By: Scott Perry
In Brazil, it’s called "Maracuja;" in Jamaica, it’s "Granadilla;" in Hawaii, it’s "Lilikoi," and throughout Texas, it’s "May-pops." Regardless of its name, though, the plant we now know as the passionflower is universally looked upon with awe and fascination. This vigorous flowering, sometimes fruiting vine looks at first like something alien. But it is a Texas native, and is becoming more available throughout the state. Having held significant religious and medicinal value, and prized for its unique beauty, few plants have evoked the same wonder and curiosity that the passion vine has.
Native to South America, Central America, and North America, the passion vine can be found growing in Texas, Kentucky, North Carolina, Illinois, Hawaii, and as far north as New York. According to legend, a Jesuit priest in Peru found the vine in 1620. That night, in a vision, the priest associated components of the blossom with Christ’s Passion, leading to the common name, "Passionflower":
The five petals and five sepals were representative of the ten faithful apostles present at the crucifixion; the five anthers represented Christ’s wounds; the three pistils, the nails. The corona was the thorny crown, while the leaves were reminiscent of the Roman spear, and the tendrils were their whips.
First documented in the Amazon by Spanish physician Nicolas Monardes in the 1560s, the leaves of the passionflower had long been used as a natural sedative by indigenous peoples, while the fruit was a favorite staple. When Monardes brought the vine back to the Old World, it quickly became popular as the source of an herbal tea. It has since been used as a remedy for nervousness, insomnia, and a myriad of other ailments, and has been recorded in North American medicine for over two hundred years. Today, the passionflower is widely used in herbal medicine to aid treatment of sleep disorders, nervousness, and headache. Its favor as a sedative and analgesic is largely due to its effectiveness without any disorientation or narcotic after-effects. The subject of a great deal of research for nearly a century, many medicinally-active components have been identified in all parts of the plant. However, none of the active compounds has been identified as producing the specific effects that all generate in combination; the mechanism by which its curative properties work has yet to be fully understood.
There are over 500 species of passionflower, with new hybrids being introduced constantly. Many of these are becoming increasingly available through specialty and native plant distributors, and even through local garden centers.
Because passion vines are largely tropical plants, they can withstand the extreme heat common to south Texas and the Gulf Coast. In southern parts of Texas, the passion vine can be kept outdoors year-round, where it inevitably becomes your garden’s focal point. However, they do appreciate somewhat cooler (55-65°F) temperatures.
There are several varieties available commercially which can withstand some cold and frost without damage. Texas-native Passiflora incarnata (the "May-pops") can withstand temperatures as low as 18°F, while the widely-available Hardy Blue passionflower, P. caerulea, can tolerate temperatures to 25°F. In areas with winters too severe for passionflower to survive outside year-round, the plant can be kept potted indoors during the winter months in a bright, cool spot, receiving at least four hours of sun per day. Most species of passionflowers thrive in full sun; however, in parts of the state where the afternoon sun can be brutal, some degree of shade is welcome. Planting near an overhang (whether a tree, an eave, or a fence) not only offers some shade during the hottest parts of summer, but can also provide some frost protection during winter.
Regular watering is necessary to maintain vigorous growth. This is especially true of the fruiting varieties, which require additional moisture as fruits are maturing. If fruit begins to shrivel or to drop prematurely, the vine has likely been under-watered. Given favorable conditions and ample moisture, passionflowers can be flowering and fruiting almost continuously throughout the growing season.
The most important requirement common to all passion vines is good drainage. The passionflower responds well to regular watering and it can tolerate periods of drought. However, if it is allowed to stand in constantly wet soil, the plant will suffer and quickly fail.
While tolerant of many soil types, passion vines require regular fertilization to maintain their strong growth. A 10-5-20 fertilizer should be applied several times each year, beginning in early spring before new growth appears. This is especially important for frost-damaged plants. Light feeding should continue at four- to six-week intervals throughout the growing season. Avoid overfeeding, as this can cause root damage and death of the vine. Fertilizers too high in nitrogen can cause excessive foliage development; consequently, flower development can suffer.
Passionflower is a vigorous performer, given ample moisture, good drainage, and a sunny exposure. This vine will rapidly and eagerly attach itself (via its twining tendrils) to any open structure or plant upon which it can find support. Trellises need not be elaborate; they will quickly become buried beneath mounds of foliage. Depending upon variety, passion vines can grow to thirty feet or more in a single season. Since it is such an enthusiastic grower, it requires some occasional pruning to keep it in bounds. Pruning is best done during winter months, when the plant is not actively growing. All dead and weak growth should be trimmed back to healthy stems with several buds each to promote vigorous growth in the spring; strong stems should be cut back by at least one third. As passionflower is susceptible to some viral diseases, shears should be thoroughly disinfected before and after pruning. If the vine is to be over-wintered outdoors in areas where the cold may cause it to die back to its roots, it can be trimmed to 8" to 12" from the soil. Apply a thick layer of mulch or straw to protect its shallow roots against any frosts.
Passion vines are robust, relatively pest-free plants with surprisingly few garden insects causing any real harm. The biggest insect threat to your passion vines comes from several Texas butterflies of the family Heliconius, for which passionflower is the sole larval host. Among these butterflies are the Zebra, the Julia, and the Gulf Fritillary. Some compounds found in the passion vine are toxic; ingesting them makes the larvae and butterflies toxic to predators. Unfortunately, Heliconius larvae are voracious eaters, and can defoliate a passion vine quickly. While the caterpillars are easily eradicated with commercial pesticides, try selectively reducing their numbers by physically relocating them first. This way, you are still likely to see some extra butterflies later in the season, and you will not impact any beneficial species. In fact, some gardeners grow passion vine primarily to attract butterflies to their gardens.
Fruit-bearing varieties require pollination before setting fruit. Some varieties (such as P. incarnata) are self-pollinating, and require only regular visits from insect pollinators. Other varieties (such as P. edulis) are self-sterile, and require pollen from genetically compatible plants in order to fruit. Large-bodied bee species like the carpenter bee make the best natural pollinators, though honey and mason bees can be effective on some smaller-flowered varieties. The most reliable pollinator for backyard fruit production, however, is you: hand pollinating is usually the best way to ensure fruit production.
If your curiosity has been piqued and you are ready to add passionflower to your landscape, you might want to start with one of the following varieties, noted for their beauty, their availability, and their ease of culture:
Passiflora incarnata-the Texas-native "May-pops." It produces small, edible fruits which, when inadvertently stepped on, produce a loud "pop", giving the species its common name. This is one of the most hardy passion vines available, is self-pollinating, and grows reliably from seed.
Passiflora alatocaerulea-This hybrid has become one of the most widely-available cultivars. Grown commercially for use in perfume manufacture, it has large, fragrant, 3-4" flowers that bloom throughout the growing season. Hardy to about 40°F, it requires some frost protection or relocation during the winter months.
Passiflora vitifolia-This passionflower produces scarlet red flowers with yellow to white filaments, and edible fruit. Becoming more easily found at garden centers and nurseries, P. vitifolia is hardy to about 28°F, and can be grown outdoors year-round in southern parts of the state.
Need advice about your passion vines? Passiflora Society International is a good starting place. You can find contact information on the internet at http://www.esb.utexas.edu/philjs/PSI/psi.html. Also, the Passiflora Enthusiast Discussion List delivers discussions from passionflower devotees worldwide directly to your inbox; send an email to BIHOREL@cris.com with the word PASSIF in the subject line, and "SUBSCRIBE your name" in the message portion of the letter.
Wherever you are, there is a variety of passionflower perfect for your garden. Your minimal work will be rewarded with months of lush growth and beautiful blossoms, and if you are lucky, some of the most delicious fruit you will ever taste!