Groundnut

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As common names go, groundnut doesn't quite seem fitting for such a distinctive plant. Known scientifically as Apios americana, this leguminous vine can be found growing along ecotone boundaries throughout much of eastern North America. It becomes most obvious to passers by from July through September when it is flowering. 

Okay, to be fair, groundnut is a fairly accurate description. Not only are the seeds of this vine edible, so too are the starchy tubers it grows from. However, I think this all detracts from a rather intriguing ecology. Populations of groundnut occur in one of two forms - diploid (2 sets of chromosomes) or triploid (three sets of chromosomes). It would seem that eastern populations mainly consist of this triploid variety. 

The odd thing about it is that triploid plants are sterile. Though they produce seemingly functional flowers, they never produce seed. Instead, these populations reproduce vegetatively via their underground tubers. Other than their lack of reproductive ability, there doesn't seem to be any other noticeable differences between diploids and triploids. 

Speaking of reproduction, there seems to be a bit of mystery concerning the types of pollinators targeted by this vine. The flowers, with their carrion-like appearance and strange odor, would seem to suggest carrion flies. Some authors are rather set on this hypothesis despite very little evidence. A more thorough investigation into the pollination biology of groundnut revealed only visitors to be bees. Regardless, when insects of a certain size land on the flowers they trigger the release of the anthers, which slam into the insect, dusting it with pollen. This is a very similar strategy to a closer relative of groundnut, alfalfa (Medicago sativa), which is most definitely bee pollinated. 

Despite all of the confusion surrounding groundnut, it is nonetheless a great species. It fixes nitrogen, provides food for humans and wildlife alike, and looks really cool to boot. This would be a great addition to a native plant garden throughout its range. 

Further Reading:

http://link.springer.com/article/10.1007%2FBF00994096?LI=true#page-1

http://link.springer.com/article/10.1007%2FBF00985913#page-1

http://www.cnhp.colostate.edu/download/documents/2001/Apios_americana_Report2.pdf

http://plants.usda.gov/core/profile?symbol=APAM