Although at home and most restaurants widely use wasabi in tubes, packets, in the form of powdered wasabi and wasabi paste, they are completely different from the real wasabi. Wasabi paste is manufactured by adding green colour to horseradish as well as aromatic additives and flavours. Some of them have real wasabi (hon-wasabi) added (mostly stems or leaves) to make them taste closer to the real wasabi. (Products made with more than 50% of real wasabi are labeled as “hon-wasabi processed product”.)
Only between the root and stem of the real wasabi is used, and it has a unique strong spiciness and flavour. Most of its spiciness volatilizes easily, so the flavour is lost if it is left too long after being grated. As a tool to grate wasabi, a grater made from shark skin (in the photo) is said appropriate as it minimize the contact to oxygen and avoid drawing too much spiciness.
Although it is rare to find hon-wasabi in Australia, wasabi is grown in Tasmania. High standard restaurants in Australia purchase this wasabi, and apparently individuals can also purchase wasabi from Tasmania.
Shima Wasabi http://www.shimawasabi.com.au/