Passiflora incarnata, commonly known as maypop, purple passionflower, true passionflower, wild apricot, and wild passion vine, is a fast-growing perennial vine with climbing or trailing stems. A member of the passionflower genus Passiflora, the maypop has large, intricate flowers with prominent styles and stamens. One of the hardiest species of passionflower, it is both found as a wildflower in the southern United States and in cultivation for its fruit and striking bluish purple blooms.
The stems can be smooth or pubescent; they are long and trailing, possessing many tendrils. Leaves are alternate and palmately 3-lobed and occasionally 5-lobed, measuring 6–15 centimetres (2.4–5.9 in). They have two characteristic glands at the base of the blade on the petiole. Flowers have five bluish-white petals. They exhibit a white and purple corona, a structure of fine appendages between the petals and stamens. The large flower is typically arranged in a ring above the petals and sepals. They are pollinated by insects such as bumblebees and carpenter bees, and are self-sterile. The flower normally begins to bloom in July.
The fleshy fruit, also referred to as a maypop, is an oval yellowish berry about the size of a hen egg; it is green at first, but then becomes yellow as it matures. As with other passifloras, it is the larval food of a number of lepidoptera species, including the zebra longwing, the Gulf fritillary, the crimson-patched longwing, the Julia, the Plebeian sphinx, and the variegated fritillary. In many cases its fruit is very popular with wildlife. The egg-shaped green fruits 'may pop' when stepped on. This phenomenon gives the P. incarnata its common name, as well as the fact that its roots can remain dormant for most of the winter underground and then the rest of the plant "pops" out of the ground by May, unharmed by the snow.
The maypop occurs in thickets, disturbed areas, near riverbanks, and near unmowed pastures, roadsides, and railroads. It thrives in areas with plentiful sunlight. It is not found in shady areas beneath a forest canopy.
The Cherokee in the Tennessee area called it ocoee; the Ocoee River and valley are named after this plant, which is the Tennessee state wildflower. For thousands of years the maypop was a staple food and medicinal plant for the Cherokee and to this day it is a revered piece of their heritage. This, and other passionflowers are the exclusive larval host plants for the Gulf fritillary and non-exclusive for the variegated fritillary butterflies.
Passiflora incarnata is easily cultivated and in its native range and homeland is a common low maintenance garden plant that can be trained to adorn fences and arbors. The wild maypop is an aggressive vine native to the southeastern United States extending into the central US reaching Illinois, Indiana, and Ohio. The vines can carpet the floor of thickets within days in favorable weather. The plants grow in full sun and need direct sunlight for at least half of the day. The best soils for P. incarnata are well-drained  but the plants tolerate occasionally wet and acidic soils. The plants have a high drought tolerance. P. incarnata can be planted all the year in zone 7–11 (hardiness zone). The space between two plants is 36–60 inches (91.44 – 152.4 cm). One to two years are necessary before they begin bearing. Each flower has a very short life (about one day). Then the fruit develops in two to three months. The harvest depends on vine size and age of the plant but one reported 10–20 fruits per vine. Seeds can be collected in the fall after the fruit has begun to shrivel. There are some problems with nematodes and caterpillars in the culture of P. incarnata.
The flowers appear suitable for bumblebee pollination and may attract ruby-throated hummingbirds. As both bees and hummingbirds look for nectar, the pollen filled flower anthers brush the back of the bee or the face of the hummingbird, enabling pollen to be readily transferred to the central sticky stigma.
Passiflora incarnata can potentially become an agricultural weed. The genus Passiflora introduced for agricultural purpose has been reported as an important weed in certain regions of the world. The United States Department of Agriculture notes that P. incarnata is referred to as a weed by these publications: Weeds of Kentucky and adjacent states: a field guide and Weeds of the United States and Canada.
Historical uses and folk medicine
Historically, the plant has been used as a herbal medicine in the belief it may treat anxiety, insomnia, or hypertension, but the clinical research on possible effects of the plant have been of poor quality, with no certainty about whether it is safe or effective. Passionflower is included in pharmacopeias, such as the European and British Pharmacopoeias in which the dried aerial parts of the plant are mentioned. In North America and South America, tea made from the roots is used as a tonic.
In traditional medicine, passionflower is reputed to have sedative effects as used historically in Europe, but in 1978, the U.S. Food and Drug Administration (FDA) prohibited its use in over-the-counter sedative preparations because it had not been proven safe and effective. When used in food manufacturing as a flavor, passionflower is generally recognized as a safe substance (GRAS).
P. incarnata may increase main effects or side effects of medications listed above.
For oral consumption, pregnant or breastfeeding women should use caution and seek medical advice before orally consuming P. incarnata. The effects of oral ingestion of the plant compounds on reproduction or on unborn child have not been tested. The oral consumption of this plant may prejudice the ability to drive and use machinery.
P. incarnata contains flavonoids and alkaloids, with leaves containing the greatest concentration of flavonoids. Other flavonoids present in P. incarnata include chrysin, apigenin, luteolin, quercetin, kaempferol, and isovitexin.
The fruit of passionflower may be used for jams, jellies and desserts. The juice is a favourite flavouring in drinks. It can be used as a fresh substitute for its commercially grown South American relative, Passiflora edulis, a related species with similar sized fruit. The fruit can be eaten by hand, as indicated by its common name, given to it by Cajuns: liane de grenade or "pomegranate vine". It has a slightly sweet-tart taste and a pleasant scent when fully ripe.
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