With their bright purple-and-white blooms growing on masses of green vines, passion flowers are impossible to miss. Although they are native to the tropics, passion flowers are easy to grow in all but the coldest climates. However, starting them from seed can be a bit of a challenge. To increase your chance of success, always start with fresh seed. Be patient, because germination can be a slow process.
Use fine sandpaper to lightly sand your passion flower seeds, which look somewhat like shriveled almonds. Put the seeds in a bowl of room temperature water and let them soak for 24 hours. Discard any floaters, because they won't germinate.
Fill a planting tray with potting soil. Plant the passion flower seeds, covering them with about 1/4 inch of potting soil.
Mist the soil gently but thoroughly, then cover the tray with clear plastic wrap. The plastic will conserve moisture. Check the tray daily, and if the soil appears dry, mist it lightly.
Put the tray in a room where the temperature is about 85 degrees for eight hours each day, and then move it to a cooler room where the temperature is about 68 degrees for the rest of the day. If you can't move the tray from room to room, place it in a room that stays at 80 degrees, or set the tray on a plant heating mat. If you've used fresh seeds, they should germinate in a month or less. Older seeds can take up to 10 months.
Remove the plastic wrap as soon as the seeds sprout. Leaving it on longer may cause the seedlings to mold.
Choose a planting area that gets partial or full sun, and where the soil drains well. If you notice standing puddles after it rains, select a different spot. The passion flower seedlings should be planted outdoors in mid-spring, after all danger of frost.
Work the soil with a shovel or a pitchfork, and remove any weeds. Add 2 to 3 inches of compost or well-rotted manure to the top of the soil.
Plant the passion flower seedlings, and water them well.The soil should be kept moist at all times, but don't drench it. As the plants grow, provide a trellis or a support that they can grow around.