While the term "passion flower" often serves as a blanket name for the genus *Passiflora*, it encompasses over 550 species of vines and climbers. Among these, the Maypop holds a special status as both a distinct species and one of the most well-known varieties in certain regions. The differences between *Passiflora incarnata* (Maypop) and other common passion flower varieties are rooted in their botanical characteristics, hardiness, and growth habits.
The primary difference lies in its scientific classification. The Maypop is known botanically as *Passiflora incarnata*. Other popular ornamental and fruiting varieties include the blue passion flower (*Passiflora caerulea*), the giant granadilla (*Passiflora quadrangularis*), and the widely cultivated purple passion fruit (*Passiflora edulis*). Each of these is a separate species within the same genus, meaning they share a common family (Passifloraceae) but have distinct genetic and morphological traits. *Passiflora incarnata* is native to the southeastern United States, making it uniquely indigenous to North America, whereas most other species originate from Central and South America.
Morphologically, Maypop can be distinguished by its foliage and growth structure. It features three-lobed, serrated leaves that are a deep green color, whereas other species can have vastly different leaf forms. For instance, *Passiflora caerulea* typically has five-lobed leaves, and *Passiflora quadrangularis* has very large, broad, oval leaves. Furthermore, Maypop is a herbaceous perennial, meaning its stems die back to the ground completely in winter. In contrast, many other passion flower varieties, like *P. edulis* and *P. caerulea*, are woody vines or tend to have semi-woody stems that can persist in milder climates.
All passion flowers share the complex, intricate floral structure that gives the genus its name, but the colors and sizes differ significantly. The Maypop flower is typically about 2-3 inches in diameter, with pale lavender or white petals and a prominent purple and white corona. A common comparison is with the blue passion flower (*P. caerulea*), which has larger, 4-inch flowers with white petals and a blue, white, and purple corona. The flowers of the edible passion fruit (*P. edulis*) are also distinct, often featuring a rich purple and white coloration and a different filament pattern.
This is perhaps the most significant practical difference for gardeners. The Maypop is renowned for its exceptional cold tolerance. It is winter-hardy down to USDA zone 6 or even 5, as its roots survive freezing temperatures and send up new shoots in spring—a trait from which its common name derives (the "may pop" of new growth). Almost all other passion flower species are tropical or semi-tropical and are severely damaged or killed by frost, often requiring protection or greenhouse cultivation in temperate zones. The fruit of the Maypop is an oval, yellowish-green berry that is edible and tasty, but it is generally smaller and has a different flavor profile than the commercial passion fruit produced by *P. edulis*.
