Yakushima is famous for its nature but it is also well known for its local produce. You will come across these products all over the island in any souvenir shop and you should try them at least once to get a real taste (literally) of Yakushima.
Here are the most common specialities:
There are two main Shochu breweries in Yakushima: the Miitake 三岳 brewery and the Hombo 本坊 brewery. They both brew distilled alcohol made from sweet potatoes and are hugely popular among drinkers in the south of Japan. You can take a 30 min tour round the Hombo Shochu distillery in Harumaki, Anbo.
Yakushima has a perfect climate to grow tea and hidden behind the trees there is row upon row of tea fields. The leaves are harvested in March and you will find tea products all over the island. It does really taste delicious.
Tankan and Ponkan oranges are a mainstay of the Yakushima economy. You can find out more information here. One of the most common products to find in Yakushima shops is Tankan or Ponkan juice. It's a little pricey but tastes great.
For more information about Yakushima - check out the one and only Yakushima: A Yakumonkey Guide