About Watermelon Radish: The Watermelon radish is a type of Japanese winter radish also known as a "daikon," which simply means "large root" in Japanese. Daikon radishes account for the largest percentage of any cultivated vegetable in Japan, and can be found in some form in nearly every meal of that country. Watermelon radishes, which orginated in north China near Beijing, are often served sweetened there as a dessert or fruit.
Watermelon Radish Germination: Since Watermelon are winter radishes, they should be planted about two months before the first expected fall frost. Plant them in very rich, deeply worked up soil about 1/2" deep and 1" apart; later, thin the seedlings 4-6" apart.
Growing Watermelon Radish Seeds: Radishes do well with consistently moist soil and the addition of organic matter such as compost. Do not allow the soil to dry out, but also avoid overwatering as this can cause splitting.
Harvesting Watermelon Radish: Watermelon radishes can be harvested at any time up to their mature size of 3". The flavor is sweet and crisp; they also store well for the winter.
Saving Watermelon Radish Seeds: Radishes will cross pollinate with all other varieties of radish, and must be isolated by at least half a mile from other varieties to protect genetic purity. Allow the radish plant to fully mature and send up a flowering stalk; the pods will form and turn from green to brown. Pick the brown pods and allow them to dry for several days. Thresh out the seeds by opening the pods by hand, or by applying pressure to crush them. Store the seeds in a cool, dry place for up to five years.
Detailed Watermelon Radish Info: Raphanus sativus. Also called Beauty Heart, Rose Heart, or Red Meat. Biennial. 55 days. 2,500 seeds per oz. 4-6" height. 2-3" spacing. Produces 2-3" greenish white skinned, round radishes with red flesh.