Not a potato. It is a cool post-post-structuralist idea created by Gilles Deleuze and Felix Guattari.
There's no point planting rhizomes in your garden, because they only grow out of an eternally deferred centre, maybe.
A horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes. Students of Naropa University are obsessed with the rhizome, as it fulfills their dual lust for metaphor and salad.
"Rhizome, an underground stem bearing roots and flowers, and a postructuralist metaphor for nomadic traits, is a trope that Anne Waldman exploits to describe hybrid, cross-genre poetics and intuitive constellations." It also makes a decent tea.