Just What Is a 'Shiranui'?
While it is hard to imagine an orange or tangerine that could be any sweeter than our beloved Ponkan Tangerine aka Chinese Honey Orange, the 'Shiranui' is so low in acid content that is promised to be many times sweeter.
Shiranui is a seedless, sweet variety of mandarin orange.
HYBRID INFORMATION
'Shiranui' is a Japanize hybrid (1972) between a Ponkan Tangerine and a Kiyomi. Kiyomi is a cross between a Trovita and a Satsuma. So officially, Shiranui is a hybrid of Ponkan, Satsuma and Trovita (another sweet orange in Japan).
Shiranui is a generic name for the fruit, and what many FL growers are using as the name for this tangerine. 'Dekopon' is a genericized trademarked name for 'Shiranui'. 'Sumo Mandarin' is another trademarked name for 'Shiranui'. In South Korea, it is called 'Hallabong'. In Brazil, it is known as 'Kinsei'.
Shiranui / Dekopon was imported as budwood to California in 2005, and eventually made it to the CA fruit tree market in 2011.
It peels like a tangerine, but is considered the most sweet orange available in the States. It is so sweet, that Japan now has chewing gum with Dekopon flavor, also called 'Dekopon'.
Shiranui is sometimes marketed under the trademark 'Dekopon'
or the trademark 'Sumo Mandarin'
Shiranol or 'Dekopon' on the tree
GROWTH & FRUITING HABIT
Shironui is distinguished by its super sweet taste, large fruit and the large protruding bump on the top of the fruit (see picture).
Fruits are harvested in the US generally from February to May, much later than the Ponkan or the Satsuma.
In Brazil, 'Kinsei' is harvested from May to September.
Shironui citrus is not nearly as cold hardy as Ponkan, however. Damage temperature for the valuable fruit is reportedly at 32 degrees, so growers protect the entire plant from frost at all costs. The tree itself is most likely more cold hardy, but there doesn't seem to be a lot of documentation for it yet.
Growers also say the Shironui is a more temperamental citrus to grow, that it is not as hardy as some of our other cultivars, so should you decide to try one, be prepared to take some precautions.