Citrus reticulata ‘Shiranui,’ better known by the common name “Shiranui Mandarin Tree,” is a plant that will supply you with some of the most delicious citrus fruits you can find. During the winter months, this tree will carry plenty of large mandarins that will be full of juice and without any pesky seeds. And although this plant thrives in the warmer regions of the world, its small size allows for overwintering as well.
I. Appearance and Characteristics
Shiranui is a variety of mandarin that was developed by researchers working for the Japanese government back in the 1970s, according to Citrograph Magazine. It was officially named Shiranui but also later gathered other names, such as Dekopon and Hallabong (in Korea).
Shiranui budwood was eventually imported into California, legally and illegally, by numerous people. According to David Karp, writing in the Los Angeles Times in 2011, the most important importation was done by Brad Stark in 1998, as it was his budwood that led to Sumo. A company in California’s Central Valley called Suntreat bought the rights to Stark’s legal Shiranui budwood and assembled a club of citrus farmers to grow the trees and sell the fruit under an exclusive and confidential agreement. If anyone asked about their trees, they were to call them “XP1”. But once they started selling the fruit in 2011, they would call them “Sumo”.
Shiranui fruit are big for mandarins, but they’re not true mandarins. They are said to come from a cross between a Ponkan mandarin (specifically, Nakano number 3) and Kiyomi tangor; a tangor is a “tang-or”, a tangerine (mandarin) crossed with an orange. In size, Shiranuis are between a typical mandarin and a typical orange.
But the most remarkable characteristic of a Shiranui fruit is its neck. Most (not all) Shiranuis have a protrusion at the top, which comes in handy at eating time because it can be popped off to start the peeling.
II. How to Grow and Care
Sunlight
The Shiranui Mandarin Tree requires a growing location that receives full sunlight each day.
Watering and nutrients
In most cases, it is best to water the Shiranui Mandarin Tree about once per week during periods of active growth. Alternatively, you can water this plant whenever you notice that the first two to three inches of soil have dried out. Watering more frequently than that can lead to overwatering. This plant also performs best with regular feedings. Apply a citrus-specific fertilizer or one that is higher in nitrogen about once every two months during the spring, summer, and fall.
Pollination
Pollination is of the utmost importance for anyone who wants their Shiranui Mandarin Tree to produce fruits. Thankfully, this plant is self-fertile, which means that a single plant can produce a viable harvest on its own. However, if you plant multiple plants, allowing for cross-pollination, you can expect the harvest to be larger. A Shiranui Mandarin Tree growing outdoors will attract pollinators, but those growing indoors will likely require hand pollination. To perform hand pollination, use a small paint brush to manually move pollen from the male flower structures to the female ones.
Planting Instructions
Those living in hardiness zone nine or warmer can plant their Shiranui Mandarin Tree in the ground by digging a hole that is as deep as the root ball is tall and about twice as wide. Anyone in a colder region should grow this plant in a well-draining container and bring it indoors when the temperature drops to 30 degrees Fahrenheit. In either case, your Shiranui Mandarin Tree will appreciate at least six hours of direct sunlight per day and well-draining soil.
Pruning
You can prune your Shiranui Mandarin Tree any time during spring, summer or fall. When you prune, make sure that you use tools that are sharp and sterile and that you remove any branch that is dead, damaged or diseased. For this fruit-bearing plant, you should also remove branches that grow at a narrow-angle to the trunk since they will be less capable of carrying the weight of heavy fruits. It is also beneficial to thin the canopy of this tree and remove suckers that emerge from the base.
Pests and Diseases
Overall, the Shiranui Mandarin Tree has decent resistance to pest infestations. However, it remains possible for an infestation to occur, and when one does, it is likely the result of aphids, scale insects or mites. However, these issues are often avoidable and easy to manage when they do arise. The most common disease to threaten the Shiranui Mandarin Tree is root rot, which occurs in excessively moist soil conditions. To avoid this, ensure the soil and container in which your plant grows allow for excellent drainage.
III. Harvesting and Storage
The fruits of the Shiranui Mandarin Tree will usually be ready for picking during late fall or the winter months. You will know that a fruit is ripe when it has grown to a considerable size and has lost all of the green colors on its rind. Ripe mandarins will be entirely orange in color. When it comes time to harvest, you’ll find that it is very easy to remove fruits from your Shiranui Mandarin Tree. While it may be possible to remove the fruits by hand, the best method is to use a pair of pruning shears.
