Hi,
Currently I am growing a number of strains of improved Passiflora incarnata AKA Hardy Passionfruit, Maypop, etc. I am seeing some pretty amazing improvements in flavor, size, and juice content.
I’m wondering if anyone has tried hybridizing this species with other tropical cousins such as P. edulis, etc? Do any of the tropical passionfruits flower and fruit rapidly from seed? P. incarnata can flower and fruit within 6-8 months of seeding. It appears the tropical varieties take longer, which may make hybridizing more challenging. Any thoughts or growers of superior P. incarnata out there?
What a cool breeding project! I have no idea what their pollination requirements are, but I would think a good strategy would be to try to get as many tropical/subtropical passion fruit cultivar flowers/pollen to use them as pollen parents for your improved passionfruits. Since yours are already fruiting age you could start your f1 generation quickly and start selecting for hardiness. Excited to see where this goes!
There’s been about 50 years of work that’s gone into various attempts. In general, while many crosses are possible, results have been very mixed.
First gen P. cincinnata x incarnata is fairly easy to find. Incense is the easiest to get ahold of. It is fairly vigorous. Blue Velvet is similar, but supposed to bloom more.
P. edulis x incarnata is hard to find. Grand Tiara, and Byron Beauty are some I have heard of.
Tetraploid P. cincinnata x incarnata includes Inspiration and I believe Temptation.
Tetraploid P. edulis x incarnata includes Ugly Betty and probably others.
Complex hybrids include Marjorie Sherwin, Jim Neves, Bucky, Blue Eyed Susan, among others.
This is just from my notes, so you’d want to verify the actual varieties here.
In general, the best cold hardiness of these hybrids is zone 8. Perhaps a backcross to maypop would improve that, but there are other considerations. First and foremost being, you’re going to want to be working with tetraploids. Most of what I’ve read suggests that fertility is quite low in diploid hybrids with incarnata. My own experience with hybrids is that they set seed well, but my experience is limited to tetraploids only. Tetraploids also tend to have improved fruit and flower qualities.
While P. edulis is the most common commercial variety, it is evergreen. Hybrids with P. cincinnata benefit from the fact that it, like maypop, dies back to the roots each winter, which greatly improves hardiness.
That being said, in order to backcross, you’d need a tetraploid maypop. Alba Supernova is, and there are probably others. But run-of-the-mill maypops are diploid.
There are some P. incarata x caerula hybrids, but I’d avoid them, as P. caerula. is described as nonpalatable. P. tucumanensis I’m less sure of.
There’s an ebay shop called passiflorista who carries a lot of incarnata hybrids. He sold me the ones I have. Hardiness is going to be your biggest issue if you pursue hybrids. Growing season length may be an issue for you as well.
“Based on the results of this study, there is reason to be cautiously optimistic about interspecific hybrid Passiflora involving P. incarnata. Creating more generations with backcrossing to P. edulis is the next logical step in the process.”
Wow lots of great replies so far. @a_Vivaldi are any of these hybrids capable of edible and desirable fruit production? It sounds like a lot of the efforts have been to produce ornamental passionfruit plants.
Great info on tetraploids also. Could I use hormones to produce a tetraploid? How does a tetraploid occur?
Anything with incarnata, edulis, or cincinnata parentage should be edible, caerula not so much.
That being said, there’s no guarantee that the fruit will be adequately sweet, juicy, or well filled. The hybrids I was able to try this year were good, but I’m withholding final judgement until next year at least. I suspect they will be sweeter and more aromatic, but we’ll see. They were very slow to ripen, and the seeds weren’t any smaller than maypop. But they are vigorous, fragrant, and floriferous.
I’ll be honest, I don’t think hybrid passionfruit for fruit production are a realistic goal outside of zone 8 or so, at least from what I’ve read about the current hybrids. Ornamentals would be a much easier target to my mind, both in terms of hardiness and in terms of getting something worth commercializing. But I’m far from an expert, nor am I actively breeding passiflora.
Mr. August Kehr published an article on treating a flat of seedling plugs all at one time. Maybe upside down? only on the growing foliage. I read it years ago, don’t know how to find it.
There is a Facebook group called “Cold Hardy Passiflora” that is focused on creating and testing cold hardy passion flower hybrids. P. incarnata, P. tucumanensis, P. cincinnata and P. caerulea are the most prominent species. Tucumanensis also has cold hardy roots and reemerges in spring like incarnata, P. careulea is evergreen but less hardy. Tucumanensis has smaller fruits that ripen faster than incarnata, caerulea fruits also ripen but are bland.
Raphael Maier from Lubera, a large Swiss plant nursery, currently has a large breeding program going on, based mostly on P. incarnata. He has also released a book on the topic.
I can say that lutea, citrina, capsularis and other bat-winged passiflora will not cross pollinate with incarnata. (lutea is claimed to be the hardiest passiflora)
A shame as capsularis flowers and ripens fruit for me in a single season from seed…
