Self fertility in paw paws

General Fruit Growing
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read an interesting post on reddit today, claiming all paw paws are technically self fertile.

https://www.researchgate.net/publication/259547184_The_evolution_of_alternative_mechanisms_that_promote_outcrossing_in_Annonaceae_a_self-compatible_family_of_early-divergent_angiosperms

https://www.reddit.com/r/arboriculture/comments/1o6u5eh/youve_been_lied_to_about_pawpaw_asimina_triloba/ here is a link to the full post.

" Let me start this off by saying, having multiple pawpaw trees is going to greatly improve your chances of pollination which of course leads to better fruit production. But it’s false when most every grower, nursery, landscaper, etc. claims that you must have multiple trees with different genetics in order to get fruit. Different genetics is also not required, they can be clones.

They are self compatible and you can absolutely get fruit by just having a single tree, no other pollen or ovaries required! However, this is where it gets tricky. Essentially, flowers on the trees have the female reproductive organs mature first, and the flowers take some time for male reproductive organs to mature. But by the time the stamen holding pollen matures, the female ovary had closed. Every flower on the tree is either female or male at the same time, so you can see how it’s very difficult for self pollination to occur.

Now pawpaw aren’t typically pollinated by the bees and butterflies we often think of in our flowers. Beetles and flies are attracted to that foul smelling flower. These types of pollinators aren’t moving as much as bees and butterflies, with beetles often hanging out on the same plant for days.

So, imagine you’re a beetle on a pawpaw. You go into a female flower day 1, obviously you have no pollen on you. Day 2 the flowers switch to male and you get some pollen on you while you’re having your nectar lunch. Day 3, the old flowers have shriveled up but new females have opened for you to move into and pollinate. Therefore, they’re absolutely self compatible, just extremely difficult. Then you factor in wind, rain, vibration, etc. knocking the pollen off of its carrier.

Some pawpaw growers will actually self pollinate their flowers using the same q-tip day after day Loading it up with pollen to be used once female flowers emerge.

There’s also an issue with pawpaws colonizing. What looks like what may be a forest of pawpaw could just be one tree with many suckers. This is where I believe the different genetics myth comes from. All those trees would be the same plant having the same chemical reactions internally to focus on female or male flowers.

Now they typically recommend to get 3 pawpaws and I completely agree with that. Because, what if you have 2 separate trees both with mature male stamen on the same day? You’re stuck in the same boat. It could still happen where all 3 are male at the same time but the chances are less likely.

In conclusion, it’s still best for you to have 3 different pawpaw trees, just not for the lies that gardener is telling you"

Whats everyones thoughts? my first one that jumps out is im not so sure all flowers on a tree mature at the same rate like this post claims

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From your description it sounds like you’re under the impression that the flowers all open on the same day throughout the whole tree which leads to them all being female at the same time and then later all male at the same time. This is not something anyone has ever claimed that they do. They would have a mix of newly opened flowers and older opened flowers at the same time during the bloom season, so a mature tree would have plenty of pollen available at the same time as some of its younger flowers being in the female stage.

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Sorru youre misreading this. That is what i think the person who posted its misconception is

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Oh I see. The majority of the post was a quote from someone else…

I read one of the articles someone linked in the comments on Reddit and it was a study on self pollinated pawpaws. They found that seeds which formed from self pollination were smaller and wouldn’t germinate. That means that they are oddly both able to self pollinate to some extent, but also still not readily self compatible.

Edit: And now reading further in that article they’re giving a conflicting analysis in that they had high germination rate from seeds of both self pollinated and cross pollinated pawpaws… I feel like that article must have gotten published without first being properly edited for clarity. Annoying…

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Yes! It was interesting. I wonder if they instead mean that they come in flushes where over the course of a few weeks everybflower blooms, matures into male, and dies, but not staggered such as both sex of flower is available at the same time? But this was not my impression. My trees are still too young to flower

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It also appears that sunflower exhivited some self compatibility but susquehanah had none from that study

Study by ksu on the subject that we are discussing hort

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But it also said that ‘Susquehanah’ had better fruit set when pollinated by itself than when pollinated by ‘Sunflower’. That whole article would benefit from being reformatted for better clarity.

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Hm yeah. I wonder if its typos. If anyone has time emailing the professor or grad student may clarify things

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I think one of the main pawpaw peeps (maybe Timothy Lane) did an experiment on FB (or quoted an experiment) where manually pollinating a pawpaw with its own flowers (prob a non-Sunflower pawpaw) got pretend 20-30% pollination, but crossing it with another variety manually got 90%+. But leaving a single pawpaw tree without any pawpaws around (without any manual pollination) hardly got any successful pollination hence all the fruitless clonal groves in the wild.

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The confusing study we’ve been referencing indicated that cross pollination initially resulted in higher fruit set, but then also had a higher drop rate during “June drop,” after which remaining fruit quantity was similar regardless of self-pollination vs. cross pollination.

One thing I notice every time I see a picture posted of a mature pawpaw colony that doesn’t consistently set fruit is that they appear overly crowded with tall skinny trunks that have minimal branches. I’d love to see what would happen with some manual thinning to allow in more sunlight. I imagine with fire suppression culture, many of these patches aren’t getting the periodic reset that they need.

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We have some pawpaw patches in a local park that each cover nearly an acre and I believe are 100% clones. I do find some fruits in there but it’s maybe 2-3 fruits spread over hundreds or thousands of trees. It’s possible a beetle carried pollen from another one of these widely separated stands, but I believe it’s just as likely that self pollination is possible but extremely rare.

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Do you know if those clonal colonies are still flowering well, or if both flower and fruit production is minimal?

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Oh they flower like crazy. Millions and millions of blooms and only a handful of fruit.

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I would imagine that patches were managed historically for better light(more flowers), the inner bark was used for cordage so it would serve dual purpose for keeping the patches in a more productive state.

Self fertility in pawpaws exists, but as far as I know Prima is the only one that has been suggested for planting by itself(fruit isnt the best imo). Theres a lot of good reasons to plant more than one variety besides pollination anyway.

For pawpaws to keep moving forward we’re going to need bigger orchards planting out cultivar seeds/seedlings and actually evaluating them.

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I have a self-fruitful pawpaw that has reliably produced an abundant crop for the past 25+ years. This tree was shared by past pawpaw enthusiast Ed Boula who would bring root suckers to Midwest Fruit Explorer meetings. I don’t recall Ed ever mentioning a name for the cultivar or that it was self-fruitful. I’ve been calling it Boula Self-Fruitful. I expect there are many of his pawpaw trees growing in the Chicago region.
The fruit and seed are of average size. The seeds don’t appear to be viable. Critters have carried fallen fruit far and wide, consumed the fruit and passed or left the seeds, and I’ve never seen a resultant pawpaw seedling.

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Just to tip the apple cart, there are contributing factors to fertility in pawpaws.

I have 7 trees from a variety of sources, some named cultivars and some seedlings…

This year I got less than a dozen fruit in total. Many trees had none. Fruit set was the worst its been in over a decade of producing trees.

I’m not 100% sure what the issue was, but pollenation isn’t an issue for me most years (I haven’t hand pollenated for a decade), so something else is surely at work.

I hope next year is better.

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Very interesting- would be good to try germinating the seeds in a controlled environment.