Petunia

Large white petunia is the wild South American species behind the garden petunia: a loose, spreading annual or tender perennial in the nightshade family (Solanaceae), native to the grasslands and rocky outcrops of Uruguay, southern Brazil, Paraguay, Bolivia and Argentina. Its pure white, funnel-shaped trumpets, 1 to 3 inches long, are the only white flowers in the genus, and they release a strong scent at night that draws hawkmoths. The garden petunia (Petunia x atkinsiana) is a hybrid of this species and Petunia integrifolia, but grown as itself it is a taller, looser, fragrant plant for the evening garden rather than a compact bedding mound. It is frost-tender: the RHS rates it H3, half-hardy to a winter minimum of 23°F to 34°F, which the RHS equates to USDA zones 9b/10a, so it lives through the winter outdoors only in mild gardens and is grown from seed as a warm-season annual below zone 9b.

The garden petunia is a complex Brazilian-derived hybrid in the nightshade family, grown almost everywhere as a warm-season bedding annual for its funnel-shaped, often fragrant flowers in nearly every color except true brown and black. Missouri Botanical Garden ranks it second only to impatiens in annual bedding-plant sales, prized for non-stop bloom from late spring until frost. It is a tender perennial hardy only in USDA Zones 10-11, so most of North America treats it as a single-season annual.