The worlds largest radish is the Sakurajima Radish aka shimadekon, giant daikon, Sakurajima island giant radish, or jumbo daikon. Sakurajima Radish is a Japanese heirloom that holds the Guinness World book of records title weighing in at 68 lb 9 oz, although the average Sakurajima Radish weighs between 10 and 13 lbs and about 18 – 20 inches in diameter.
It is a rounded variety, as opposed to some of the longer and more slender Japanese Radishes, it is also white and has a milder and somewhat sweeter taste than standard radish varieties. It is crisp and low in fiber.
There are several sub-varieties whose primary difference is the maturation time – early, middle, and late. The late maturing varieties are the most common.
They originate in a volcanic endowed rich fertile soil of Japans Sakurajima Island, but are grown elsewhere successfully.
Germination 8 – 10 days
Germination Temperature 55 to 75 degrees F
Maturity 80 to 90 days
Loamy and clay soils with reasonable drainage
Soil pH ph 5.5 to 6.8
Sakurajima Radishes are not frost tolerant and must be planted out after the last frost date in your region
Pinch off the tops as they mature to prevent bolting, which destroys the flavor.
Don’t plant radishes in the same bed a cole crop has recently grown – the last three years. Incorporating wood ashes into the soil will discourage root maggots.
Avoid excessive organic materials and manure or fertilizers that are high in nitrogen. Excessive nitrogen will encourage lush foliage at the expense of the roots.
Related: Growing Radishes Hydroponically