There are some seed grown passies that never bloom but without trying to keep it outside I wouldn't give up yet. Plants are more prone to spider mites when kept indoors. I get them on indoor and greenhouse plants but never on plants that are outside. I can also get rid of them by putting an infested plant outside and spraying it with a hose regularly. FWIW I've grown many passies, lots of different varieties, from seed and have yet to find one that doesn't eventually bloom for me.

Growing from seed 10 years ago, unless you purchased it from an exotic source, it is most likely either Passiflora edulis or Passiflora caerulea. I would wager it is the latter. In either case your problem is almost certainly not enough light. Most Passiflora prefer a good amount of sun.

I have two possible suggestions for you. Since you are almost ready to give up on it, try putting it outdoors in full sun for the Spring and Summer. P. caerulea tends to bloom in late Spring and early Summer, so as long as you bring it out early enough, it should bloom for you with enough sun. I live in California (zone 9), and ours are in full day harsh sun. We get about a dozen days per year over 100 degrees, and they thrive. Obviously, you will need to be very aware of the watering, since you are used to growing it indoors.

Alternately, make a cutting or two and create new plants to experiment on. If you started them now, it is still possible, though unlikely, that it could bloom this year.

If I am right, and it is Passiflora caerulea, it can withstand quite cold temperatures, even some frost. I would put them into sun as early as it is safe to not get too many days of freeze, as your plants are not used it. As for the spider mites, Karyn is right that they are much more prevalent indoors than out, but even if you did get them, P. caerulea is a strong hardy plant that unless badly infested, can and will survive with a little care. Pests are just part of growing plants, and something we all learn to live with.

One last suggestion. Post or email me pictures of your plant, so I can try to help you identify it. If I am wrong with my P. caerulea guess, or even if it is P. edulis, much of my advice will not be voided.

Good luck and happy growing! Feel free to email me or post with any other questions you may have.

Eric Wortman