65 to 80 days to maturity. Raphanus sativus. Big Time Korean Radish Hybrid Seeds. Hybrid, cool season annual. Big Time Korean radishes, unlike other Korean radishes, are a spring season radish that can be planted early in the season. They have deep green shoulders that fade into bright white roots. These mild, delicious radishes grow up to eight inches long and three inches in diameter, and every bite is perfectly crisp. Big Time radishes are easy to grow, too–they are resistant to bolting and have a great heat tolerance! Approximately 3,200 seeds / oz.