A passion flower is any plant in the Passiflora genus, a group of roughly 550 species native to the Americas, with some found in Australia and Southeast Asia. Most are climbing vines that produce some of the most visually striking flowers in the plant world. Beyond their beauty, certain species have a long history of medicinal use for anxiety and sleep, while others produce the tropical fruit you’ll find in grocery stores and cocktail menus.
Why It’s Called a Passion Flower
The name has nothing to do with romance. When Spanish missionaries arrived in the Americas in the 1500s and 1600s, they saw the flower’s complex anatomy as a living illustration of the Passion of Christ, the story of his crucifixion. They mapped Christian symbols onto nearly every part of the bloom: the ring of hair-like filaments represented the crown of thorns, the three stigma at the center stood for the three nails, the five pollen-bearing anthers symbolized the five wounds, and the spiraling tendrils of the vine were read as the lashes of the scourging. Even the round fruit was said to represent the world Christ came to save.
This symbolism gave missionaries a visual teaching tool in an era before printed catechisms. Once the plant reached Europe, it picked up religious names in other languages too: “Jesus’ Passion” and “Crown of Thorns” in German, “Our Lord’s Flower” in several traditions. The name stuck, and today “passion flower” refers to the entire genus regardless of any religious association.
What a Passion Flower Looks Like
Passion flowers are immediately recognizable and unlike almost anything else in a garden. The most commonly grown species, Passiflora incarnata (purple passionflower), produces pale lavender blooms with five petals and five sepals that form a flat, star-shaped base. Rising from the center is the corona, a dramatic fringe of dozens of thread-like filaments, typically white or lavender with purple bands. Above this fringe, the reproductive structures sit on a raised central column, with the stamens and pistils arranged in a way that looks almost engineered.
The plants are vigorous climbing vines that use tendrils to grip fences, trellises, and other structures. Leaves vary by species but are often deeply lobed with three or five fingers. Many species produce egg-shaped fruit that turns from green to yellow or purple when ripe.
Edible vs. Medicinal Species
Two species dominate human use, and they serve very different purposes. Passiflora edulis is the one grown commercially for its fruit. Passion fruit has a tart, intensely aromatic pulp filled with crunchy seeds, and it’s widely used in juices, desserts, and sauces. This species has little notable effect on the nervous system.
Passiflora incarnata is the medicinal species, used for centuries as a calming herb. It’s the one sold in supplement aisles as “passionflower” in capsules, tinctures, and tea blends. It does produce edible fruit (sometimes called maypop), but it’s primarily valued for its effects on anxiety and sleep. When you see “passion flower” on a supplement label, it almost always refers to this species.
How It Calms the Nervous System
Passionflower’s calming effects trace back to GABA, a brain chemical that slows nerve activity and promotes relaxation. Of 21 plants tested in one study, passionflower extracts contained the highest levels of GABA. That GABA isn’t just sitting passively in the plant. When researchers applied passionflower extract directly to brain cells, it activated the same receptors that anti-anxiety medications target. Blocking those receptors eliminated the calming effect entirely, confirming GABA was doing the work.
Passionflower also contains plant compounds called flavonoids that bind to these same receptors at a different site, potentially boosting the calming signal. Researchers have proposed that passionflower works through a combination: the GABA it contains directly activates calming receptors, while other compounds in the plant help GABA cross into the brain more effectively and amplify its effects once there.
What Clinical Studies Show
Passionflower has been tested head-to-head against pharmaceutical anti-anxiety drugs with surprisingly competitive results. In one study of patients given passionflower before a medical procedure, 68% reported feeling calm, compared to only 33% of those given a standard sedative. Just 4% of the passionflower group experienced serious anxiety, versus 20% in the sedative group. The passionflower group also had fewer side effects: half reported drowsiness, compared to over 80% in the drug group.
Another trial compared passionflower extract to a benzodiazepine for generalized anxiety disorder over four weeks. Both reduced anxiety by similar amounts, but the passionflower group experienced less impairment in their ability to work and function during the day. A separate study looking at preoperative anxiety found passionflower “definitely more effective” than the same class of medication for calming patients before surgery.
These are relatively small studies, and passionflower is not a replacement for prescribed medications for serious anxiety disorders. But the pattern across trials is consistent: passionflower produces meaningful anxiety relief with fewer side effects than conventional sedatives.
How People Use It
Passionflower is available as dried herb for tea, liquid extracts, tinctures, and capsules. For tea, a typical serving uses a quarter to two grams of dried herb steeped in hot water, taken two to three times daily or 30 minutes before bed. Liquid extracts and tinctures are taken by the dropperful, usually two to three times a day. Capsule doses in clinical studies have ranged up to about 90 mg of concentrated extract daily for anxiety, though products vary widely in concentration.
Most people use passionflower for one of three purposes: reducing everyday anxiety, improving sleep quality, or calming nerves before a stressful event like a dental visit or flight. It’s one of the most common herbal ingredients in “calming” tea blends, often paired with chamomile, lemon balm, or valerian.
Safety and Who Should Avoid It
Passionflower is generally well tolerated, but it does carry real risks for certain groups. It should not be used during pregnancy because it can stimulate uterine contractions. Animal studies have also shown disrupted development in offspring exposed to passionflower, reinforcing the warning. There is not enough safety data to recommend it while breastfeeding.
If you have surgery scheduled, stop taking passionflower at least two weeks beforehand. It can interact with anesthesia drugs, potentially slowing the nervous system too much when combined. For the same reason, combining passionflower with prescription sedatives, sleep medications, or anti-anxiety drugs can amplify drowsiness and impair coordination beyond what either would cause alone.
Growing Passion Flowers
Passion flowers thrive in warm climates and grow quickly once established. Passiflora incarnata is hardy enough to survive winters in USDA zones 6 through 10, dying back to the roots in colder areas and re-emerging in spring. It needs full sun, well-drained soil, and something to climb. A single vine can spread aggressively through underground runners, so many gardeners grow it in containers or with root barriers.
Tropical species like Passiflora edulis and the showier ornamental varieties need frost-free conditions or greenhouse protection in cooler climates. Most passion flowers bloom from midsummer through fall, with individual flowers lasting only a day or two but appearing in succession over weeks. Pollination often requires a second, genetically different plant, and some species depend on specific pollinators like carpenter bees or certain butterflies to set fruit.