the mutual intelligibility barrier between humans and plants makes it impossible to know whether the concept of democracy is supported by the plant kingdom or not
Plants have no proven sentience and ability to communicate their vote. As they are unable to vote -- and will never be able to vote -- there is no reason to give them voting rights.
Plants cannot communicate with humans and vote in an eligible manner, nor can they assist in the right to govern. They should be granted, however, the right to assemble plant governments and restrict Venus fly-traps (also known scientifically as Trumptraps) from fucking everything up.
Plants are diverse living beings which inhabit every country on Earth. Politics affects them (Evironmental policies, agricultural and technological development, transportation, etc.) in a very direct way and thus they should have a say.
A population is a group of individuals of one species that live in a particular geographic area where as a community is all the organisms that inhabit a particular area; an assemblage of populations of different species living close enough together for potential interaction.