cooked) which have been, and are still, used in many parts of the world for a variety of culinary and medicinal purposes (although no longer for internal use in western medicine because of variable chemistry and toxicity).