The spicy, edible root called wasabi can be ground into an even spicier green paste that's served with many Japanese foods — and is also called wasabi.
Watch out for the wasabi sitting innocently on the plate beside your sushi! It may look like a blob of avocado, but it tastes pungent and deeply spicy. The flavor and spice of wasabi is often compared to horseradish or spicy mustard; you don't feel the heat on your tongue so much as in the back of your nose. Sometimes the Japanese plant is unavailable and horseradish root is used instead — sushi chefs call this "Western Wasabi."