The term “Rainbow Poplar” does not refer to a separate wood species, but rather, is a designation of Yellow Poplar (Liriodendron tulipifera) that has been mineral stained. The resulting mineral stained wood—which, although not necessarily common, is by no means rare or scarce—exhibits a variety of colors ranging from green, purple, black, red, etc. It is this distinct variety of colors that turns an otherwise oridnary piece of Poplar into the intriguing Rainbow Poplar. The precise cause of these streaks and discolored wood produced in certain trees is not fully understood.
See the page on regular Poplar for more information on mechanical and working characteristics of the wood.
A special thanks to Mike Leigher for providing the wood sample of this wood species.