Just What Is a 'Shiranul'?
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 'Shiranol' is so low in acid content that is promised to be many times sweeter.
Shiranol is a seedless, sweet variety of mandarin orange.
'Shiranol' is a Japanize hybrid (1972) between a Ponkan Tangerine and a Klyomi. Klyomi is a cross between a Trovita and a Satsuma. So officially, Shiranol is a hybrid of Ponkan, Satsuma and Trovita (another sweet orange in Japan).
Shiranul 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 'Shiranul'. 'Sumo Mandarin' is another trademarked name for 'Shiranul'. In South Korea, it is called 'Hallabong'. In Brazil, it is known as 'Kinsei'.
Shiranul / 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'.
GROWTH & FRUITING HABIT
Shironol 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 from December to January, much like the Ponkan, but later than the Satsuma.
In Brazil, 'Kinsei' is harvested from May to September.
Shironol 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 Shironol is a more tempermental 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.