Steven Foster's Herbalblog

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Intent on reaching the swimming hole on a seething July afternoon, my attention was diverted by a loud pop under foot. Relieved by the realization that the object was vegetable rather than animal, the victim plant caught my attention again, this time by the indescribable, intricate beauty of its bloom. I had stepped on a fruit of the passionflower or maypop. Such is the memory of a New England transplant upon first encountering a maypop in the Ozarks. This fast-growing perennial vine is more widely known as passionflower (Passiflora incarnata). In the Southeast it’s also called apricot vine.

Passionflower’s Name

What design of nature or serendipitous evolutionary event could create a flower of such unusual beauty? Such radiance is beyond scientific rationale. Best to describe it in religious terms. The first Europeans to observe the plant did just that. The name is derived from flos passionis, a translation of fior della passione, a popular Italian name which was applied to the plant to signify religious symbolism. The floral structure was seen to symbolize the implements of the crucifixion—the Passion of Christ— his period of suffering following the Last Supper and the Crucifixion. The three spreading styles atop the stigma were thought to represent the three nails by which Christ was attached to the cross. The five hammer-like anthers atop of the stamens exemplify the hammers used to drive the nails, or to others, Christ’s five wounds. Beneath these floral structures is a fringe of colored filaments, known as the corona. It was believed to depict a halo or perhaps the crown of thorns. Beneath it sits the corolla—with ten petals, each representing the ten apostles at the Crucifixion— save Peter and Judas. Some early missionaries envisioned that the bell-shaped, unopened or recently closed flower held these sacred symbols from the view of heathens who had not yet been converted to Christianity. If that’s not enough, the lobed leaves and long green vines further represent the hands and whips of Christ’s prosecutors. And so, both the common and Latin names—passionflower (Passiflora)—speak of these mysteries. Thomas Johnson editor of the 1633 edition of Gerarde’s Herball described these notions for what they were: “The Spanish Friers for some imaginarie resemblances in the floure, first called it Flos Passionis, The Passion floure, and in a counterfeit figure, by adding what was wanting, they made it as it were an Epitome of our Saviors passion. Thus superstitious persons semper sibi somnia fingunt” [always see contrived images]. The species name of passionflower “incarnata” means “made of flesh or flesh-colored.” Maypop, of course, refers to the fruits, the shape and size of a hen’s egg, which open with a resounding pop when squeezed.

Passionflower Diversity

Depending upon your perspective passionflower is wildflower, weed, ornamental perennial, delectable edible, or medicinal herb. The flowers of one hybrid P. x alatocaerulea (a cultivated hybrid between P. alata and P. caerulea) are used in perfumery. That covers all the bases of the definition of an herb— any plant or plant part used for culinary, fragrant or medicinal purposes. Therefore, it deserves a place in herb gardens. Here we will primarily focus on the common maypop, wild passionflower, or apricot vine (P. incarnata) the only native species that is hardy and can be widely cultivated in much of the U.S.

The passionflower (P. incarnata) is an herbaceous  perennial, trailing or climbing, with tendrils. The white to blue purple flowers are up to three inches across. It occurs in waste ground, along fence rows, roadsides, and fields from Pennsylvania to southern Florida, west to east Texas and north to southern Missouri, and Ohio.  In the United States we have about 25 native or naturalized species of Passiflora, but only the passionflower and its diminutive relative wild yellow passionflower (P. lutea), with tiny yellow flowers about an inch across, are hardy natives. Wild yellow passionflower is rarely grown in gardens.

The genus Passiflora, with only a handful of temperate species, explodes in diversity in the American tropics with about 500 species. An additional 20 species occur in Indomalaysia and the south Pacific islands. Some have edible fruits. Others do not. About 30 species of passionflower have edible fruits. At least 40 species and numerous cultivated varieties are found in American gardens, primarily in warmer areas.

The undisputed edible king of passionflowers is passionfruit or purple granadilla (Passiflora edulis) which is cultivated for its edible fruits and juice. It is native to southern Brazil, Paraguay and northern Argentina. A large passionfruit industry in Brazil grows purple-fruited forms for the fruits, while yellow-fruited cultivated forms are used for juice extraction. Passionfruit is grown commercially in Australia, New Zealand, Hawaii and other tropical regions. It was introduced into Hawaii in the 1880s, where it became a popular home garden flower and fruit on the islands. By the 1930s it had become wild on every island in the archipelago. Commercial cultivation operations are also found in Kenya, South Africa, India, Pacific islands, and other tropical regions where it thrives. According to Arthur O. Tucker passionfruit has proven hardy in protected situations as far north as Ontario. If you do buy seeds or plants of this species and don’t live in a subtropical area, you will probably want to bring it indoors for the winter. The vast majority of scientific references to Passiflora species refer to the passionfruit and its many cultivars and hybrids. Much of the research has focused on attempting to unlock the unusually complex, sweet, delicate-perfume flavor of the fruits.

Other passionflowers are grown as subtropical food plants as well. The tropical American species running pop (P. foetida), now a weed in the old world tropics, is grown for its fruit, as is the banana passionfruit (P. mollissima). Yellow granadilla, or water lemon (P. laurifolia), also known as Jamaica honeysuckle, is a commercial fruit crop. Its name does not derive from any resemblance to honeysuckle (Lonicera species) but from the fact that the fruits are eaten by sucking out the pulp from the rose-scented fruit.  Sweet calabash (P. maliformis) is grown to produce grape-flavored juice. Giant granadilla (P. quadrangularis) sports a large fruit about eight inches long which is eaten as a vegetable. Individual fruits of cultivated varieties of giant granadilla may weigh as much as several pounds. When still green the rind is boiled and eaten as a vegetable. If ripe, it is eaten iced (with sugar) or the fruit-wall may be candied. Members of the genus Passiflora hybridize readily and have produced numerous cultivated hybrids, primarily grown in the tropics for fruit production.

Other passionflowers such as red-flowered species P. vitifolia which sports crimson red flowers, or blue passionflower (P. caerulea) are grown as ornamentals. They do not produce edible fruits.  Some cultivars of the blue passionflower such as ‘Constance Elliot’ which sports white flowers, are reported to be hardy in protected situations as far north as central Delaware. The tender ornamental passionflowers can be grown as annuals, taking cuttings in late summer rooting them before the first frost, or growing them in a large container to winter it over.

Growing Passionflower

Subtropical edible or ornamental passionflowers are primarily relegated to the realm of the specialized collector, or those who have access to a greenhouse. But the passionflower (P. incarnata) can be grown by most herb gardeners. While passionflower is commonly regarded as a southern plant, it will grow as far north as the Boston area, and I suspect, if placed in a well-protected situation and mulched through the winter, it would even survive as a perennial in central Maine. Here in the Arkansas and Missouri Ozarks, the native passionflower withstands temperatures of -25° F. without any protection. When purchasing seeds or plants it’s probably a good idea to at least inquire where the plant material originated, if the seller knows. Passionflower seeds or plants from south Florida are probably likely to survive in New England, than plants originating from more northerly areas. While dying back to the ground each year, it makes a marvelous fast-growing climbing cover for a fence, or can be trained on a trellis as a focal point for the herb garden. In the South it will grow 20—30 ft. in a single season. In more northerly areas, expect a growth of about 15 feet in a season. Passionflower grows in waste places, thriving in relatively poor, sandy, acidic soils. Good drainage is essential. Full sun is necessary.

Propagation is by seeds, cuttings, or layering. Cuttings about six inches in length can be taken from mature plants, then rooted in sand. Maypop grows readily from seed—if one has patience. After harvesting the fruits, clean out the seeds from the mucilaginous fleshy aril surrounding them, then plant immediately. They may germinate late in the summer, or may sit dormant until the following spring. The experience of many who try passionflower from seed for the first time is disappointment, born of expectations that the seeds will germinate in a couple of weeks. Wait a year if you have to. The result of your patience and suspense will be worth it a few years later.

Propagation by layering can be achieved simply by removing the leaves from a small section of a stem in late summer, placing a portion beneath the soil, with a leafy end sticking out of the ground. Water well, and in a few weeks, the buried stem should produce roots. But wait. Keep the layer in the ground through the dormant months, allowing it to develop a full root system before transplanting. The layered cutting can be severed from the mother plant and placed in a new location. With a little luck and persistence, you will soon have your own passionflower planting. Of course, the easiest technique is simply to buy plants from a nursery. Young plants are often slow-growing, taking two or three years to establish. After that, watch out—it can entangle everything else in your perennial beds.

Passionflower as Food

In his “Thousand Mile Walk to the Gulf” John Muir speaks of the apricot vine (maypop) has having a superb flower “and the most delicious fruit I have ever eaten.” If you grow passionflower, you must taste the fruits. The fruits of the passionflower ripen from yellowish to light brown in color. The slimy aril covering the seeds is very sweet and fruity when ripe. The hard seeds can be separated from the pulp through a sieve or apple sauce strainer. Or if you are in the garden, you can pop open the ripe fruit and suck the delicious pulp from the fruit. Make sure that the fruit is not over-ripe. Perfectly ripe fruits are delicious . Over-ripe fruits ferment into a foul paste.

At the annual funding-raising auction of the Arkansas Native Plant Society a few years ago, I was the fortunate high bidder on two jars of maypop jelly. I know of no other native fruit whose flavor is best described as “indescribable.” The best maypop jam recipe can be found in Billy Joe Tatum’s Wildfoods Field Guide and Cookbook (Workman Publishing Co., Inc., New York 1976). Billy Joe’s book, which transformed wild edible from the realm of survival food to haute cuisine, also contains a delicious recipe for maypop punch, and maypop ice, a cool refreshing beverage with juiced maypops and pineapple sherbet. To make 10 half-pint jars of maypop jam, she combines 5 cups of gently rinsed maypops, with a 1/2 cup of lemon juice, one box of powdered pectin and 7 1/2 cups of sugar. Enough water is added to barely cover the fruit. Standard procedures for making jam are followed.

Passionflower was a minor food item of American Indian groups in the Southeastern U.S. Archaeological evidence shows that maypop seeds could be found at Indian camp sites over 5000 years old. Seventeenth century visitors to Virginia such as the Englishman William Starchey observed the harvesting of fruits from  corn fields. Calling it maracock, Starchey described it as “of the bigness of a green apple, and hath manie azurine or blew kernells, like as a pomegranat, a good sommer cooling fruit.” It is unclear whether native groups intentionally planted the passionflower as a crop or whether it simply occurred naturally on the disturbed ground at the edge of the plot.  It is clear, however, that native groups of the Southeast enjoyed this late summer fruit for many centuries.

Passionflower as Medicine

Passionflower never became an important medicinal plant in the U.S. Like many American medicinal plants, however, it is more highly revered in modern Europe than in its native land.  In the second volume of his 1830 Medical Flora or Manual of Medical Botany of the United States the naturalist Constantine Samuel Rafinesque makes one of the earliest reference to medicinal use. He recommends a syrup of the fruits as a cooling agent for fevers. The leaves, he says are used externally, and the juice given to dogs to cure the “staggers or epilepsy.” This use was first recorded in 1787 by a German surgeon, Johann David Schoepf, who served with Hessian mercenaries siding with the British during the Revolutionary War.

In Europe, passionflower products are used as mild nerve sedatives and a sleep aid. The introduction of this medicinal use is credited to  Dr. L. Phares of Mississippi who in an 1840 issue of the New Orleans Medical Journal, recorded its use. Remaining an obscure reference in the literature, Dr. I.J.M. Goss of Atlanta reintroduced passionflower into Eclectic medical practice in the late nineteenth century.

Dr. E. D. Stapleton writing in a 1904 issue of the Detroit Medical Journal summed up his experience in using passionflower tincture to treat insomnia “I would say that its action is best obtained in cases of nervousness due to causes other than pain-that it is slow in acting because it is not a narcotic, but a nervine and sedative. It relieves irritation of the nerve-centers and improves sympathetic innervation, thus improving circulation and nutrition, and is as a rule sure in its results-no bad after-effects, no habits formed”.

In the eighteenth edition of King’s American Dispensatory (1898), authors H.W. Felter and J.U. Lloyd characterize its action. “Its force is exerted chiefly upon the nervous system, the remedy finding a wide application in spasmodic disorders and as a rest-producing agent. . . It is specially useful to allay restlessness and overcome wakefulness, when these are the result of exhaustion, or the nervous excitement of debility. It proves specially useful in the insomnia of infants and old people. It gives sleep to those who are laboring under the effects of mental worry of from mental overwork.”  Sounds like I need some myself.

It is interesting to note that while yellow wild passionflower (P. lutea) is very rarely mentioned in the medicinal plant literature, Dr. Phares of Mississippi is said to have used this small North American vine interchangeably with the common passionflower. I have made a tincture (alcohol extract) of both plants. They have a very similar flavor and fragrance. The fruits are decidedly different, though. Those of P. lutea are globular black berries, about 1/4 inch across. They have a much more acidic flavor than maypop.

Herbal Medicine Past and Present by John K Crellin and Jane Philpott (Duke University Press 1990) is based on extensive interviews over a seven year period with an Alabama herbalist, Tommie Bass. Bass, quoted in the text says, “Its the most wonderful sleep and pacifying plant, valuable for a nerve medicine . . . Any good sleeping medicine has passion-flower in it.”

Today the American passionflower is used in a number of proprietary phytomedicines (plant medicines) in Europe, used for “conditions of nervous anxiety.” A dosage of  4-8 g. of the herb per day in infusion (tea) or other methods of preparation such as equivalent extracts for internal use. Products are made from the fresh or dried whole plant (excluding the root). It is usually collected at flowering time. It is also widely used as a sleep aid. The fresh or dried whole plant as well as their preparations are also used in daily dosages equivalent to 0.5 to 2 g. of the herb, or 2.5 g in tea (about a teaspoon of the dried, ground herb). Preparations include tea, tinctures, fluid extracts, solid extracts, and even sedative chewing gums. Passionflower is also combined with valerian and hawthorn in products used in Europe to treat digestive spasms, gastritis, and colitis.

Like many medicinal herbs, the exact chemical components responsible for the plant’s sedative activity have not been definitively identified. Researchers have found small amounts of components known as harmala-type alkaloids in the plant, as well as compounds called flavonoids. In Germany, passionflower preparations were regulated to  contain no more than 0.01 percent of harman alkaloids. Some believe the flavonoids to be active compounds. Still other researchers believe that substances known as maltol and ethyl-maltol may be responsible for the sleep-inducing and muscle relaxant activity attributed to passionflower. Generally it is believed that the sedative effect is probably a result of an interaction between the alkaloids and flavonoids found in the extract.

While the active constituents and mechanism of action of passionflower requires more studies, various studies confirm a sedative effect on the central nervous systems. The degrees of effect is dependent upon dose. Extracts of the herb inhibit fungi and bacteria. Studies indicate that the herb (or its extracts) relieves spasms, has a sedative effect, allays anxiety, and lowers blood pressure. The experience of numerous medical practitioners and herbalists in Western herbal traditions generally confirm the plant’s safety and efficacy.

Most of the supply of dried passionflower leaves either cultivated or wild-harvested in the U.S. goes to the European market. Farmers treat it as a weed in the South. USDA scientists focus on developing it as a new fruit crop for the U.S. Gardening enthusiasts appreciate the passionflower and subtropical passionflowers for their fantastic, colorful floral assemblage. Wild food enthusiasts, delight in its delicate, delectable flavor. And if you are a herb gardener, you’ll undoubtedly enjoy adding passionflowers to your herbary.

References:

ESCOP. 1997. Passiflora herba. In ESCOP Monographs on the Medicinal Use of Plant Drugs. vol. 4. Exeter, UK: ESCOP Secretariat.

Felter, H. W. and J. U. Lloyd. 1898 Kings American Dispensatory, 18th ed. 2 vols. Portland, OR: Eclectic Medical Publications, reprinted 1983.

Foster, S.1991. “The Passionflowers.” The Herb Companion (August/September): 18-23.

Foster S. 1993. Herbal Renaissance: Growing, Using and Understanding Herbs in the Modern World. Salt Lake City, UT: Gibbs Smith.

Foster, S. and J. A. Duke. 2014. Peterson Field Guide To Medicinal Plants: Eastern and Central North America. Boston: Houghton Mifflin Harcourt Co.

Gremillion, K. J. 1989. The Development of a Mutualistic Relationship Between Humans and Maypops (Passiflora incarnata L.) in the Southeastern United States. Journal of Ethnobiology. 9(2):135-158.

Hoch, J. H. 1934. The Legend and History of Passiflora. American Journal of Pharmacy. (May): 166-170.

Krellin, J.K. and J. P{hilpott. 1990. Herbal Medicine Passt and Present. 2 vols. Durham, NC: Duke University Press.

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McGuire, C.M. 1999. Passiflora incarnata (Passifloraceae): A New Fruit Crop. Economic Botany 53(2):161-176.

Olin, B. R., ed. 1989. “Passion Flower.” The Lawrence Review of Natural Products. (May):1-2.

Speroni, E., and A. Minghetti.1998 Neuropharmacological Activity of Extracts from Passiflora incarnata. Planta Medica 54: 488-491.

Ulmer T, MacDougal JM. 2004. Passiflora: Passionflowers of the World. Portland, Oregon: Timber Press.

Vanderplank J. 1991. Passion Flowers (and Passion Fruit). Cambridge, MA: The MIT Press.

Weiss, R.F. 1988. Herbal Medicine (translated from German by A.R. Meuss). Beaconsfield, England: Beaconsfield Publishers Ltd.