Passiflora breeding

I have an extremely niche question that I'm hoping someone can point me towards an answer.

The crux of my question is what subgenus is P. lutea in and what subgenus(es) are P. edulis, P. caerulea, P. incarnata in?

P. lutea is hardy to zone 5 here in the US. P. incarnata and P. caerulea are hardy to zone 6. Tropical P. edulis hardy to zone 9.

The goal for many decades has been to develop a cold hardy hybrid that can produce large fruits like P. edulis. Several hybrids between P. edulis, P. incarnata and P. caerulea are available.

But I can find no attempts to create any hybrids using P. lutea.

I've found anecdotal information that Passiflora species can only interbreed within their own subgenus.
While the four Passiflora subgenuses (subgeni?) are referenced in Wikipedia, it is not clarified what species are in which subgenus.

So the implication is that P. lutea cannot breed with the other three, but I have no information clearly stating that.

It appears Passiflora lutea is Decaloba subgenera.  Per info I found on http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=124132
The flora area includes species of only the two largest subgenera: Passiflora, with relatively large flowers and fruits and a predominant chromosome number of n = 9, and Decaloba, with relatively small flowers and fruits and a predominant chromosome number of n = 6
I am wishing you luck!
David

Thanks David, that's what I needed. So it looks like it's unlikely that I will be able to cross lutea with any of the other three. But I'm interested in having them in the garden regardless, so I'll give it a shot but won't keep my hopes up. Thanks for your help.

Well I'm on to new ideas since I now have lists of what species are in what subgenuses (subgeni?).

According to this site,
http://www.mobot.org/mobot/research/passiflora/Supersect_Decaloba.shtml
Passiflora quadrangularis, the giant grenadilla, is also in Decaloba like my plucky little P. lutea.

P. quadrangularis has the largest fruit of all passionflower species and is hardy to zone 10.

P. lutea has grape sized fruit and is hardy to zone 5.

So a theoretical hybrid between the two could be hardy to zone 7 (where I live) and have a reasonably sized fruit.

Thoughts?

I like your idea Alexander.  I'm just curious, can you eat P. lutea whole like a berry and is it very pleasant or do the seeds and coat distract from the experience?  I'm just wondering because perhaps breeding for heavier "berry" production would also be very worthwhile.  I'm very curious about this plant now, thank you!  I love the idea of "passion berries" :)

Thanks Greg,

Unfortunately I found that P. quadrangularis is not in subgenus Decaloba, so that cross is impossible.

I have not yet tried the fruit of P. lutea but it was deep purple and very aromatic with herbal, earthy and dark berry tones.

My most recent research has led me to look at P. incarnata (aka Maypop)(zone 6), P. caerulea (zone 6), and P. quadrangularis (zone 10). All three are in the same subgenus.

Incarnata and caerulea have a well known hybrid called Colvillii which is noted as surviving temperatures as low as -15F, which corresponds with zone 5.

Caerulea and quadrangularis have a hybrid called Allardii, but what little info I could find was contradictory and in some places it was noted as being sterile.

I could not find any records of P. quadrangularis being crossed with either P. incarnata or P. colvillii. But whether this because no one has attempted it is impossible is hard to say.

So my latest plan is to try all three crosses and to see what works;
P. incarnata x P. caerulea
P. incarnata x P. quadrangularis
P. caerulea x P. quadrangularis

Depending on what viable offspring survive I will do further crosses to incorporate whichever species is missing.

If anyone has experience in Passiflora breeding or knows of an edible Decaloba species with large fruit, please let me know.

No answers for you Alexander, but I'm routing for you!

Now you have me highly interested in growing P. lutea.  The pictures of it in flower and fruit look so nice.  I've been unsuccessfully trying to grow maypops here in zone 5 Maine for years.  This year I'm trying some northern maypop genetics....we'll see come spring.  Maybe P. lutea is the Passiflora for me?  I've tried looking for P. lutea seeds online but so far no luck.  Anyone know of any sources?

Hey Greg,

This is the only seller of P. Lutea I've seen, but they're out of stock.
http://passiflora-shop.nl/lang-en/passiflora-species/169-p-lutea.html

Lutea is hardy to zone 5 and can be found as far north as Pennsylvania. Which if you actually look at a growing zone map of the US is somewhat contradictory since most of Pennsylvania is zone 6.

Lutea is not nearly as an aggressive grower as it's relatives and unfortunately gets mistaken for kudzu and gets pulled up here in the south, so it's actually headed towards being endangered.

My gut says Maine is too far north and any existing Passiflora would need to be grown indoors or in a greenhouse. But if it were me, I wouldn't be deterred. But I might recommend a hybrid of ambition and creativity.

I mentioned P. colvillii earlier, it is a hybrid of caerulea and incarnata which are both cold hardy. This hybrid can be found online, so you don't have to breed your own. You could grow it indoors in a large pot for a year or two to get it established and then transplant it outdoors at the start of the growing season.

The next step would be a custom hybrid. Passiflora tucumanensis is harder to find but has a hardiness comparable to caerulea and incarnata. Guglielmo Betto is an existing hybrid between P. incarnata and P. tucumanensis. So you could purchase some combination of the three parent species and/or the two hybrids, grow them indoors, cross pollinate them, harvest the seeds and then follow the steps I laid out for just colvillii in the previous paragraph.

If you can accumulate a large number of seed accessions for Passiflora lutea, it might still be possible to select for plants with larger and better-tasting fruits. I'm unfamiliar with what natural size variation occurs in wild fruit for the hardy yellow passion flower, but mutations for larger fuit should emerge under the right conditions.

In the case of tomatoes, the wild currant tomato (Solanum pimpinellifolium) has fruits not much larger than a garden pea while cultivated beefsteak tomatoes routinely bear fruit the size of softballs. A similar size difference between wild type fruits and domesticated fruits can be found in other plants; for example, squash, avocados, corn (maize), peppers (capsicum), and strawberries.

I have found an very interesting thing! Flora Toscana from Germany (https://www.flora-toskana.com/de/tropische-fruchtpflanzen/461-passiflora-edulis-colvilii-maracuja-granadilla-passionsfrucht.html) have crossed P. colvilii with P. edulis and they claim it is a great plant!

Cool to have oportunities to start in hot with my breeding experiments.

Breeding hardy passifloras! Fascinating topic. Yet it seems imperative to get fully clear on passiflora hardiness to understand the implications.

Alexander, you say:

P. lutea is hardy to zone 5 here in the US. P. incarnata and P. caerulea are hardy to zone 6. Tropical P. edulis hardy to zone 9.

and later:

Incarnata and caerulea have a well known hybrid called Colvillii which is noted as surviving temperatures as low as -15F, which corresponds with zone 5.  

Some of this is fairly contrary to my understanding. P.caerulea is sometime quoted as being hardy to zone 6 (-10°F or -24°C) but other sources such as PFAF - https://pfaf.org/User/plant.aspx?latinname=Passiflora+caerulea - state zone 9 (20°F or -7°C). A huge difference!!! What is the truth?

From seeing them only marginally surviving where I'm from in Southwest England, I'd say they're hardy to around zone 9 or probably zone 8 for well established specimens.

As for P.incarnata - it's native to states like Illinois and Indiana, so definitely hardy to zone 6 (-10°F or -24°C).

A hybrid between the two, then, would seem unlikely to be more hardy than either. You mentioned the hybrid P.colvillii is hardy to zone 5. I would simply love for that to be true, since I now live in zone 5 Latvia! But a quick search at https://www.passiflora.it/colvillii/246/eng/ tells it's only hardy to -10°C (zone 8).

It would be lovely to cut through all the conflicting information by getting real, first hand experience from growers - which exactly is what makes permies forums so great! So let's have the truth about hardy passifloras y'all!

https://www.ourfigs.com/forum/blueberry-home/1238943-my-ontario-non-fig-experiments/page2#post1407769

P. Caerula and Incarnata are being grown in Ontario here. Both seem to come back from the ground.  THis is zone 5.

I am growing p. Incarnata in zone 6 massachusetts. It grows as an herbaceous perennial, but is very vigorous.

Hi Brendan,

Welcome to Permies.

Kārlis Taurenis wrote:Breeding hardy passifloras! Fascinating topic. Yet it seems imperative to get fully clear on passiflora hardiness to understand the implications.

Some of this is fairly contrary to my understanding. P.caerulea is sometime quoted as being hardy to zone 6 (-10°F or -24°C) but other sources such as PFAF - https://pfaf.org/User/plant.aspx?latinname=Passiflora+caerulea - state zone 9 (20°F or -7°C). A huge difference!!! What is the truth?

From seeing them only marginally surviving where I'm from in Southwest England, I'd say they're hardy to around zone 9 or probably zone 8 for well established specimens.

I'm not certain of the full range of P. caerulea, but I have seen well established plants thriving in Northern suburbs of Seattle, Washington, at least one of which was in a zone 7a spot. However, they reportedly only set fruit on years with either mild winters or early thaws.

Brendan Brown. wrote:https://www.ourfigs.com/forum/blueberry-home/1238943-my-ontario-non-fig-experiments/page2#post1407769

P. Caerula and Incarnata are being grown in Ontario here. Both seem to come back from the ground.  THis is zone 5.

I am growing p. Incarnata in zone 6 massachusetts. It grows as an herbaceous perennial, but is very vigorous.

That's my thread. I should note that that part of Ontario is more of a zone 6, and although we did get a brief cold snap down to -7F, it was an overall quite mild winter with very few lows below 10F. The freeze depth that winter was probably fairly minimal (<1ft?), whereas during cold winters it can go down to 4-5ft.

Apparently incarnata has a hardier root system. The foliage is very hardy, and seems to die back with moderate freezes in the 25-30F range (it does survive light freezes unlike truly frost tender plants such as cucurbits and tomatoes though). The stems are rather thin - I have a plant that I'm growing in a container and the base of the stem is only about 3/16" thick, compared to my other passifloras that have 8/16" (1/2") thick stems after a year of growth. This probably limits its hardiness?

Passiflora caerulea with its thicker 1/2" stems remains evergreen down to 15F, maybe even 5-10F if it only lasts a few hours and gets protection from the wind? Mine remained green after a brief drop to 11F at night, but the next cold snap (Dec 23-24 2022) was about 24 hours of continuous 5-10F temps with strong winds and only slightly milder temperatures (10-20F) for the following 72 hours. My plant was growing up the west side of a cedar tree, so it was quite exposed to cold winds.

I suspect caerulea could remain evergreen in the southern US, maybe even mid-Atlantic. New England would be pushing it, but maybe on a south wall with some protection? Or if you grow it in a pot for a year or two and then transplant in-ground in the spring so it can get really strong and established?

I've heard reports of a red passion flower in Indiana that was able to grow back from the roots, but I don't remember where it was posted or what variety it was.

I've moved to zone 5a this summer, so I think I'll be growing in containers for now.

Maybe incarnata root systems have a chance of surviving here, but the problem may be that it requires warm soil to stimulate it to leave dormancy? When I was in zone 6, they took until the very end of June to start sprouting, which doesn't give it time to grow much. My in-ground plant had no flowers and only reached about 3 ft while my potted cutting grew to 10ft with flowers and fruits.

If you think about it, incarnata is native to the southern US, where winters are cold enough to damage it (ie frosts), but you can still get warm waves in the 60s or even 70s during the winter, which could generate warm enough soils to cause many plants to sprout prematurely only to get knocked back by a spring frost. Therefore, to avoid this, perhaps maypop are adapted to only exiting dormancy once soils are really quite warm, in the 70s-80s, which signals the start of the frost free summers? And the southern US will have no trouble reaching such soil temperatures in the summer, even in April-May, since its warm season is very hot.

On the other hand, caerulea is native to tropical highlands where the climate is cooler than southern US summers and need to be able to grow/sprout in cooler soils, but doesn't have to worry about weird temperature swings where it might be 80F in early March and then 20F a week later. Therefore growth can be stimulated by cooler soils, and it is more likely to be adapted to try to withstand cold since cold is usually not too harsh or long lasting there? Whereas maypop gives up after the first hard frost because it is adapted to climates where the first frost will be followed by many more periods of cold and even harder frosts.

Nathan Yospe wrote:
I'm not certain of the full range of P. caerulea, but I have seen well established plants thriving in Northern suburbs of Seattle, Washington, at least one of which was in a zone 7a spot. However, they reportedly only set fruit on years with either mild winters or early thaws.

The key to making these work in the Seattle area is putting them in the most full sun areas of your yard and possibly changing up the soil.

These plants can handle super low temperatures. But most of them will struggle for long periods of cold and wet. Passiflora in general need soil that drains well.

I am constantly planting seeds and trying to select for things that can handle our soil better. But for those who are just looking to plant a Passiflora selection they bought somewhere, they should keep that in mind.