Passiflora incarnata Seeds | American Passion Flower
LATIN NAME: Passiflora incarnata
COMMON NAME: American Passion Flower, Maypop
Plant Profile
Look at the leaf stalk and the stipules of a growing shoot and you will find small dark glands, usually in a pair on the petiole. These are extrafloral nectaries, and they secrete a sugary reward that has nothing to do with pollination. Ants come for the nectar and stay to patrol the plant, driving off the caterpillars that would otherwise strip the leaves. The arrangement is a hired guard service, and it is one of the best documented examples of it in a temperate vine.
The flower is built on a plan that has no equal in the garden. Five sepals, each with a small awn at the tip, and five white petals sit beneath a corona of purple-fringed filaments. From the centre rises a stalk, the androgynophore, carrying five stamens, and above them a single ovary topped by three styles whose club-shaped stigmas are bent over to form a shape like a hammer. Seventeenth-century missionaries read the whole assembly as the instruments of the crucifixion, and the name stuck.
In its native range the vine is a roadside plant, scrambling over fences and up hedgerows, and it is the larval host of the Gulf fritillary and the variegated fritillary, whose orange and silver-spangled caterpillars will strip a young shoot in a couple of nights. A specialist solitary bee, Anthemurgus passiflorae, collects pollen from no other plant. If you want fruit and flowers, grow a second plant or accept the holes in the foliage; a vine that is not being eaten is usually a vine that is not being used.
Science & Biotechnology
The aerial parts carry a set of flavonoids, among them chrysin, vitexin, isovitexin, orientin and homoorientin, together with maltol, and the plant was the subject of a European traditional-use monograph for mild nervous tension and for sleep. Traces of beta-carboline alkaloids have been reported in some samples, though levels vary and are low. The sedative reputation is old in North America as well: the Cherokee used the root, and nineteenth-century herbalists carried the plant into the domestic materia medica.
Uses & Benefits
The fruit is a large oval berry, green and heavy through summer and pale yellow when ripe, with a rind thick enough to hold its shape after the pulp has gone. Inside, the seeds sit in a juicy, aromatic aril that tastes tart and tropical; older American texts call the plant wild apricot for the smell of the ripening fruit. By the time the shell is dry it is mostly air, which is what makes it pop. Collect the fruit after it drops rather than pulling it, and the flavour is at its best.
Walk through the tea aisle of any health shop and you will find the dried herb blended with lemon balm, valerian and chamomile, almost always as the aerial parts rather than the root. The flavour is soft and hay-like with a faint bitterness, and it takes well to a little honey. Use only top growth that you have dried quickly in the shade, since the active flavones sit in the leaf and the young stem, and a slow damp dry turns the material brown and dull.
Growing from Seed
Sow the seed in a deep pot of loam, compost and sharp sand, covering it lightly, and keep the pot cool and moist through a winter before expecting anything, because the seed is slow to break dormancy. In the ground, plant out a young vine at the foot of a trellis or a fence with its crown just at soil level, water it well through its first summer, and give it a sunny spot with something to climb.
This is an herbaceous perennial, not a woody climber, and it spreads underground as well as upward. In autumn the stems die back completely, and in spring new growth rises from the crown as well as from suckers sent up well away from the original plant, so a single vine can become a patch in a few seasons. That suits a rough corner, a fence line or a bank where you want cover, and it is a nuisance in a tight border; give it at least a metre of clearance from anything delicate. Tie in the new shoots as they extend, because the tendrils will grip a wire readily but a stem left unsupported will simply sprawl across the bed, and cut the dead stems to the ground in spring once new buds are showing.
Our Take
Maypop is worth growing for the flowers alone, which open in the morning and last a single day, so the pleasure is in checking the vine daily through midsummer. Give it sun, drainage and something to climb, and let the caterpillars have their share. For the same structure in a frost-free garden, Passiflora coccinea adds scarlet, the banana passionfruit brings a longer, softer flower, and anyone who wants fruit rather than flowers should grow Passiflora edulis under cover.
Related Reading
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