Ōgonkan - Citrus flaviculpus hort.

Scientific classification

Kingdom:        Plantae

(unranked):     Angiosperms

(unranked):     Eudicots

(unranked):     Rosids

Order: Sapindales

Family:            Rutaceae

Genus: Citrus

Species:           C. flaviculpus

Binomial name           Citrus flaviculpus hort. ex. Tanaka

Ōgonkan (黄金柑 "golden citrus"?) or Ki-mikan (黄蜜柑 "yellow mikan"?) are the common names for a small sized variety of Japanese citrus, whose rind is of a characteristic "golden" bright yellow color.

The variety has been published as the species Citrus flaviculpus by Chōzaburō Tanaka in his 160-species scheme, but this is considered an effort of a "splitter," as opposed to Swingle's classification system which is generally preferred in the West.

Alternate spellings (romanizations) include "Ougonkan" or "Ogon-kan". It has also been called "Golden orange" in Kanagawa Prefecture.

The variety has long been known in Kagoshima Prefecture as Ki-mikan (黄蜜柑 "yellow mikan"?) but, precise origins are unknown.

According to one assertion, it has been known in Higashi-ichiki-chō (ja) and its neighborhood (now Hioki, Kagoshima) since the Meiji Period.

Anecdotally in this Hioki area, it has been told that the variety was either introduced by the Jesuit Francisco de Xavier, or brought back from the Korean Peninsula during the campaigns in the late 16th century (Hideyoshi's invasions of Korea).

It has been suggested that the name "Ōgonkan" was dubbed by Harutarō Muramatsu (村松春太郎?) who introduced the variety to Ehime Prefecture,[citation needed] but this too is poorly documented.

The small fruit has a diameter of 4 to 5 cm, weighing 60 to 80 g. The rind, which is bright yellow, can be peeled by hand but with difficulty. It issues a distinct fragrance, and is considerably sweet tasting, with some balancing acidity. Harvested from February to April. Seedless (Self-incompatibility) traits have been observed.

Its fragrances is similar to the Hyuganatsu, which is another bright yellow citrus that is larger-sized, but somewhat sweeter by comparison. And like the Hyuganatsu, the white pith (albedo) may be eaten.

The rind's cold-pressed oil has been studied for fragrance factors, and was found to contain limonene (roughly 80%), followed by the monoterpene Gamma-terpinene (10%), trans beta-farnesene, and myrcene, showing similarity to Hyuganatsu's peel profile, though with quantitative differences in concentrations.

According to government (MAFF) statistics for FY2010, crop yield of the Ōgonkan totaled 137.3 t (metric tons) in all of Japan, with 108.2 t shipped to market, none of it classed as processed goods (i.e., juices, etc.) in the statistics. Kanagawa Prefecture produced 93.4 t, representing 68% of the national total, followed by Shizuoka Prefecture with 25.0 t (18％), Ehime Prefecture with 13.9 t, and Kōchi Prefecture with 5.0 t.

Major cultivating areas listed are Odawara and Yugawaracho (Kanagawa pref.), Numazu, Shizuoka, Uwajima, Seiyo, Imabari (Ehime pref.), and Kōnan, Kōchi.

The Ōgonkan was the pollinating parent for the hybrid cultivar Hime-Koharu (媛小春?) developed by Ehime Prefecture, and was the seed parent of Shonan Gold developed by Kanagawa Prefecture.