I've tried every technique and I can't get my passion fruit seeds to germinate I tried acid, milk, soaking, scarifying, peroxide, paper towel technique,soilless dirt, mulch and still can't get it to germinate. I tested the seeds and the were viable.
The varieties I planted were:
Passiflora edulis- Purple Passion Fruit
Passiflora edulis - Red Passion Fruit
Passiflora edulis var. flavicarpa- Lilikoi
What's odd is that I live in zone 10a -b its very warm.
I also found the germination rate to be on the low side. That said, i had some guavadilla seed that didn't germinate, and got chucked in a flower pot (just in case). They germinated the next year, and I ended up giving plants away...
I juice my passion fruit after they have shrivilled and plant the seeds directly into small plastic cups with seed starting mix. I had 100% of the seeds germinate within 2 weeks. In my opinion they germinate faster when they are fresh instead of cleaned dryed and stored. I even leave some pulp on them and they perform just fine.
I also use the fresh seed. I will put the pulp on a paper towel for a couple of days to dry up the juice sacs and then put on top of a pot of potting mix. Usually have a pot full of seedlings in a few weeks. grown outside because of living in a warm climate. aloha
I have planted fresh seed from two different species of passies and had to wait a long time for them to germinate/come up. I don't have any secrets to share as such, but I do know that they need warmth to germinate. I am puzzled by FL not being warm enough. I just used fresh, sterile mix and small starting pots in plastic bags. I fall planted maypop seed indoors as described and did not see plants until late March the next year. I'm wondering if just pressing onto the soil surface and exposing to light might help instead of planting under the soil?
I grow Passi's and Pipevines from seed, and they seem to be very similar. Soak as you've been doing. Use a peaty seed starting mix, and just press into the surface and cover with a fine layer of crushed vermiculite. ( I run mine thru a sifter). Keep on a heat mat at least 80-85º. Do not let the surface dry out. The fresher the seed the better, but I've had seed that was a year old germinate in 30 days, and fresh seeds take 3 months. They are a PIA, but sometimes the only way you can get the different varieties is to try them from seed.
That being said...I too have tossed some starter cells and low and behold when I was least expecting it up they came !
I obtained P. edulis 'Whole Foods' (i.e. seed from a purple fruit I bought at Whole Foods)
and four types of Passiflora seed (three edulis/edulis v. flavicarpa, and one P. mollissima) from rareexoticseeds.com.
The 'Whole Foods' seeds was cleaned and stored a week before attempting germination of a damp paper towel in a baggie. After 6 weeks 20 seeds had a germination rate of 0%.
I also treated all five seed types of 24 hour 3% peroxide soak followed by a 24 hr 500 ppm Gibberellic acid soak, then planted them in Miracle Gro potting soil.
Result: 50-100% germination in 1-2 weeks for the four from rareexoticseeds.com, and 50% from the 'Whole Foods' at about week 3.
My impression was that the fresh seed had a germination inhibitor that fades with (some) storage given the lag in the 'Whole Foods' lot.
The two things that you need to germinate tropical Passion fruits is HOT WEATHER, but mainly FRESH SEEDS.
In my area the summer is very hot, and Passiflora Edulis seeds germinate very easy after the average temperature has reached the 70's.
So, a heated seedbed may be needed in case of cooler weather.
But the most important factor for their germination is FRESHNESS.
The best way is to get seed from fresh fruit, dry them in the sun, and sow them soon.
I have noticed that Passiflora Edulis seeds remain viable for less than one year, so NO ORANGE JUICE OR ANYTHING can make them viable afterwards!
I think that seed traders write about "challenging" or "erratic" germination just because they don't always provide fresh seeds.
These seeds must have a very short expiry date.
From fruit i have easily succeeded germinating Passiflora Edulis, Passiflora Edulis var. Flavicarpa and Passiflora Ligularis (a cool grower passion fruit).