"What is the difference between the Japanese green teas such as sencha, shincha, kabusecha, fukamushi-cha, and gyokuro?"

Right: Kabusecha growing under 45% shade - The main difference between the various Japanese green teas has to do with the way each is grown and or processed, the growing locality, and with the respective conditions imparting a different taste. In general, the earlier in the season the green tea is harvested, the better the quality. The very first harvest occurs near the end of April to early May, and is known as shincha, or in english as the first harvest or first flush.
Sencha is grown in full sun, while Gyokuro is grown in the shade. Kabusecha is also grown in the shade, but not to the same degree and length of time as gyokuro, giving it a taste somewhere between the two, although in reality it's closer to sencha. Shincha or "new tea" in Japanese, is that green tea which comes from the very first harvest of the of the growing season, and which also is not put into cold storage but instead is immediately packaged and released for sale. Shincha is only available from May ~ July or as supplies permit. It tends to be expensive, as it contains the highest vitamin and polyphenol contents.
Fukamushi Sencha, known in Japan as Fukamushi-cha, it sencha which is steamed for a longer than normal period of time during it's processing. This green tea is often grown at lower elevations. An expert tea grower will steam his tea according to the right conditions for each individual yield, and much knowledge and experience is required in order to adjust it just right. Fukamushi-cha tends to have a thicker, cloudy consistancy and the loose leaf is finer.
Uji-cha, or Uji green tea - While most Japanese green teas are grown in Shizuoka, the small town of Uji, located near Kyoto, is known throughout Japan as producing some of the highest quality Japanese green teas available, and is thus known as "Uji-cha". O-Cha.com is proud to be a supplier of Uji green teas from Japan's oldest tea shop, Tsuen Tea.
The quality of green teas in Japan varies considerably, and the taste is quite different between the varieties with each having it's admirers who prefer one over the other. If you have not yet done so, consider trying Japanese green tea today!