Photo: Sew Darn Jenny [Flickr]
Dutch company Happy Colors created these "tie-dyed" roses above and other multi-colored flowers by injecting pigments into the stem using hypodermic needles.
http://www.happy-colors.nl/ [in Ducth, with video clip] - Thanks quinn!
my son is a hortuculurist, can he buy them from nursuries or only by mail order?