Plant Polymorphisms

[Donald A. Stratton]

I am trying to compile a list of visible genetic polymorphisms that can
be easily observed in plants of the eastern US.  There must be lots of
species with known genetic variation in flower color, hairyness, leaf
spots, etc, but that information seems to be widely scattered.

So, is your favorite species polymorphic?  If so, please tell me:
  species
  polymorphic character(s)
  is the genetic basis known?
     (or discreet phenotypic classes with uncertain inheritance)
  is the polymorphism common in your area?

Thank you very much.  I will post a summary of responses to the net.
Don Stratton
dastratt at princeton.edu