I planted all my lima bean varieties side by side this year, intending to hand cross them to increase my diversity (in particular large x small seeded crosses). I just spent half an hour tearing flowers apart trying to figure out what I am working with. Has anyone else successfully hand crossed P. lunatus before? The anthers and stigma are all twisted together in a tangle that does a loop de loop for some reason, and it is almost impossible to strip the anthers without damaging the stigma. The flowers are so small I can’t tell if the stigma is even exposed in the resting position. (edit- the paper below suggests the stigma pops out of the coiled petals when depressed the right way).
Maybe my eyes were extra blurry today and it will be easier next time. I found this diagram of another Phaseolus species which seems similar to what I was seeing.
I also found this paper which is quite detailed. It seems that the pollen is shed when the buds are still green, and if you wait for them to whiten then you are too late. Also interesting is that the coiling of the stamens and pistil happens as the bud develops, so maybe I can emasculate the flowers at a much earlier stage to stand a chance. Id better prepare for weeks of squinting…
This is very tedious work, but I hope you can get successful crosses. I find these kinds of flowers do release the stigma when pressed a certain way but sometimes it is still hard to remove all the anthers that way.
Ill have another try emasculating very young flowers this afternoon. Might need a set of head mounted microscope lenses or something similar as my eyesight isnt what it used to be. Otherwise I can just try unemasculated hand crosses to increase the rate of outcrossing. Provided I can grow out all the seeds and look for off types this might be the more efficient approach.
It would be interesting if you spread pollen from flower to flower in a haphazard, speedy way and then only saved seeds from the beans opposite of the blossom end.
I’ve only grown beans briefly during one season. I could be way off. I wonder if the self pollination that happens works one bean at a time. If so, you could step in and give the plant some competition pollen to choose from for the younger beans. That would be awesome if it was true because your labor input would be way less.
The lima bean literature suggests out crossing rates can be very high, but they dont know why it varies so much. I am hopeful that the flowers will prefer outcrossed pollen, since the anthers shed when the flower is still completely wrapped up tight. Some other plants work like this, with self pollination as a last resort if no outside pollen turns up in time. I noticed leaf cutter bees on the flowers, but despite that I havent seen any obvious hybrids (especially between large and small seed types) over my years of growing the crop.
I think the only workable plan is to roughly cross mature flowers without emasculation, then grow out as much seed as possible to look for off types. I will only be crossing large x small seeded types since I want the widest cross possible, so hopefully that will make potential hybrids easier to spot. My trellising method is getting more efficient, so I think I can scale up production next year on my weedy creek flats. Lima bean seeds are large enough to climb quickly over the weeds then shade them out. Might just need a little selective weed slashing to give them the upper hand. I suspect this method will intercrop nicely with winged yams in the future too.
I was spoiled by the big chunky flowers on my sword beans last year
I love the giant large seeded forms since their vines are so vigorous once they get going. My main aim is to shift some of the diversity in my small seeded plants into the giant large seeded ones to come up with more productive/pest resistant vining types. The bush ones tend to rot on me since they drag their pods in the mud.
