Passiflora caerulea – The Blue Passion Flower is the most common species available and is a fast growing semi-evergreen vine, reaching heights of 10 to 15′ here. In hard winters it may suffer dieback, but it readily regrows from its extensive root system. It often produces an edible (tastes like blackberry when cooked) yellowish-orange egg-shaped fruit. Zone 7 hardy.
Passiflora quadrangularis – The Giant Granadilla is well deserving of its common name as it produces huge flowers and 8-12″ long edible fruit (in the tropics). The growth is also quite impressive, as it reaches heights up to 50′ under average conditions – although this can be mitigated by growing it in a smaller container (#3 pot). This native of the West Indies and Central America features simple leaves, up to 10″ long. Zone 10.
Passiflora x ‘Lavender Lady’ (Syn. ‘Amethyst’) – This old hybrid is often sold as a hardy, but is best grown in a large container with a mini-trellis and overwintered in a cool (but frost free) sunroom or greenhouse. The clear lavender-purple blooms are borne from late spring to autumn. As with all passion flowers, they should be pruned in growth and not when they are dormant. Zone 8 hardy.
Passiflora incarnata – Maypop, as it is commonly known, is native of the southern United States and is herbaceous in nature. It needs a very well-drained site (with less fertile soil) and produces fragrant white, mauve or lilac flowers. This is probably the hardiest of all the passion flowers, and it is an important medicinal plant in the control of Parkinson’s Disease. Zone 6 hardy.
Passiflora x ‘Purple Haze’ (P. caerulea x P. amethystina) – A relatively new hybrid with 2.5-inch wide fragrant mauve blooms borne continually from late spring to autumn. The corona filaments are wavy and deep purple at the base, with a white band, and then mauve at the tips. This passion flower would be another good specimen for container culture. Zone 9 hardy.