Sakurajima grows to about 20 inches in diameter in good soil, and the globe-shaped roots can approach 100 pounds. The flavor is best when the radishes reach only six to eight inches in diameter. That’s maybe a little too much radish for me, and I’ve been doing well this winter on the smaller Miyashige, some of which did reach the size listed on the packet — about 18 inches long and three inches across.