Hassaku orange - Citrus hassaku hort.

Hassaku orange (Japanese: 八朔) is Japanese citrus hybrid similar to an orange in color but with the size of a grapefruit.

It originated in Hiroshima prefecture, but now Wakayama produces around 70% of the country's yield.

The Japanese eat the Hassaku as an orange, but it can be eaten with a grapefruit spoon to avoid the bitterness of the residual albedo. It is much more tart than an orange, but it does not lack sweetness entirely. When bitten into, juice bursts into the mouth from a slice of this fruit, considered very pleasant.

In 2010, 68% of Japan's 35,919-ton hassaku harvest came from Wakayama prefecture, with the remainder mainly grown in Hiroshima, Ehime and Tokushima prefectures.

The fruit is mostly eaten raw, because, when cooked, it becomes more bitter. Currently, the idea of using ion-exchange resin is being suggested as a way to remove the bitterness, and so make it possible to commercialize the juice. Nutritionally, the fruit is a good source of vitamin C, folic acid, potassium and fiber.

Parentage/origins: Parents unknown.

Rootstocks of accession: Carrizo citrange

Season of ripeness at Riverside: October to November

Thermotherapy to remove tristeza. Hassaku is probably of pummelo-mandarin parentage with pummelo predominant.

Fruit medium-large (9-10 cm in diameter), slightly oblate; both ends somewhat depressed; seedy and monoembryonic. Rind color orange-yellow; medium-thick; surface somewhat coarsely pebbled; moderately adherent.  Segments numerous; axis large and semi-hollow at maturity.

Flesh color light yellow; somewhat coarse-grained; lacking in juice; flavor good.  Early midseason in maturity and stores only moderately well.

Tree vigorous, upright, virtually thornless; leaves large and pummelo-like, but petiole wings narrower, approaching sweet orange.

Hassaku is said to have originated as a chance seedling in Hiroshma Prefecture, Japan.  It was noted and named in 1860, but was not propagated and planted commercially until about 1925.

In 1964, Japanese planting was reportedly in excess of 2,500 acres, mostly in the prefecture of its origin.  During the 1960's, however, it has been planted increasingly elsewhere.

Its characteristic strongly suggest pummelo-mandarin parentage with pummelo predominant.

Availability: Commercially available in California in Citrus Clonal Protection Program.