Can I grow Passion Flower as an annual in my zone? If so, how quickly will it grow and how should I treat it when it gets too cold? I plan to start from seed indoors.
I think that most passies need more than a season to reach blooming size from seed and being in zone 4 your season is extremely short. They are easy enough to winter over indoors under grow lights. I doubt that even the hardiest variety would be able to survive your winter in the ground.
I was so hoping to sow indoors and then move it outside and enjoy it as an annual.
You can start the seeds inside and take the plant out during the summer but it needs to come inside over the winter. If you start a passie now, depending on the variety you might have flowers next summer. Some passiflora seeds take a very long time to germinate, up to a year. Do you know what variety you want to grow? You might be better off either finding someone who has a cutting or buying a plant from a nursery. Zone 9 Tropicals sells beautiful blooming size plants for very reasonable prices. There are a number of other reliable nurseries but I haven't found one that has plants the size of Zone 9's.
Here is a link that might be useful: Zone 9
Passies are very easy to overwinter also and then your new seedlings will be ready to bloom. Plant your seeds in a pot with a trellis and let them get as big as they can this year, then just bring them into a cool room and cut everything down and water sparingly once a month thru the winter, then around March start bringing it out and watering it more and when you start seeing new growth start to fertilize., I have done this for the past 3 years with one plant and the leaves and blooms get bigger every year.
Incarnata can flower in its first year from seed, and starting indoors early would certainly help boost the odds. But most take two or more years before they mature enough to flower. You could plant an Incense in early spring, and in the fall dig up some of the inevitable root suckers and pot them up for overwintering, planting them again in the spring.
There *is* one species of passiflora that is a true annual, but I don't have my books with me and can't remember what it's called. IIRC, the flowers aren't particularly showy, however.