American nightshade (Solanum americanum) belongs to the Solanaceae (the Nightshade family). It is an annual herb that is native to North America, and introduced into Japan after World War 2. This herb occurs in forest edges and fields, much-branched and can reach 20-30 cm in height. During July to September, pale purple to white flowers are seen. This herb looks like black nightshade, but varies according to slender stem, narrower leaf and glossy fruit.