Seed Cotyledons germinating above ground vs below ground actually tell you if the bean plant makes tuberous/perennial roots or not. It applies to Phaseolus spp., Strophostyles spp. & even in the same species Lablab purpureus depending on the cultivar (Left is Annual & right is Perennial Lablab Bean)!
Both Runner Beans & American Wild Thicket Beans are Perennial & make Big Tuberous roots! All the other species with Cotyledons (Seed Leaves) above ground are annuals without tuberous root storage organs.
Here’s it applied to wild Fuzzybeans (Strophostyles spp.).
This is such a useful observation! I’d imagine if you made a mistake & forgot whether you planted an Annual or Perennial Bean in the wrong place, you could easily know which was which.
Plus for harvesting the root, you could mark seedlings without above ground cotyledons & know they have tuberous roots underneath.
This is WAYYY too much of a coincidence to not also apply to other beans too! So far I notice it with Bean species in the subtribe Phaseolinae, it’s possible this applies to many other species as well (In different tribes). Has anyone else also noticed this?