Herb Similar to Horseradish

What herb is similar to horseradish?

The Japanese have a herb called "wasabi" that is very similar. Wasabi roots produce a green paste condiment that is very acrid just like European horseradish. Wasabi served with virtually every sushi dish.
Wasabi is a hardy perennial but requires special cool, moist conditions shade or partial shade. In Japan the best wasabi is grown in or near running water.
Wasabi plants are hard to find but Richters is researching how to grow and reproduce this plant for eventual sale through our herb catalogue. We are hoping to have plants available starting with the 2004 season.