nicotiana, any plant of the genus Nicotiana of the family Solanaceae (nightshade family). Most species are herbs native to tropical America, although there are a few North American species and several others in the S Pacific, Australia and SW Africa. Many are cultivated for their fragrant trumpet-shaped flowers, which usually open at night. Commercial tobacco is obtained chiefly from the leaves of Nicotiana tabacum. The smaller plant cultivated and smoked by Native Americans of E United States before the arrival of white men is N. rustica. It and other nicotianas are used for making insecticides as well as for smoking. Nicotiana is classified in the division Magnoliophyta, class Magnoliopsida, order Polemoniales, family Solanaceae.