Fresh wasabi, is an expensive luxury item in Japan .The best wasabi , wild wasabi ,grows high in the mountains in cool ,clear ,shaded ,shallow streams of spring water .The root ,green in colour is grated and mixed with the soy sauce dip for sashimi.Greated wasabi is also placed between the rice and fish in nigirizushi.The powdered version ,is wetern horseradish , with green coloring and some mustard powder added .Outside Japan ,tubes of wasabi – paste or powder form are available.